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HARRISON'S SECTION 2: HEMATOPOIETIC DISORDERS

Complete Teaching Guide - Chapters 101 to 119

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CHAPTER 101 - HEMATOPOIETIC STEM CELLS

The Big Picture

Two Cardinal Functions

• Symmetric renewal: 2 stem cells → maintains pool
• Symmetric differentiation: 2 committed progenitors → depletes pool
• Asymmetric division: 1 stem + 1 progenitor → most common/balanced

Self-Renewal Regulators

Surface Markers of HSCs

Clinical use: CD34+ cells are mobilized from bone marrow into blood using G-CSF (granulocyte colony-stimulating factor) for stem cell harvest and transplant.

Developmental Biology

• Primitive hematopoiesis: begins in the yolk sac (produces mostly red cells for oxygen delivery to growing embryo)
• Definitive hematopoiesis: moves to aorto-gonad-mesonephros (AGM) region, then fetal liver and spleen, then settles permanently in the bone marrow
• Key transcription factors: Runx1 (CBFA2) is essential - it appears at the first site of definitive hematopoiesis

The HSC Niche (Microenvironment)

• Osteoblasts (lining the endosteum) - provide physical support and secrete CXCL12 (SDF-1)
• CXCR4 on HSCs binds CXCL12 on osteoblasts - this tethers cells to marrow
• Mesenchymal stromal cells
• Endothelial cells (perivascular niche)

Mobilization

• G-CSF is the standard agent for mobilizing HSCs
• Plerixafor (CXCR4 antagonist) used when G-CSF alone is insufficient
• Mobilized CD34+ cells are collected by apheresis and used for transplantation

HSC Differentiation Hierarchy

HSC
├── Common Lymphoid Progenitor (CLP)
│   ├── T cells
│   ├── B cells
│   └── NK cells
└── Common Myeloid Progenitor (CMP)
    ├── Granulocyte-Monocyte Progenitor (GMP)
    │   ├── Neutrophils, Eosinophils, Basophils
    │   └── Monocytes → Macrophages
    └── Megakaryocyte-Erythroid Progenitor (MEP)
        ├── Erythrocytes
        └── Platelets

• EPO (erythropoietin) → erythroid
• TPO (thrombopoietin) → megakaryocytic
• G-CSF → neutrophilic
• M-CSF → monocyte/macrophage
• IL-3, SCF → broad support

Excess Capacity

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CHAPTER 102 - IRON DEFICIENCY AND OTHER ANEMIAS OF DECREASED ERYTHROCYTE PRODUCTION

Normal Red Cell Production (Erythropoiesis)

• Erythropoietin (EPO) is produced by peritubular cells of the kidney in response to hypoxia
• EPO acts on BFU-E and CFU-E progenitors in marrow → drives red cell production
• Normal red cell lifespan: 120 days
• Daily iron requirement for erythropoiesis: ~20-25 mg (mostly recycled from old RBCs)

Iron Metabolism - Master Concept

• Made by the liver
• Binds ferroportin (the iron exporter on enterocytes, macrophages) → causes its internalization and degradation
• When hepcidin is high → iron is trapped in cells → less circulates
• Hepcidin is induced by: iron loading, IL-6, inflammation
• Hepcidin is suppressed by: anemia, hypoxia, erythropoiesis, iron deficiency

Stages of Iron Deficiency (in order)

1. Pre-latent - Storage iron depleted (ferritin ↓). No anemia yet.
2. Latent (Iron-depleted erythropoiesis) - Transferrin ↑, serum iron ↓, transferrin sat ↓, free erythrocyte protoporphyrin (FEP) ↑. Still no anemia.
3. Iron Deficiency Anemia - Hemoglobin ↓, MCV ↓ (microcytic), MCHC ↓ (hypochromic), peripheral smear shows microcytes, hypochromic cells, target cells, pencil cells (elliptocytes)

Causes of Iron Deficiency

• Blood loss (most common in adults): GI bleeding (ulcer, cancer, IBD, hookworm), menorrhagia
• Inadequate intake: vegetarian diet, poverty, infancy
• Malabsorption: celiac disease, H. pylori gastritis, post-gastrectomy, achlorhydria
• Increased demand: pregnancy, rapid growth in infancy/adolescence

Clinical Features

• Fatigue, pallor, weakness
• Pica (craving for non-food items like ice = pagophagia, clay = geophagia)
• Koilonychia (spoon nails)
• Angular stomatitis, glossitis
• Plummer-Vinson syndrome: iron deficiency + dysphagia + esophageal web (rare, women)

Lab Findings in Iron Deficiency vs. Other Microcytic Anemias

Ferritin is an acute-phase reactant - may be falsely normal in concurrent inflammation even with true iron deficiency.

Treatment of Iron Deficiency Anemia

• Oral iron: Ferrous sulfate 325 mg TID (provides ~65 mg elemental iron/dose)
  • Take on empty stomach for best absorption (vitamin C helps)
  • Reticulocyte response in 7-10 days; Hgb rises ~1 g/dL per week
  • Continue for 3-6 months after Hgb normalizes to replete stores
• IV iron: (ferric gluconate, iron sucrose, ferric carboxymaltose) - when oral intolerant or malabsorption
• Treat underlying cause - always find and fix the bleeding source

Anemia of Chronic Disease / Anemia of Inflammation (ACD/AI)

1. IL-6 (from inflammation) → stimulates hepcidin → iron trapping → restricted iron supply to erythroid precursors
2. Reduced EPO production and response
3. Shortened red cell survival
4. Direct inhibition of erythropoiesis by cytokines (TNF-α, IL-1)

Anemia of Chronic Kidney Disease

• Due to: inadequate EPO production (primary), iron deficiency, uremic toxin inhibition of erythropoiesis
• Treatment: Erythropoiesis-stimulating agents (ESAs) - epoetin alfa, darbepoetin alfa
• Target Hgb: 10-11 g/dL (not higher - increased CV risk)
• Always correct iron deficiency before/alongside ESA

Sideroblastic Anemia

• Ring sideroblasts (iron-laden mitochondria surrounding nucleus) on Prussian blue stain of marrow
• Causes: X-linked (ALAS2 mutation), acquired (MDS, alcohol, lead, isoniazid, chloramphenicol)
• Labs: High serum iron, high ferritin, high transferrin saturation (iron overload pattern)
• Treatment: Pyridoxine (B6) for hereditary X-linked type; treat cause for acquired

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CHAPTER 103 - HEMOGLOBINOPATHIES

Hemoglobin Structure

• HbA (96%): α₂β₂
• HbA₂ (2.5%): α₂δ₂
• HbF (1%): α₂γ₂ (fetal; has higher O₂ affinity - important for fetal survival)

• α-globin genes: chromosome 16 (2 copies per chromosome = 4 total: αα/αα)
• β-globin gene: chromosome 11 (1 copy per chromosome = 2 total)

Sickle Cell Disease (HbS Disease)

Molecular Basis

• HbS forms polymer chains (tactoids) when deoxygenated
• These distort the RBC into a sickle shape → rigid, sticky, fragile

HbS Genotypes

Pathophysiology of Sickling

• Deoxy-HbS polymerizes → rigid sickle cells
• Vaso-occlusion: sickle cells + endothelial activation (via nitric oxide depletion) + inflammation → vessel blockage → ischemia
• Hemolysis: intravascular + extravascular → chronic hemolytic anemia (Hgb 6-9 g/dL)
• Nitric oxide is depleted by cell-free hemoglobin → vasoconstriction, endothelial dysfunction

Clinical Features (Organ by Organ)

• Chronic hemolytic anemia: Hgb 6-9 g/dL, reticulocytosis
• Aplastic crisis: parvovirus B19 infects erythroid progenitors → sudden Hgb drop
• Splenic sequestration crisis (children): sudden trapping of blood in spleen → shock

• Most common manifestation
• Bone pain (ischemic bone infarcts) especially hands/feet in children (dactylitis)
• Precipitated by: cold, dehydration, hypoxia, infection, stress
• Treatment: IV fluids, analgesia (NSAIDs, opioids), O₂, identify triggers

• Fever + chest pain + pulmonary infiltrate + hypoxia
• Causes: fat embolism (from bone infarction), infection, in-situ sickling
• Treatment: O₂, antibiotics, exchange transfusion, bronchodilators
• Most common cause of death

• Occurs in ~11% of patients (children most vulnerable)
• Silent cerebral infarcts common even without symptoms
• Prevention: transcranial Doppler screening in children → if velocity >200 cm/s → chronic transfusion therapy

• Sickle nephropathy: hematuria, proteinuria, renal tubular acidosis, papillary necrosis
• End-stage renal disease

• Proliferative sickle cell retinopathy (especially HbSC)
• Retinal detachment

• Avascular necrosis (AVN) of femoral head (most common), humeral head
• Osteomyelitis - often Salmonella (unlike normal population)

• Autosplenectomy by age 5 → susceptibility to encapsulated organisms (Strep pneumoniae, H. influenzae, meningococcus)

• Functional asplenia → sepsis with encapsulated organisms
• Prevention: Penicillin prophylaxis from birth to age 5; vaccinations (pneumococcal, Hib, meningococcal)

Laboratory Findings

• Hgb: 6-9 g/dL (normocytic/normochromic with reticulocytosis)
• Peripheral smear: sickle cells, target cells, Howell-Jolly bodies (asplenia)
• Elevated bilirubin (indirect), elevated LDH, elevated reticulocyte count
• Hgb electrophoresis: HbS predominant, absent HbA (in HbSS)

Treatment

• Hydroxyurea: ↑HbF production (HbF prevents sickling) → reduces VOC, ACS, transfusion needs, mortality. First-line disease-modifying therapy.
• L-glutamine: reduces oxidative stress in sickle cells; approved by FDA
• Voxelotor: binds HbS, increases O₂ affinity → reduces sickling and hemolysis
• Crizanlizumab: anti-P-selectin antibody → reduces vaso-occlusion
• Chronic transfusion: for stroke prevention/treatment, recurrent ACS
• Allogeneic HSCT: potentially curative; best results in children with HLA-matched sibling

• Lovotibeglogene autotemcel (Lyfgenia): gene addition therapy
• Exagamglogene autotemcel (Casgevy): CRISPR-Cas9 gene editing (reactivates HbF)

• Pain crisis: IV fluids, analgesics, heat packs, O₂ if hypoxic
• ACS: Exchange transfusion + antibiotics + O₂
• Aplastic crisis: Transfusion support

Thalassemias

β-Thalassemia

• β⁰: no β-chain production
• β⁺: reduced β-chain production

• Severe anemia from 3-6 months (when HbF is normally switching off)
• Hepatosplenomegaly (extramedullary hematopoiesis)
• Skeletal deformities: "chipmunk facies" (frontal bossing, maxillary prominence from marrow expansion), hair-on-end pattern on skull X-ray
• Growth retardation, delayed puberty
• Iron overload (from transfusions + increased GI absorption): cardiomyopathy, cirrhosis, endocrinopathies (DM, hypothyroidism, hypogonadism) - leading cause of death

• Regular RBC transfusions (goal: pre-transfusion Hgb >9-10 g/dL)
• Iron chelation therapy (mandatory):
  • Deferoxamine (subcutaneous/IV infusion - older, burdensome)
  • Deferasirox (oral - preferred now)
  • Deferiprone (oral - especially good for cardiac iron)
• Allogeneic HSCT: curative; best done in childhood before organ damage
• Luspatercept (TGF-β ligand trap): approved for β-thalassemia → reduces transfusion burden in non-transfusion-dependent patients

α-Thalassemia

Key Point: Why Thalassemia Trait Looks Like IDA

• Mentzer index = MCV/RBC count
  • <13 = thalassemia (high RBC count relative to low MCV)

  • 13 = IDA (low RBC count)

• HbA₂ >3.5% on HPLC/electrophoresis = β-thalassemia trait (definitive)
• Normal ferritin in thalassemia trait

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CHAPTER 104 - MEGALOBLASTIC ANEMIAS

Core Concept

DNA Synthesis and the Role of B12/Folate

• Folate (as 5,10-methyleneTHF) is essential for converting dUMP → dTMP (thymidylate synthesis)
• Vitamin B12 is needed to regenerate THF from 5-methylTHF
• Without B12 → methylfolate trap (folate gets "trapped" as 5-methylTHF → can't be used for DNA synthesis)
• Without folate OR B12 → impaired thymidylate synthesis → impaired DNA replication

1. Methionine synthase: Homocysteine + 5-methylTHF → Methionine + THF (requires B12)
2. Methylmalonyl-CoA mutase: Methylmalonyl-CoA → Succinyl-CoA (requires B12 - not folate)

Key diagnostic point: Methylmalonic acid (MMA) is elevated in B12 deficiency but NOT in folate deficiency. Both cause elevated homocysteine.

Vitamin B12 (Cobalamin) Deficiency

Sources and Absorption

• Found only in animal products (meat, fish, dairy, eggs)
• Absorption requires: intrinsic factor (IF) (secreted by gastric parietal cells) → forms IF-B12 complex → absorbed in terminal ileum via cubam receptor

Causes

1. Pernicious anemia (most common in developed world): autoimmune destruction of parietal cells → loss of IF → malabsorption
   • Anti-IF antibodies (type I - block B12 binding; type II - prevent ileal absorption) - specific for PA
   • Anti-parietal cell antibodies (sensitive but not specific)
   • Associated with autoimmune thyroid disease, vitiligo, type 1 DM
2. Dietary deficiency: strict veganism (takes years to develop - stores last 3-5 years)
3. Gastrectomy (total or partial)
4. Malabsorption: terminal ileum disease (Crohn's), ileal resection, bacterial overgrowth (consumes B12), fish tapeworm (Diphyllobothrium latum)
5. Drugs: metformin (reduces IF-independent absorption), omeprazole (long-term)
6. Gastric bypass surgery

Clinical Features

• Macrocytic anemia (MCV often >110-115 fL)
• Hypersegmented neutrophils (>5 lobes in any neutrophil, or >4 with 5-lobe neutrophils) - EARLIEST finding on smear
• Pancytopenia in severe cases
• Megaloblasts in bone marrow

• Subacute combined degeneration (SCD) of spinal cord - the most important neurologic manifestation:
  • Dorsal columns (posterior): loss of vibration sense, proprioception, Romberg positive
  • Lateral columns (corticospinal): upper motor neuron signs, spastic weakness
  • Combined = "subacute combined"
• Peripheral neuropathy (symmetric, stocking-glove)
• Dementia, psychiatric symptoms
• Neurologic symptoms can occur WITHOUT anemia (especially if folate supplements mask the hematologic picture)

• Glossitis (smooth, beefy red tongue)
• Mild jaundice (intramedullary hemolysis)

Laboratory Diagnosis

• Serum B12 <200 pg/mL (definitive)
• ↑ MMA (methylmalonic acid) - most sensitive marker for tissue B12 deficiency
• ↑ Homocysteine
• Peripheral smear: macro-ovalocytes, hypersegmented neutrophils
• For PA: anti-IF antibodies (specific), anti-parietal cell antibodies (sensitive); Schilling test (historical)

Treatment

• B12 intramuscular injections (cyanocobalamin or hydroxocobalamin)
  • 1000 mcg IM daily for 7 days, then weekly for 4 weeks, then monthly for life (PA)
  • Oral high-dose B12 (1000-2000 mcg/day) works even without IF (passive absorption) - effective and simpler
• Neurologic improvement can take months; may be incomplete if severe

Folate Deficiency

Sources and Absorption

• Found in green leafy vegetables (spinach, broccoli), legumes, fortified grains, liver, nuts
• Absorbed in proximal small intestine (duodenum/jejunum)
• Body stores last only 3-4 months (unlike B12 which lasts 3-5 years)

Causes

1. Inadequate intake (most common): alcoholics, elderly, poverty
2. Increased demand: pregnancy, hemolytic anemia, rapid cell turnover, dialysis
3. Malabsorption: celiac disease, tropical sprue, short bowel syndrome
4. Drug-induced impaired metabolism:
   • Methotrexate: inhibits DHFR (dihydrofolate reductase) → impairs THF regeneration
   • Trimethoprim, pyrimethamine: also DHFR inhibitors
   • Phenytoin: impairs folate absorption
5. Alcohol: multifactorial (poor diet + impaired absorption + increased excretion)

Clinical Features

• Same hematologic picture as B12 deficiency (macrocytic anemia, hypersegmented neutrophils)
• No neurologic complications (key differentiator from B12)
• Glossitis present

Key Warning: Folate Supplementation Masking B12 Deficiency

Treatment

• Folic acid 1-5 mg/day PO for 4+ months
• Pregnancy: 400 mcg/day pre-conception and in first trimester → prevents neural tube defects
• High-risk pregnancies (prior NTD, antiepileptics): 4-5 mg/day

Other Causes of Macrocytic Anemia (non-megaloblastic)

• Alcohol (direct toxic effect on marrow)
• Hypothyroidism
• Liver disease
• MDS (dysplastic)
• Drugs (hydroxyurea, azathioprine, zidovudine)
• Reticulocytosis (reticulocytes are large)

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CHAPTER 105 - HEMOLYTIC ANEMIAS

Core Concept

Classification

By Location of Destruction

• Intravascular: RBC bursts within blood vessel → free Hgb in plasma
  • Signs: hemoglobinemia, hemoglobinuria (pink/red/dark urine), low/absent haptoglobin
  • Causes: transfusion reactions (ABO incompatibility), PNH, TTP/HUS, G6PD with oxidative stress, mechanical valves
• Extravascular: RBC recognized as abnormal and consumed by macrophages in spleen/liver
  • Signs: jaundice (indirect bilirubin ↑), splenomegaly, urobilinogen in urine
  • Causes: AIHA (warm), hereditary spherocytosis, hemoglobinopathies

Laboratory Signs of Hemolysis

Hereditary Spherocytosis (HS)

• Most common hereditary hemolytic anemia in Northern Europeans
• Deficiency of spectrin, ankyrin, band 3, or protein 4.2 → unstable RBC membrane → loss of surface area → spherocyte formation → trapped and destroyed in spleen
• Autosomal dominant (usually)
• Clinical: hemolytic anemia, jaundice, splenomegaly; pigment gallstones common
• Smear: spherocytes (dense, round, no central pallor)
• Osmotic fragility test: increased; EMA (eosin-5-maleimide) binding test (flow cytometry): decreased - current preferred diagnostic test
• Treatment: splenectomy (reduces hemolysis markedly); folic acid supplementation; screen for and vaccinate before splenectomy
• Aplastic crisis: parvovirus B19 → temporary cessation of erythropoiesis → severe anemia

Hereditary Elliptocytosis

• Spectrin (α or β) mutations → elliptical RBCs
• Usually mild; some variants cause moderate hemolysis
• Smear: >25% elliptocytes

G6PD Deficiency (Glucose-6-Phosphate Dehydrogenase)

• Most common enzyme deficiency - affects 400 million people worldwide
• X-linked recessive (males predominantly affected)
• G6PD catalyzes first step of pentose phosphate pathway → generates NADPH → protects against oxidative stress
• Without G6PD: oxidative stress → Hgb oxidized to methemoglobin → denatured Hgb forms Heinz bodies → membrane damage → hemolysis

Triggers of Hemolysis

• Infections (most common trigger)
• Drugs: primaquine, dapsone, rasburicase, nitrofurantoin, methylene blue
• Foods: fava beans (favism)
• Metabolic acidosis

Variants

• African variant (A-): mild; only older RBCs affected; self-limited episodes
• Mediterranean variant: more severe; can cause chronic hemolysis

Laboratory

• Heinz bodies on crystal violet stain (during episode)
• Low G6PD activity (measure weeks after episode - young reticulocytes have higher G6PD levels → false normal during/after acute episode)
• Intravascular hemolysis pattern: hemoglobinuria, low haptoglobin

Treatment: Remove trigger; supportive; transfuse if severe

Pyruvate Kinase (PK) Deficiency

• Second most common enzyme defect
• Autosomal recessive
• PK needed for glycolysis → ATP generation → RBC survival
• Chronic hemolytic anemia from birth; splenomegaly
• Smear: echinocytes (burr cells)
• Treatment: Mitapivat (PK activator) - approved 2022; splenectomy helpful

Paroxysmal Nocturnal Hemoglobinuria (PNH)

• Acquired clonal disorder of hematopoietic stem cell
• Somatic mutation in PIG-A gene → failure to synthesize GPI anchor → loss of GPI-anchored complement regulatory proteins:
  • CD55 (DAF - decay accelerating factor) - normally degrades C3 convertase
  • CD59 (protectin) - normally inhibits MAC (membrane attack complex)
• Without CD55/CD59 → uncontrolled complement activation → intravascular hemolysis

Clinical Features

• Chronic intravascular hemolysis: hemoglobinuria (especially morning, after sleep/fasting → complement activation during sleep)
• Thrombosis - major cause of death; unusual sites: hepatic vein (Budd-Chiari), mesenteric veins, cerebral veins
• Pancytopenia (often associated with aplastic anemia)
• Smooth muscle dystonia: dysphagia, abdominal pain, erectile dysfunction (due to NO depletion)
• Iron deficiency (from urinary iron loss)

Diagnosis

• Flow cytometry: deficiency of CD55 and CD59 on RBCs and granulocytes - gold standard
• Old test: Ham's test (acid lysis) and sucrose lysis - outdated

Treatment

• Eculizumab (anti-C5 monoclonal antibody): blocks complement at C5 → prevents MAC formation → dramatically reduces hemolysis, thrombosis - revolutionary treatment
• Ravulizumab: long-acting anti-C5 (every 8 weeks dosing)
• Anticoagulation for thrombosis
• Folic acid, iron supplementation
• Allogeneic HSCT: curative option

Autoimmune Hemolytic Anemia (AIHA)

Warm AIHA

• IgG antibodies react at 37°C (body temperature)
• IgG-coated RBCs → Fc receptor on splenic macrophages → extravascular hemolysis (spleen)
• Also causes spherocytes (partial phagocytosis removes membrane)
• Causes: idiopathic (50%), SLE, CLL, lymphoma, drugs (methyldopa, penicillin, cephalosporins)
• Direct Coombs (DAT) positive for IgG (and sometimes C3)
• Treatment:
  1. Prednisolone 1 mg/kg/day - first line
  2. Rituximab (anti-CD20): second-line, very effective
  3. Splenectomy: third-line
  4. Newer agents: fostamatinib (Syk inhibitor), BTK inhibitors

Cold Agglutinin Disease (CAD)

• IgM antibodies react at cold temperatures (<37°C)
• IgM binds RBCs in cold peripheral tissues → activates complement → C3b opsonization → destroyed by Kupffer cells in liver (extravascular) + some intravascular via MAC
• Antibody usually has anti-I specificity (I antigen on almost all adult RBCs)
• Clonal B cells (KMT2D mutation); NOT the MYD88 mutation of Waldenström's
• Causes: idiopathic (primary CAD), Mycoplasma pneumoniae infection, infectious mononucleosis (anti-i), lymphoma
• Clinical: acrocyanosis, Raynaud's in cold; hemolysis worsens in cold weather
• DAT positive for C3 (not IgG)
• Treatment: keep warm; rituximab ± bendamustine; sutimlimab (C1s inhibitor - FDA approved for CAD 2022)

Drug-Induced Hemolytic Anemia

1. Drug adsorption (hapten) mechanism: Drug binds RBC membrane → IgG against drug+membrane (e.g., high-dose penicillin)
2. Immune complex mechanism: Drug + antibody forms complex that deposits on RBC → complement activation (e.g., quinine)
3. True autoimmune: Drug induces autoantibody against RBC antigens (e.g., methyldopa - anti-e antigen)

Microangiopathic Hemolytic Anemia (MAHA)

• Mechanical destruction of RBCs as they pass through abnormal microvasculature
• Schistocytes (helmet cells, fragmented RBCs) on smear - KEY finding
• Causes:
  • TTP (thrombotic thrombocytopenic purpura): ADAMTS13 deficiency
  • HUS (hemolytic uremic syndrome): E. coli O157:H7 Shiga toxin
  • DIC, malignant hypertension, preeclampsia/HELLP, scleroderma crisis, prosthetic heart valves

• Treatment: plasma exchange (removes ADAMTS13 inhibitor, supplies ADAMTS13) - EMERGENCY; rituximab for acquired TTP

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CHAPTER 106 - ANEMIA DUE TO ACUTE BLOOD LOSS

Three Stages of Acute Posthemorrhagic Anemia

• Dominant feature is volume loss, not anemia
• Blood count does NOT show anemia initially (Hgb concentration maintained)
• Symptoms: tachycardia, hypotension, cold/pale skin, decreased urine output, altered consciousness
• Risk: shock, acute renal failure

• Body shifts fluid from extravascular to intravascular compartment
• Also: IV fluids given → hemodilution
• Now anemia becomes apparent on CBC
• Estimate of blood lost: if Hgb = 7 g/dL after 3 days → ~50% of blood volume lost

• Reticulocytosis develops (EPO ↑)
• Hgb recovers over weeks if no continued bleeding

Key Clinical Signs by Volume Lost

Blood Loss Location Clues

• Grey Turner sign (flank ecchymosis): retroperitoneal bleed
• Cullen sign (umbilical ecchymosis): intraperitoneal/retroperitoneal bleed
• Chest dullness to percussion: hemothorax

Treatment

• IV access × 2 large bore
• Crystalloid (saline, Ringer's) for immediate volume
• Packed RBCs (1 unit raises Hgb by ~1 g/dL) for significant anemia
• Type and crossmatch blood
• Massive transfusion protocol if >10 units needed: RBC:FFP:platelets = 1:1:1
• Find and stop the bleeding source

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CHAPTER 107 - BONE MARROW FAILURE: APLASTIC ANEMIA AND MYELODYSPLASIA

Aplastic Anemia (AA)

Definition

Pathogenesis

• Auto-reactive T cells (CD8+ cytotoxic T cells) attack hematopoietic stem cells
• Mediated by IFN-γ and TNF-α
• Can be triggered by viruses (EBV, hepatitis), drugs, radiation
• Small subset: inherited (Fanconi anemia, dyskeratosis congenita, Diamond-Blackfan)

Causes

• Idiopathic (most common after immune-mediated mechanism is accepted)
• Drugs: chloramphenicol (classic), NSAIDs, gold, carbimazole, sulfonamides
• Viral: hepatitis-associated AA (seronegative hepatitis), EBV, parvovirus
• Radiation/Chemotherapy
• PNH: ~25% of AA patients have a PNH clone; AA can evolve into PNH
• Inherited: Fanconi anemia (chromosomal fragility syndrome - test with diepoxybutane), dyskeratosis congenita (short telomeres, nail dystrophy, leukoplakia, pulmonary fibrosis)

Severity Classification

Clinical Features

• Anemia: fatigue, pallor, dyspnea
• Thrombocytopenia: bleeding, petechiae, mucosal hemorrhage
• Neutropenia: infections (bacterial, fungal)
• No splenomegaly or lymphadenopathy (distinguishes from malignant causes)

Diagnosis

• CBC: pancytopenia; normocytic anemia; reticulocytopenia (key - low reticulocytes despite anemia)
• Bone marrow biopsy: hypocellular marrow with fatty replacement (definitive)
• Rule out PNH (flow cytometry), B12/folate deficiency, viral hepatitis
• Cytogenetics: rule out MDS

Treatment

• Best for young patients (<40 years) with SAA who have an HLA-matched sibling donor
• 5-year survival >80% with matched sibling
• Conditioning: cyclophosphamide + anti-thymocyte globulin (ATG)

• Anti-thymocyte globulin (ATG) - horse ATG or rabbit ATG
• Cyclosporine (suppresses T cells)
• Eltrombopag (TPO receptor agonist) added to ATG+cyclosporine → improves response rate significantly
• Response rate with ATG+cyclosporine+eltrombopag: ~60-70%
• Supportive: transfusions, antibiotics/antifungals, G-CSF

Myelodysplastic Syndromes (MDS)

Definition

1. Ineffective hematopoiesis (cytopenias despite hypercellular marrow)
2. Dysplasia (abnormal morphology of blood cell precursors)
3. Risk of transformation to AML (progression in ~30%)

Pathogenesis

• Clonal stem cell mutations → abnormal maturation → cells destroyed in marrow (ineffective erythropoiesis) + dysplastic cells
• Common mutations: TET2, DNMT3A, ASXL1, SF3B1 (associated with ring sideroblasts), TP53 (poor prognosis)
• Triggers: prior chemotherapy (especially alkylating agents), radiation, benzene exposure

WHO 2022 Classification (Key Categories)

• MDS with low blasts (MDS-LB)
• MDS with low blasts and SF3B1 mutation (MDS-SF3B1) - ring sideroblasts, good prognosis
• MDS with increased blasts 1 (MDS-IB1): 5-9% blasts
• MDS with increased blasts 2 (MDS-IB2): 10-19% blasts (highest risk)
• MDS with 5q deletion (del5q): isolated 5q-, good prognosis, responds to lenalidomide

Clinical Features

• Symptomatic anemia (most common)
• Infections (neutropenia)
• Bleeding (thrombocytopenia)
• Rare: Sweet's syndrome (neutrophilic dermatosis)

Diagnosis

• CBC: cytopenias (one or more cell lines)
• Peripheral smear: dysplastic cells
• Bone marrow biopsy: dysplasia + % blasts (defines category)
• Cytogenetics/FISH: del5q, -7, del7q, +8, del20q, complex karyotype (worst)
• Molecular testing: mutation panel

Prognosis - IPSS-R Score

Treatment

• Anemia treatment:
  • ESAs (epoetin alfa, darbepoetin) if EPO level <500 mU/mL
  • Lenalidomide: for del5q MDS → excellent response (red cell transfusion independence in ~70%)
  • Luspatercept: for MDS-SF3B1 or ring sideroblastic MDS (FDA approved 2020)
  • Transfusions + iron chelation
• Azacitidine or decitabine (hypomethylating agents, HMAs) for higher-risk lower-risk MDS

• Azacitidine (SC or IV): first-line HMA; extends survival vs best supportive care
• Decitabine: similar HMA
• Allogeneic HSCT: only potentially curative option; for eligible patients
• Venetoclax + azacitidine: emerging combination

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CHAPTER 108 - POLYCYTHEMIA VERA AND OTHER MYELOPROLIFERATIVE NEOPLASMS

Classification of Chronic MPNs (WHO 2022)

Polycythemia Vera (PV)

Pathogenesis

• JAK2 V617F mutation in >95% of cases (Val→Phe in pseudokinase domain → constitutive JAK2 activation)
• JAK2 is the tyrosine kinase for EPO and TPO receptors → constitutive activation mimics constant growth factor stimulation → uncontrolled proliferation (especially erythroid)
• Clonal, starts in HSC

Diagnosis - WHO Criteria (2022)

1. Hgb >16.5 g/dL (M) or >16 g/dL (F), OR hematocrit >49% (M) or >48% (F), OR elevated RBC mass
2. BM biopsy: hypercellular with trilineage hyperplasia (panmyelosis) + pleomorphic mature megakaryocytes
3. JAK2 V617F or JAK2 exon 12 mutation

• Subnormal serum EPO level

Clinical Features

• Symptoms of hyperviscosity: headache, visual disturbances, dizziness, tinnitus, plethora
• Pruritus (especially after hot bath = aquagenic pruritus) - due to basophil/mast cell mediators
• Thrombosis: most common cause of death (venous and arterial)
  • Unusual sites: hepatic vein (Budd-Chiari), portal vein, mesenteric vein, cerebral veins
• Erythromelalgia: burning pain + redness of hands/feet → aspirin relieves (platelet-mediated microvascular occlusion)
• Splenomegaly (60%)
• Hypertension, gout
• Transformation: to MF (~10-15% at 10 years); to AML (<5% untreated, higher with alkylating agents)

Treatment

• Aspirin 81 mg/day (reduces thrombosis risk)
• Phlebotomy: target hematocrit <45% (men) or <42% (women) - most important for thrombosis prevention

• Hydroxyurea (first-line cytoreduction): reduces RBC/platelet mass
• Ruxolitinib (JAK1/2 inhibitor): for hydroxyurea-resistant/intolerant PV - controls Hct, reduces spleen, reduces pruritus
• Interferon-α (pegylated): safe in pregnancy, can reduce JAK2 allele burden
• Ropeginterferon alfa-2b: approved for PV (2021, US)
• Phlebotomy continues regardless of cytoreduction

Erythrocytosis Differential

• Primary: PV (EPO ↓)
• Secondary: EPO ↑ appropriately (altitude, hypoxia, COPD, sleep apnea) or inappropriately (EPO-secreting tumor: RCC, hepatoma, uterine fibroids, cerebellar hemangioblastoma)

Essential Thrombocythemia (ET)

• Platelets typically >450,000/μL (often >1 million)
• Mutations: JAK2 V617F (55%), CALR (25%), MPL (3%)
• CALR mutations → good prognosis
• Clinical: thrombosis (venous/arterial), microvascular symptoms (erythromelalgia, digital ischemia), hemorrhage (with very high counts >1.5 million - acquired vWD)
• Paradox: both thrombosis AND bleeding
• Treatment: aspirin; hydroxyurea (cytoreduction) for high-risk; anagrelide (reduces platelet production); ruxolitinib

Primary Myelofibrosis (PMF)

Pathogenesis

• Fibrosis is reactive (not the clone itself causing fibrosis): megakaryocytes release TGF-β, PDGF → fibroblast activation → collagen deposition
• Extramedullary hematopoiesis (liver, spleen) → massive splenomegaly

Clinical Features

• Massive splenomegaly (most prominent feature) → abdominal pain, early satiety, splenic infarcts
• Constitutional symptoms: fever, night sweats, weight loss (cytokine excess)
• Leukoerythroblastic smear: nucleated RBCs + myelocytes/metamyelocytes in peripheral blood
• Teardrop cells (dacrocytes): pathognomonic for PMF on smear (cells squeezed through fibrotic marrow)
• Anemia (severe in advanced disease)
• Dry tap on marrow aspiration (fibrosis); biopsy shows reticulin/collagen fibrosis

Prognosis - IPSS/DIPSS/DIPSS-Plus scoring

Treatment

• Ruxolitinib (JAK1/2 inhibitor): dramatically reduces spleen size, improves constitutional symptoms → first-line for splenomegaly/symptoms
• Fedratinib, pacritinib, momelotinib: other JAK inhibitors (momelotinib helps anemia)
• Hydroxyurea: debulking
• Allogeneic HSCT: only curative option
• Splenectomy: for massive symptomatic spleen refractory to treatment (high risk procedure)
• Anemia management: androgens, ESAs (limited), danazol, thalidomide, lenalidomide
• Transfusions + iron chelation

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CHAPTER 109 - ACUTE MYELOID LEUKEMIA (AML)

Definition

Pathogenesis - Two-Hit Model

• AML with genetic abnormalities (specific mutations/translocations define subtypes)
• AML with myelodysplasia-related changes
• Therapy-related AML (t-AML)
• AML, not otherwise specified (NOS)

Key Genetic Subtypes and Their Significance

Acute Promyelocytic Leukemia (APL) - M3 - MUST KNOW

• t(15;17): PML gene fused to RARα gene → PML-RARα fusion → blocks myeloid differentiation at promyelocyte stage
• Promyelocytes accumulate → release granules → DIC (disseminated intravascular coagulation) - most dangerous feature
• High-risk of fatal bleeding if not treated immediately
• Clinical: bleeding/bruising disproportionate to cytopenias; Auer rods (faggot cells in APL)
• Treatment:
  • ATRA (all-trans retinoic acid) + Arsenic trioxide (ATO): the gold standard
  • ATRA activates differentiation of the PML-RARα cells → they mature and die normally
  • This combination achieves cure in >90% of cases
  • Start ATRA immediately upon suspicion (even before molecular confirmation)
  • ATRA differentiation syndrome: fever, weight gain, pulmonary infiltrates, renal failure from differentiating cells → treat with dexamethasone

Clinical Features of AML

• Anemia: fatigue, pallor
• Thrombocytopenia: bleeding, petechiae
• Neutropenia: fever, infections (biggest threat to life)
• Leukostasis (blast count >100,000): slugging of blasts in microvasculature → cerebral/pulmonary hemorrhage/infarction → emergency
• Gingival hypertrophy (AML-M5 monocytic → lysozyme secretion + infiltration)
• Splenomegaly (mild)
• Chloroma/granulocytic sarcoma (extramedullary deposits of blasts)

Diagnosis

• CBC: usually anemia + thrombocytopenia; WBC variable (may be high, normal, or low)
• Peripheral smear: blasts; Auer rods (pathognomonic for AML)
• Bone marrow biopsy: ≥20% blasts
• Flow cytometry: immunophenotype (CD33, CD13, CD117 - myeloid markers)
• Cytogenetics + molecular panel (FLT3, NPM1, IDH1/2, TP53, etc.)
• Coagulation: PT, PTT, fibrinogen, D-dimer (for DIC in APL)

Treatment

Induction (7+3 regimen - standard)

• Cytarabine (Ara-C) 100-200 mg/m² continuous infusion × 7 days
• Daunorubicin (or idarubicin) × 3 days ("3+7")
• Goal: achieve complete remission (CR = <5% blasts in marrow)

Targeted additions to induction:

• Midostaurin + 7+3 for FLT3-mutated AML
• Gemtuzumab ozogamicin (GO) added for favorable-risk AML (CD33+)
• ATRA + ATO for APL (instead of 7+3)

Post-remission (consolidation):

• High-dose cytarabine (HiDAC): for favorable-risk (t(8;21), inv(16))
• Allogeneic HSCT: for intermediate/poor-risk AML in CR1
• FLT3-targeted maintenance: midostaurin or gilteritinib
• Venetoclax + azacitidine or low-dose cytarabine: for older/unfit patients

Relapsed/Refractory AML:

• Gilteritinib (FLT3+ relapsed)
• Enasidenib/ivosidenib (IDH2+/IDH1+)
• CPX-351 (liposomal daunorubicin + cytarabine) for secondary AML
• Glasdegib (Hedgehog inhibitor) + LDAC for unfit

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CHAPTER 110 - CHRONIC MYELOID LEUKEMIA (CML)

The Paradigm of Targeted Therapy

Pathogenesis

• ABL1 gene (chr 9) fuses with BCR gene (chr 22)
• Creates BCR-ABL1 fusion protein
• BCR-ABL1 is a constitutively active tyrosine kinase → uncontrolled myeloid proliferation
• Present in >95% of CML patients
• BCR-ABL1 drives proliferation via RAS, PI3K/AKT, JAK-STAT, and MYC pathways

• Major breakpoint (M-BCR) → p210 BCR-ABL1 (typical CML)
• Minor breakpoint (m-BCR) → p190 (Ph+ ALL, some CML)
• μ-BCR → p230 (chronic neutrophilic leukemia)

Clinical Phases

Clinical Features (Chronic Phase)

• Often asymptomatic, found incidentally on CBC
• Leukocytosis: WBC often 50,000-500,000/μL (neutrophils, bands, metamyelocytes, eosinophils, basophils - full myeloid spectrum)
• Basophilia (characteristic)
• Massive splenomegaly (most prominent physical finding)
• Fatigue, weight loss, night sweats (constitutional)
• Leukostasis if WBC very high

Diagnosis

• CBC: markedly elevated WBC with full myeloid spectrum + basophilia + eosinophilia
• Peripheral smear: myelocytes, metamyelocytes, basophils, eosinophils
• LAP score low (leukocyte alkaline phosphatase) - distinguishes from leukemoid reaction (LAP high)
• BM biopsy: hypercellular, myeloid hyperplasia
• BCR-ABL1 by RT-PCR or FISH: defines diagnosis (quantitative PCR used for monitoring)
• Cytogenetics: t(9;22) in >95%
• Vitamin B12 markedly elevated (WBCs produce transcobalamin)

Treatment - Tyrosine Kinase Inhibitors (TKIs) - Revolution in Medicine

First-Generation:

• Imatinib (Gleevec): first BCR-ABL1 TKI; changed CML from fatal to chronic manageable disease; 5-year survival >85%

Second-Generation (more potent, used first-line):

• Dasatinib: more potent; crosses blood-brain barrier
• Nilotinib: more potent; watch for hyperglycemia, prolonged QTc
• Bosutinib: good for imatinib failure

Third-Generation:

• Ponatinib: active against T315I mutation (the "gatekeeper" mutation resistant to all others)
• Asciminib (STAMP inhibitor): binds myristoyl pocket of ABL → different mechanism; active against T315I

Response Milestones

Resistance

• Most common: T315I mutation in BCR-ABL1 kinase domain (resistant to imatinib, dasatinib, nilotinib, bosutinib) → use ponatinib or asciminib
• Other mutations: Y253H, E255K, etc.

Allogeneic HSCT

• Previously the only cure; now used mainly for blast crisis or TKI failure/intolerance
• Still potentially curative in these settings

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CHAPTER 111 - ACUTE LYMPHOBLASTIC LEUKEMIA (ALL)

Overview

• Most common cancer in children (peak 2-5 years)
• Second peak in adults >60 years
• B-cell ALL (85%): CD19+, CD10+, TdT+
• T-cell ALL (15%): CD3+, CD7+, TdT+; mediastinal mass common (young males)

Key Genetic Subtypes

Clinical Features

• Bone pain (leukemic infiltration of marrow → classic in children, limping, refusing to walk)
• Hepatosplenomegaly, lymphadenopathy
• CNS involvement: meningism, cranial nerve palsies (meningeal leukemia)
• Mediastinal mass → SVC syndrome (T-cell ALL)
• Testicular involvement in boys
• Bleeding, infections, anemia

Diagnosis

• Blasts on smear: lymphoblasts (fine chromatin, scant cytoplasm, no Auer rods)
• BM biopsy: ≥20% lymphoblasts
• Immunophenotype: B-ALL (CD19, CD10, CD22, TdT) vs T-ALL (CD3, CD7, TdT)
• Cytogenetics + FISH + molecular (BCR-ABL1, KMT2A, ETV6-RUNX1)
• CSF examination (meningeal leukemia)

Treatment

Children (excellent results):

• Multi-agent chemotherapy protocols (COG protocols)
• Induction (~4 weeks): vincristine + prednisone + asparaginase ± daunorubicin → 95% CR
• CNS prophylaxis: intrathecal methotrexate (replaced cranial radiation)
• Consolidation + maintenance (2-3 years)
• 5-year survival in children: >90%

Adults (more challenging):

• Similar regimens but poorer outcomes (overall survival ~40-50%)
• Ph+ ALL: add TKI (dasatinib, ponatinib) to chemotherapy → dramatically improves outcome
  • Blinatumomab + ponatinib (without chemo): emerging chemotherapy-free regimen
• Allogeneic HSCT for high-risk adults in CR1

Relapsed/Refractory:

• Blinatumomab (BiTE - bispecific T-cell engager - CD19×CD3): bridges T cells to leukemia cells
• Inotuzumab ozogamicin (anti-CD22 antibody-drug conjugate)
• CAR-T cells (tisagenlecleucel = Kymriah): CD19-directed; FDA approved; remarkable responses in relapsed pediatric ALL

CNS Disease

• Intrathecal chemotherapy (methotrexate ± cytarabine ± hydrocortisone)
• CNS prophylaxis given to all patients (high risk of CNS relapse)

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CHAPTER 112 - CHRONIC LYMPHOCYTIC LEUKEMIA (CLL)

Overview

• Most common leukemia in adults in Western world
• Median age at diagnosis: 70 years
• Monoclonal proliferation of mature-appearing B lymphocytes (small round, mature B cells)
• CD5+ (key - normally a T cell marker, aberrantly expressed in CLL)

Diagnostic Criteria

• Peripheral blood B-lymphocyte count ≥5000/μL for ≥3 months
• Characteristic immunophenotype: CD5+, CD19+, CD23+, dim surface immunoglobulin (sIg), dim CD20

Monoclonal B-cell lymphocytosis (MBL): clonal B cells <5000/μL; not CLL; risk of progression to CLL ~1%/year

Pathogenesis

• B cells arrest at mature naive B-cell stage, accumulate (fail to undergo apoptosis)
• Key mutations: del13q14 (most common, best prognosis), del11q23 (ATM, poor), del17p (TP53, worst), +12
• IGHV mutation status: mutated IGHV (came from germinal center) = favorable; unmutated IGHV = aggressive

Staging

Clinical Features

• Majority asymptomatic at diagnosis (found on routine CBC)
• Lymphadenopathy (most common physical finding)
• Splenomegaly, hepatomegaly
• Hypogammaglobulinemia → recurrent infections (especially encapsulated bacteria)
• Autoimmune complications:
  • AIHA (autoimmune hemolytic anemia) - warm-antibody type - in 10-25%
  • ITP (immune thrombocytopenic purpura)
• Richter transformation: CLL → diffuse large B-cell lymphoma (DLBCL) or Hodgkin lymphoma (aggressive; poor prognosis; 1-5%/year)

Treatment

• Progressive cytopenias
• Symptomatic splenomegaly/lymphadenopathy
• B symptoms
• Autoimmune complications not responding to treatment
• Rapidly progressive disease (lymphocyte doubling time <6 months)

1. BTK inhibitors (Bruton's Tyrosine Kinase inhibitors):
   • Ibrutinib: first BTK inhibitor; excellent results; continuous therapy; some CV toxicity (AFib, hypertension)
   • Acalabrutinib: more selective, fewer off-target effects
   • Zanubrutinib: most selective BTK inhibitor; approved 2023 for CLL
   • These have largely replaced chemotherapy as first-line
2. BCL-2 inhibitors:
   • Venetoclax: inhibits BCL-2 (anti-apoptotic protein highly expressed in CLL) → induces apoptosis
   • Used as time-limited therapy (12-24 months)
   • Combined with obinutuzumab (anti-CD20): excellent deep responses, MRD negativity
3. Anti-CD20 antibodies:
   • Rituximab: anti-CD20 (chimeric)
   • Obinutuzumab (GA101): more potent anti-CD20, better in CLL
   • Combined with chemotherapy (FCR = fludarabine + cyclophosphamide + rituximab) - historical standard, still used in young fit patients with mutated IGHV
4. del17p/TP53 mutations: chemoimmunotherapy does NOT work; use BTK inhibitors or venetoclax-based
5. Allogeneic HSCT: for very high-risk refractory disease

Complications to Know

• Hypogammaglobulinemia → IVIG replacement if recurrent infections
• AIHA/ITP → steroids first, then rituximab
• Richter transformation → aggressive chemo + HSCT

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CHAPTER 113 - NON-HODGKIN LYMPHOMA (NHL)

Classification Principle

• B-cell NHLs (85%): from B cells at various stages
• T/NK-cell NHLs (15%): from T cells

Major B-Cell NHLs

Diffuse Large B-Cell Lymphoma (DLBCL)

• Most common NHL (30-35% of all NHL)
• Aggressive but potentially curable
• Two major subtypes by gene expression:
  • GCB (germinal center B-cell): BCL6 translocations, favorable prognosis
  • ABC (activated B-cell): BCL2, NF-κB activation; poorer prognosis
• Important subtypes: MYC + BCL2 and/or BCL6 translocations = Double/Triple Hit Lymphoma (very aggressive, treat with DA-EPOCH-R)
• Clinical: rapidly enlarging lymph node mass, B symptoms (fever, night sweats, >10% weight loss), extranodal involvement common
• Diagnosis: lymph node biopsy; CD20+, CD19+; Ki67 high (>70%)
• Treatment: R-CHOP (rituximab + cyclophosphamide + doxorubicin + vincristine + prednisone) × 6 cycles → cure in ~60-70%
• Relapsed: salvage chemo (R-ICE, R-DHAP) → autologous HSCT if responding
• CAR-T (axicabtagene ciloleucel, tisagenlecleucel, lisocabtagene maraleucel): approved for relapsed/refractory DLBCL after ≥2 prior lines
• Polatuzumab vedotin + R-CHP (pola-R-CHP): now preferred in some settings

Follicular Lymphoma (FL)

• Most common indolent NHL
• t(14;18): BCL2 gene juxtaposed to IgH promoter → overexpression of BCL2 (anti-apoptotic protein) → cell survival
• Clinical: painless waxing/waning lymphadenopathy; bone marrow often involved; splenomegaly
• Natural history: median survival >10 years; can transform to DLBCL (~30%)
• Grades 1-3A: indolent; Grade 3B: treated as aggressive
• FLIPI score for prognosis
• Treatment:
  • Asymptomatic/low-burden: watch and wait
  • Symptomatic: rituximab + bendamustine (R-B) or R-CHOP; obinutuzumab + chemotherapy
  • Maintenance rituximab after response
  • Relapsed: lenalidomide + rituximab (R²); PI3K inhibitors (idelalisib, copanlisib); CAR-T (axicabtagene for FL)
  • Allogeneic HSCT for transformed/multiply relapsed

Mantle Cell Lymphoma (MCL)

• t(11;14): cyclin D1 overexpression (pathognomonic)
• CD5+ (like CLL), but CD23- (unlike CLL)
• Intermediate/aggressive behavior; historically poor prognosis
• Tends to involve GI tract (lymphomatous polyposis), bone marrow, blood
• Treatment: R-CHOP or R-hyperCVAD alternating with MTX-Ara-C followed by autologous HSCT
• BTK inhibitors (ibrutinib, acalabrutinib, zanubrutinib) for relapsed/refractory - highly effective
• Venetoclax also active

Marginal Zone Lymphoma (MZL)

1. Extranodal MZL (MALT lymphoma): most common
   • Gastric MALT: associated with H. pylori infection → eradication of H. pylori alone cures 70-80% of early gastric MALT!
   • Other sites: lung, thyroid (Hashimoto's), salivary gland (Sjögren's), conjunctiva
   • Associated with chronic immune stimulation
2. Splenic MZL: splenomegaly; associated with hepatitis C virus
3. Nodal MZL: lymph node based

Burkitt Lymphoma

• Fastest growing tumor (doubling time ~24-48 hours)
• t(8;14): MYC translocation (IgH locus) → MYC overexpression → explosive proliferation
• Three variants: endemic (African; jaw mass; EBV-associated), sporadic (Western; abdominal mass), immunodeficiency-associated (HIV)
• Smear: medium-sized blast cells with starry sky appearance on histology (macrophages eating dead cells)
• Treatment: intensive, short-duration regimens (CODOX-M/IVAC, HyperCVAD, DA-EPOCH-R) → excellent cure rates in young patients (~80%)
• Tumor lysis syndrome (TLS) is a major risk → aggressive prophylaxis with allopurinol/rasburicase and IV fluids mandatory

Major T-Cell NHLs

Peripheral T-Cell Lymphoma (PTCL, NOS)

• Aggressive; poor prognosis; CD4+ mature T cells
• Treatment: CHOP-based ± brentuximab if CD30+

Anaplastic Large Cell Lymphoma (ALCL)

• ALK+ (t(2;5), NPM-ALK): young patients, excellent prognosis (~80% cure with CHOP)
• ALK-: older, worse prognosis
• CD30+: highly expressed → excellent target for brentuximab vedotin (BV) (anti-CD30 antibody-drug conjugate)
• BV + CHP (instead of CHOP): now preferred first-line for ALCL

Adult T-Cell Leukemia/Lymphoma (ATLL)

• Caused by HTLV-1 virus
• Endemic in Japan, Caribbean, Africa
• Hypercalcemia, skin lesions, lymphadenopathy, clover-leaf cells (flower cells)
• Aggressive; poor prognosis

Cutaneous T-Cell Lymphoma (CTCL)

• Mycosis fungoides: most common CTCL; CD4+ T cells infiltrate skin
  • Stages: patch → plaque → tumor → erythroderma
  • Sézary syndrome: erythroderma + circulating Sézary cells (abnormal CD4+ T cells with cerebriform nucleus)
• Treatment (skin-directed early): PUVA, topical nitrogen mustard; systemic: bexarotene, vorinostat (HDAC inhibitor), mogamulizumab (anti-CCR4)

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CHAPTER 114 - HODGKIN LYMPHOMA

Epidemiology

• Bimodal age distribution: young adults (15-35 years) + elderly (>55 years)
• Associated with EBV (especially mixed cellularity type; immunodeficiency-related HL)
• Excellent prognosis - among most curable cancers

Pathognomonic Feature: Reed-Sternberg (RS) Cell

• Large binucleated cells with prominent nucleoli ("owl-eye appearance")
• CD30+ (CD15+ in classical HL)
• Derived from germinal center B cells (despite B-cell origin, lost B-cell markers)
• RS cells are a minority (~1%) - surrounded by reactive inflammatory cells (majority of the tumor mass)

Classification

Classical Hodgkin Lymphoma (cHL) - 95%

Nodular Lymphocyte-Predominant HL (NLPHL) - 5%

• Lymphocyte-predominant (LP) cells / "popcorn cells": large cells with folded nucleus
• CD20+, CD30-, CD15- (different from cHL!)
• Indolent; late relapses; excellent prognosis
• Treatment: rituximab (because CD20+) effective

Clinical Features

• Painless cervical/supraclavicular lymphadenopathy (most common presentation)
• Mediastinal involvement (40%): cough, dyspnea; large mediastinal mass may cause SVC syndrome
• B symptoms (20-30%): fever >38°C, drenching night sweats, >10% weight loss
• Pel-Ebstein fever: periodic fever (pathognomonic but rare)
• Alcohol-induced pain in involved lymph nodes (classic but rare)
• Splenomegaly, hepatomegaly in advanced disease

Staging - Ann Arbor/Lugano

Treatment

Early-Stage (Stage I-II, favorable):

• ABVD × 2-4 cycles (doxorubicin + bleomycin + vinblastine + dacarbazine) + involved-site radiotherapy (ISRT)
• PET after 2 cycles (interim PET): if PET negative → can de-escalate; if positive → escalate

Advanced Stage (III-IV) or Unfavorable:

• ABVD × 6 cycles or
• BV-AVD (brentuximab vedotin + doxorubicin + vinblastine + dacarbazine): superior to ABVD for advanced HL; replaces bleomycin → reduces pulmonary toxicity
• PET-adapted treatment

Relapsed/Refractory (Salvage):

• Brentuximab vedotin (BV) + salvage chemo → autologous HSCT (if chemosensitive)
• Checkpoint inhibitors: nivolumab (anti-PD-1) and pembrolizumab - very effective in relapsed HL (HL overexpresses PD-L1 due to amplification of 9p24.1)
  • HL is one of the most PD-1 responsive tumors
• BV + nivolumab (after failure): excellent response rates

Toxicities to Monitor:

• Bleomycin: pulmonary fibrosis (check PFTs; stop if decline)
• Anthracyclines (doxorubicin): cardiomyopathy
• Radiation: cardiovascular disease, secondary malignancies, hypothyroidism
• Secondary malignancies: most important late complication (breast cancer in women radiated to mediastinum, lung cancer, MDS/AML)
• Infertility: discuss sperm/egg banking before treatment

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CHAPTER 115 - LESS COMMON LYMPHOID AND MYELOID MALIGNANCIES

Key Entities

Hairy Cell Leukemia (HCL)

• Rare B-cell neoplasm; middle-aged men
• BRAF V600E mutation: present in >95% of classic HCL (pathognomonic)
• Smear: cells with hair-like projections (cytoplasmic projections)
• TRAP (tartrate-resistant acid phosphatase) stain positive
• Pancytopenia + dry tap (marrow fibrosis) + massive splenomegaly (no lymphadenopathy)
• Treatment: Cladribine (2-CdA) or pentostatin → durable complete remissions in ~90%
• Relapsed: BRAF inhibitors (vemurafenib), rituximab

Large Granular Lymphocyte (LGL) Leukemia

• CD8+ T-cell (or NK-cell) clonal proliferation
• STAT3 mutations (most common)
• Neutropenia (most prominent) + anemia + splenomegaly
• Associated with rheumatoid arthritis (Felty's syndrome overlap)
• Indolent course; treatment for cytopenias: methotrexate, cyclosporine, cyclophosphamide

Waldenström Macroglobulinemia (WM)

• Lymphoplasmacytic lymphoma producing monoclonal IgM
• MYD88 L265P mutation: present in >90% → critical for diagnosis
• Clinical: hyperviscosity syndrome (IgM is large pentamer, markedly raises serum viscosity) → visual disturbances, headache, stroke
• Cold agglutinin disease (anti-I IgM) → hemolytic anemia
• Peripheral neuropathy (IgM binds myelin-associated glycoprotein, MAG)
• Cryoglobulinemia
• Treatment: ibrutinib (BTK inhibitor): very effective; rituximab + bendamustine or cyclophosphamide; plasmapheresis for hyperviscosity crisis

Chronic Neutrophilic Leukemia (CNL)

• CSF3R mutations
• Sustained neutrophilia >25,000/μL without other explanation
• Treatment: ruxolitinib (JAK inhibitor) based on biology

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CHAPTER 116 - PLASMA CELL DISORDERS

Overview

• MGUS → Smoldering MM → Multiple Myeloma
• Waldenström macroglobulinemia (IgM)
• Heavy chain diseases
• Primary amyloidosis (AL amyloidosis)

MGUS (Monoclonal Gammopathy of Undetermined Significance)

• M-protein <3 g/dL + plasma cells in marrow <10% + no end-organ damage (CRAB)
• Prevalence: 3% of adults >50 years; 5% >70 years
• Risk of progression to MM: 1% per year
• Mayo Clinic risk factors for progression: M-protein >1.5 g/dL, non-IgG isotype, abnormal FLC (free light chain) ratio
• Management: observation only; no treatment

Multiple Myeloma (MM)

Diagnostic Criteria (IMWG 2014)

• CRAB criteria:
  • Calcium >11 mg/dL (hypercalcemia)
  • Renal: creatinine >2 mg/dL or CrCl <40 mL/min
  • Anemia: Hgb <10 g/dL
  • Bone lesions: ≥1 osteolytic lesion on imaging
• SLiM criteria (biomarkers):
  • S: ≥60% plasma cells in BM
  • Li: involved FLC ratio ≥100
  • M: >1 focal lesion on MRI

Pathogenesis

• Plasma cells produce M-protein (most common IgG 50%, IgA 25%, light chain only 20%)
• Bence Jones proteins: free light chains in urine (not detected by urine protein dipstick - use urine protein electrophoresis)
• Plasma cells produce RANKL → osteoclast activation → bone destruction (lytic lesions, pathological fractures, hypercalcemia)
• IL-6 from marrow stromal cells supports MM cell growth
• Bone marrow suppression → anemia, immunosuppression

Clinical Features (CRAB)

• Lytic lesions (punched-out lesions on X-ray), NO osteoblastic activity → bone scan is insensitive (use PET-CT or whole-body low-dose CT)
• Pathological fractures: vertebral compression (back pain + height loss), long bone fractures
• Back pain is the most common presenting symptom

• Light chain cast nephropathy (myeloma kidney): free light chains precipitate in tubules → tubular obstruction
• Hypercalcemia-induced renal vasoconstriction
• Amyloid deposition (AL)
• NSAIDs worsens

Staging

• Stage I: β2M <3.5 + albumin ≥3.5 + normal LDH + no high-risk cytogenetics → best prognosis
• Stage III: β2M ≥5.5 + high LDH or high-risk cytogenetics → worst

Treatment - Modern Era (Dramatically Improved Outcomes)

1. Induction (4-6 cycles): VRd (bortezomib + lenalidomide + dexamethasone) or daratumumab + VRd (Dara-VRd) - current standard
2. Autologous HSCT (high-dose melphalan conditioning): deepens response
3. Maintenance: lenalidomide until progression

• Dara-VRd or VRd (dose-reduced); continuous therapy

Smoldering Multiple Myeloma (SMM)

• M-protein ≥3 g/dL and/or ≥10% plasma cells in BM but NO CRAB criteria
• Risk of progression ~10%/year initially (higher risk than MGUS)
• High-risk SMM: consider treatment (lenalidomide now approved to delay progression)

Heavy Chain Diseases

• Overproduction of heavy chain fragments without light chains
• α-HCD (intestinal): Middle Eastern, diarrhea, malabsorption → H. pylori association; can regress with antibiotics
• γ-HCD (Franklin's disease): rare; lymphoma-like
• μ-HCD: CLL-like

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CHAPTER 117 - AMYLOIDOSIS

Definition

Types of Amyloidosis

AL Amyloidosis (Primary - Most Clinically Important)

Pathogenesis

• Clonal plasma cells (or B cells in lymphoma) produce misfolded light chains → aggregate as amyloid fibrils → deposit in tissues
• λ light chains more amyloidogenic than κ

Clinical Features (Multi-system)

• Heart: restrictive cardiomyopathy (most common cause of death); low voltage on ECG with thick walls on echo (classic); granular sparkling appearance on echo; diastolic dysfunction; arrhythmias
• Kidney: nephrotic syndrome (massive proteinuria) → edema; renal failure
• Liver: hepatomegaly; elevated ALP; rarely jaundice
• Nervous system: peripheral neuropathy (painful); autonomic neuropathy (orthostatic hypotension, impotence, GI dysmotility)
• Tongue macroglossia (pathognomonic when present)
• Periorbital ecchymosis ("raccoon eyes") - after minor trauma; vessel fragility
• Carpal tunnel syndrome (bilateral, early sign)
• Shoulder pad sign (soft tissue infiltration of shoulder girdle)
• Factor X deficiency (adsorption to amyloid fibrils) → bleeding diathesis

Diagnosis

• Tissue biopsy required for definitive diagnosis
  • Abdominal fat pad aspirate: easiest, least invasive (80% sensitivity)
  • Rectal biopsy
  • Bone marrow biopsy (if MM suspected)
  • Organ biopsy (kidney, heart, liver) for definitive diagnosis
• Congo red staining → apple-green birefringence
• Immunohistochemistry or mass spectrometry (laser microdissection): identifies fibril type (essential for typing AL vs ATTR vs AA)
• Serum/urine protein electrophoresis + FLC ratio: for M-protein
• Echocardiography + cardiac MRI (late gadolinium enhancement in amyloid pattern)
• 99mTc-PYP (pyrophosphate) scan: highly sensitive for ATTR; now used for non-invasive diagnosis of cardiac ATTR

Treatment of AL Amyloidosis

• Treat the underlying plasma cell clone:
  • Autologous HSCT (high-dose melphalan): for eligible patients → best outcomes
  • CyBorD (cyclophosphamide + bortezomib + dexamethasone): standard induction/for ineligible
  • Daratumumab + CyBorD: improves responses (Andromeda trial)
• Supportive:
  • Heart failure: diuretics (caution - small ventricle); avoid digoxin, calcium channel blockers, ACE inhibitors (can worsen hypotension)
  • Dialysis for end-stage renal disease

ATTR Amyloidosis (Transthyretin Amyloidosis)

• Hereditary ATTR (hATTR): mutations in TTR gene (>120 mutations known; Val30Met most common in families)
• Wild-type ATTR (wtATTR): senile systemic amyloidosis; elderly men (>60 years); cardiomyopathy; no TTR mutation

• Tafamidis (TTR stabilizer): binds TTR tetramers → prevents fibril formation → reduces cardiac mortality in wtATTR and hATTR-cardiac
• Patisiran (RNAi): silences TTR gene in liver; approved for hATTR polyneuropathy and cardiomyopathy
• Inotersen (antisense oligonucleotide): also silences TTR; approved for hATTR polyneuropathy
• Vutrisiran (improved RNAi, quarterly dosing)
• Eplontersen: approved for hATTR polyneuropathy 2023

AA Amyloidosis

• Occurs with chronic inflammatory diseases: RA, IBD, chronic infections (osteomyelitis, TB, bronchiectasis), periodic fever syndromes (FMF)
• Kidney predominant (unlike AL which affects heart and kidney)
• Treatment: treat the underlying inflammatory disease (reduces SAA → amyloid may partially regress)
• Colchicine: for FMF-associated AA
• IL-1 inhibitors (anakinra, canakinumab) for periodic fever syndromes

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CHAPTER 118 - TRANSFUSION THERAPY AND BIOLOGY

Blood Groups and Compatibility

ABO System

• Most important blood group system
• A antigens, B antigens on RBCs
• Naturally occurring antibodies (anti-A IgM, anti-B IgM) form without prior exposure
• ABO incompatible transfusion = most dangerous reaction (acute hemolytic transfusion reaction with potentially fatal intravascular hemolysis)
• Group O = universal RBC donor (no ABO antigens)
• Group AB = universal plasma donor (no ABO antibodies)

Rh System

• Rh(D) antigen: most immunogenic; if Rh- patient receives Rh+ blood → forms anti-D IgG → hemolytic disease of fetus/newborn (HDFN) in future Rh+ pregnancies
• Anti-D prophylaxis: Rh immune globulin (RhoGAM) given to Rh- pregnant women to prevent sensitization

Blood Components

Packed Red Blood Cells (PRBCs)

• 1 unit raises Hgb by ~1 g/dL and Hct by ~3%
• Stored at 4°C, up to 42 days (with additive solution)
• Transfusion thresholds:
  • Liberal: Hgb <10 g/dL (symptomatic anemia, cardiac disease)
  • Restrictive: Hgb <7 g/dL (most stable non-cardiac inpatients) ← TRICC trial showed equivalent outcomes with restrictive threshold → use restrictive strategy

Platelets

• 1 unit raises platelet count by ~5,000-10,000/μL
• Stored at 20-24°C with continuous agitation, up to 5-7 days
• Transfusion threshold: <10,000/μL (stable, no bleeding); <20,000/μL with risk factors; <50,000/μL pre-procedure; <100,000/μL major surgery or CNS procedure
• ABO-compatible preferred but not mandatory

Fresh Frozen Plasma (FFP)

• Contains all coagulation factors
• Stored frozen up to 1 year; thaw before use
• Indications: coagulopathy with bleeding (PT/PTT >1.5x normal), warfarin reversal (urgent), TTP (plasma exchange), massive transfusion (1:1:1 ratio)
• Dose: 10-15 mL/kg

Cryoprecipitate

• Prepared from FFP; contains: fibrinogen, Factor VIII, vWF, Factor XIII, fibronectin
• Indication: fibrinogen <100-150 mg/dL, hemophilia A (no factor concentrate available), vWD
• Dose: 1 unit raises fibrinogen by ~7-10 mg/dL

Granulocyte Transfusions

• For severe, prolonged neutropenia with life-threatening infection not responding to antibiotics
• Rarely used due to short shelf-life and reactions

Modifications to Blood Products

Transfusion Reactions

Massive Transfusion

• 10 units PRBCs in 24 hours

• Protocol: 1:1:1 ratio (PRBC:FFP:platelets) to prevent dilutional coagulopathy
• TXA (tranexamic acid): reduces mortality in trauma bleeding if given within 3 hours
• Calcium supplementation (citrate in blood products chelates calcium)
• Monitor: ionized calcium, coagulation, temperature, acid-base

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CHAPTER 119 - HEMATOPOIETIC CELL TRANSPLANTATION (HCT)

Overview

1. Autologous HCT (auto): patient's own stem cells collected, stored, then reinfused after high-dose chemotherapy
2. Allogeneic HCT (allo): donor stem cells from another person

Sources of Stem Cells

• Bone marrow: original source; collected under anesthesia via posterior iliac crests
• Peripheral blood stem cells (PBSCs): mobilized with G-CSF (± plerixafor) → collected by apheresis; most common current source; faster engraftment
• Umbilical cord blood (UCB): collected at birth; lower cell dose → slower engraftment; more tolerance for HLA mismatch; less GVHD; good for patients without matched donors

Indications

Autologous HCT

• Multiple myeloma (consolidation after induction) - most common indication
• Relapsed/refractory DLBCL (chemosensitive)
• Hodgkin lymphoma (2nd line)
• T-cell lymphoma
• Relapsed/refractory ALL in selected cases
• NOT curative of underlying disease - uses patient's own (potentially contaminated) cells

Allogeneic HCT

• AML (intermediate/high-risk, in CR1 or CR2)
• ALL (high-risk/relapsed)
• MDS (higher-risk)
• CML (blast crisis, TKI failure)
• Aplastic anemia (SAA - best option for young with matched sibling)
• Hemoglobinopathies (sickle cell, β-thalassemia major) - curative
• Inherited marrow failure syndromes (Fanconi, Diamond-Blackfan)
• Primary immunodeficiencies (SCID)

Conditioning Regimens

HLA Matching

• Critical for allogeneic transplant compatibility
• Main HLA genes: HLA-A, -B, -C (class I) and HLA-DR, -DQ, -DP (class II)
• Matched sibling: 1/4 chance for each sibling; ~25% of patients have one
• Matched unrelated donor (MUD): registries (NMDP/Be the Match); 10/10 HLA-matched
• Haploidentical: half-matched (parent, child, sibling) - increasingly used with post-transplant cyclophosphamide (PTCy)
• Cord blood: greater HLA mismatch tolerated

Engraftment

• Neutrophil engraftment: ANC >500/μL for 3 consecutive days
  • Peripheral blood: ~day 10-14
  • Bone marrow: ~day 14-21
  • Cord blood: ~day 21-28
• Platelet engraftment: usually lags by 1-2 weeks

Graft-Versus-Host Disease (GVHD) - Most Important Complication

Acute GVHD (within 100 days)

• Grade I: mild skin only
• Grade II: moderate; skin + gut/liver
• Grade III: severe; significant gut/liver
• Grade IV: life-threatening; severe involvement

• Prophylaxis: calcineurin inhibitors (cyclosporine or tacrolimus) + methotrexate (for bone marrow donors) or mycophenolate (for PBSC donors)
• First-line acute GVHD: methylprednisolone 2 mg/kg/day
• Steroid-refractory aGVHD: ruxolitinib (JAK1/2 inhibitor) - FDA approved; dramatically improved outcomes for steroid-refractory aGVHD

Chronic GVHD (>3 months; can overlap with acute)

• Can affect any organ; most commonly: skin (lichen planus-like, scleroderma-like), eyes (dry eyes, sicca syndrome), mouth (lichen planus), lung (bronchiolitis obliterans), liver, joints/fascia
• Resembles autoimmune disease
• Treatment: steroids ± additional immunosuppression; ibrutinib approved for refractory cGVHD; ruxolitinib; belumosudil (ROCK2 inhibitor) approved 2021

Graft-Versus-Leukemia (GVL) Effect

• Major reason allogeneic HSCT can be curative for leukemia
• Donor Lymphocyte Infusion (DLI): infusion of additional donor T cells to enhance GVL for relapse or molecular relapse
• Balance between GVL and GVHD is central challenge

Infectious Complications After Transplant

• CMV prophylaxis/preemptive therapy: letermovir (prophylaxis), ganciclovir/valganciclovir (treatment)
• PCP prophylaxis: TMP-SMX (preferred), or pentamidine/atovaquone
• Antifungal prophylaxis: fluconazole (engraftment phase); posaconazole/voriconazole for high-risk allo (covers Aspergillus)

CAR-T Cell Therapy (Emerging/Modern)

• Patient's T cells collected → genetically engineered to express CAR (chimeric antigen receptor) targeting tumor antigen (e.g., CD19, BCMA)
• Infused back → CAR-T cells attack tumor

• Cytokine release syndrome (CRS): fever, hypotension, hypoxia → treat with tocilizumab (anti-IL6R) ± steroids
• ICANS (Immune effector cell-associated neurotoxicity syndrome): confusion, seizures → treat with steroids; tocilizumab does not help ICANS

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SUMMARY TABLE: MUST-KNOW HIGH-YIELD FACTS

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