hematology 1) A 25-year-old woman presents with fatigue, pallor, and history of menorrhagia. Hb is low with microcytic hypochromic RBCs. Write about Diagnosis Causes Pathogenesis Peripheral smear findings Differences between B12 and folate deficiency Clinical features 2) patient presents with: • Jaundice • Pallor • Splenomegaly Lab: • ↑ Reticulocyte count • ↑ Unconjugated bilirubin write about Diagnosis Classification (intrinsic vs extrinsic) Pathogenesis Laboratory findings Peripheral smear findings 3)young adult presents with: • Painless lymphadenopathy • Fever, weight loss Write about Diagnosis Pathogenesis Morphology Clinical features Differences from Non-Hodgkin lymphoma 4) 25-year-old female presents with: • Fatigue • Pallor • History of heavy menstrual bleeding Lab: • ↓ Hb • Microcytic hypochromic anemia Write about Diagnosis Define anemia Causes of iron deficiency anemia Pathogenesis Laboratory findings Peripheral smear features Clinical features 5) A child presents with: • Recurrent joint bleeding • Prolonged bleeding after minor trauma Write about Diagnosis Types of hemophilia Pathogenesis Laboratory findings Clinical features Short answer 1)define anemia and classification of anemia 2)Aplastic anemia 3)classify non hodgkin lymphoma 4)PNH( paraoxysomal nocturnal hemoglobinuria) 5)diffferential diagnosis of microcytic anemia and how you will differentiate 6)describe etiopathogenesis, clinical features of ITP 7)Anemia of chronic disease 8)burkitt lymphoma Vsaq 1)phialdephia chromosome 2)myeloblast verses lymphoblast 3)classification of AML 4)reed sternberg cell 5)hemolytic verses non hemolytic anemia

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HEMATOLOGY - Comprehensive Notes

LONG QUESTIONS

Q1 & Q4 - Iron Deficiency Anemia (IDA)

(Note: Q1 and Q4 describe the same clinical scenario. Q4 asks for "define anemia" as well - addressed there.)

Diagnosis

Iron Deficiency Anemia (IDA) - microcytic hypochromic anemia due to insufficient iron for hemoglobin synthesis. This is the most common nutritional deficiency in the world, affecting ~10% of people in higher-resource countries and 25-50% in lower-resource countries.

Define Anemia (Q4)

Anemia is defined as a reduction in the oxygen-transporting capacity of the blood, usually due to a reduction in the number of red cells or their hemoglobin content, resulting in reduced delivery of oxygen to tissues. WHO criteria: Hb < 13 g/dL in adult men, < 12 g/dL in adult women, < 11 g/dL in pregnant women.

Causes of Iron Deficiency Anemia

Chronic blood loss (most important cause in higher-resource countries)
- Gastrointestinal: peptic ulcers, colon cancer, hemorrhoids
- Female genital tract: menorrhagia, metrorrhagia, endometrial cancer
Inadequate dietary intake - vegetarian diets (poor bioavailability), infants on exclusive milk feeding, elderly, food insecurity
Increased demand - pregnancy, infancy, rapid growth
Malabsorption - celiac disease, various gastritis, post-gastrectomy

Pathogenesis

Iron metabolism background:

Normal total body iron: 2.5 g (women) to 3.5 g (men)
~80% in hemoglobin, myoglobin, and iron-containing enzymes (catalase, cytochromes)
15-20% in storage pool (ferritin + hemosiderin) in macrophages of liver, spleen, bone marrow
Iron transported in plasma bound to transferrin (normally 33% saturated); normal serum iron ~120 µg/dL in men, ~100 µg/dL in women; total iron-binding capacity (TIBC): 300-350 µg/dL
Iron loss: 1-2 mg/day via epithelial shedding; replaced by dietary absorption

Regulation: Iron absorption occurs in the duodenum:

Ferric iron (Fe³⁺) reduced to ferrous (Fe²⁺) by duodenal cytochrome B
Fe²⁺ transported into enterocytes via DMT1 (divalent metal transporter-1)
Fe²⁺ exported to plasma via ferroportin
Plasma hepcidin (secreted by liver) negatively regulates ferroportin, controlling absorption

Sequence of iron depletion in IDA:

Stage 1: Iron stores depleted → serum ferritin falls, bone marrow iron absent (stainable iron disappears)
Stage 2: Serum iron falls, transferrin rises (↑ TIBC), transferrin saturation falls
Stage 3: Hemoglobin synthesis impaired → microcytic hypochromic anemia, impaired cognition and work performance, reduced immunocompetence

Laboratory Findings

Parameter	Finding in IDA
Hemoglobin	Decreased
MCV	Low (<80 fL) - microcytic
MCH/MCHC	Decreased - hypochromic
Serum iron	Decreased
Serum ferritin	Decreased (earliest marker)
TIBC (Transferrin)	Increased
Transferrin saturation	Decreased (<16%)
Reticulocyte count	Low/normal (bone marrow blunted)
Platelet count	Often elevated (reactive thrombocytosis)
Serum erythropoietin	Elevated
Bone marrow iron stain	Absent stainable iron (gold standard)

Peripheral Smear Findings

Microcytes - smaller than normal RBCs (smaller than lymphocyte nucleus)
Hypochromia - enlarged central pallor (>1/3 of cell diameter), pale cells
Anisocytosis - variation in size
Poikilocytosis - variation in shape (elliptocytes, target cells)
Pencil cells (cigar cells) - elongated thin red cells
Low reticulocyte count
Target cells occasionally seen

Clinical Features

General:

Weakness, fatigue, listlessness, pallor
Dyspnea, palpitations (in severe cases)

Specific to IDA (long-standing):

Koilonychia - spoon-shaped nails (thinning, flattening, spooning of fingernails)
Pica - compulsion to consume nonfoodstuffs (dirt, clay, ice - pagophagia)
Angular stomatitis (cheilosis) and glossitis
Plummer-Vinson syndrome - IDA + dysphagia (esophageal webs) in middle-aged women

B12 vs Folate Deficiency - Differences

Feature	Vitamin B12 Deficiency	Folate Deficiency
Cause	Pernicious anemia (anti-intrinsic factor Ab), gastrectomy, ileal disease, Crohn's disease, strict veganism	Poor diet (elderly, alcoholics), malabsorption (celiac), drugs (methotrexate, phenytoin), pregnancy
Anemia type	Megaloblastic (macrocytic)	Megaloblastic (macrocytic)
Neurological	YES - subacute combined degeneration of spinal cord (posterior & lateral columns), peripheral neuropathy, dementia	NO neurological involvement
Storage	Stored in liver; 5-20 years reserve	Stores last only ~3-4 months
Absorption site	Distal ileum (via intrinsic factor)	Upper 1/3 of small intestine (jejunum)
Serum level	Low B12	Low folate
Anti-intrinsic factor Ab	Present (pernicious anemia)	Absent
Homocysteine	Elevated	Elevated
Methylmalonic acid (MMA)	Elevated	Normal
Schilling test	Abnormal (corrected with intrinsic factor)	Normal
GI symptoms	Present (glossitis, diarrhea)	Present (similar)
Treatment	B12 injection/oral B12	Folic acid supplementation
Peripheral smear	Macroovalocytes, hypersegmented neutrophils (≥5 lobes), pancytopenia	Same smear findings, NO neurological changes

Q2 - Hemolytic Anemia

Clinical picture: Jaundice + Pallor + Splenomegaly + ↑ Reticulocytes + ↑ Unconjugated bilirubin

Diagnosis

Hemolytic Anemia - a diverse group of disorders characterized by accelerated red cell destruction (RBC lifespan shortened from normal 120 days, sometimes markedly so), leading to anemia with compensatory erythroid hyperplasia and reticulocytosis.

Classification

A. By Site of Defect: Intrinsic (Intracorpuscular) vs Extrinsic (Extracorpuscular)

Intrinsic (Intracorpuscular) - Defect within the RBC:

Membrane defects - Hereditary spherocytosis, elliptocytosis, PNH (acquired)
Enzyme defects - G6PD deficiency, pyruvate kinase deficiency
Hemoglobin defects - Sickle cell disease, thalassemia

Extrinsic (Extracorpuscular) - Defect outside the RBC:

Immune - Autoimmune hemolytic anemia (AIHA), transfusion reactions, hemolytic disease of newborn
Non-immune mechanical - Microangiopathic hemolytic anemia (TTP, HUS, DIC), prosthetic heart valves
Infections - Malaria, Clostridium
Hypersplenism
Drugs/toxins

B. By Site of Destruction: Extravascular vs Intravascular

Feature	Extravascular Hemolysis	Intravascular Hemolysis
Site	Spleen/liver macrophages	Within blood vessels
Cause	Spherocytosis, AIHA, G6PD	Mechanical (defective valves), complement (PNH), toxins
Jaundice	Yes (unconjugated bilirubin ↑)	Yes
Splenomegaly	Prominent ("work hyperplasia")	Less prominent
Hemoglobinemia/uria	Absent	Present
Hemosiderinuria	Absent	Present (chronic)
Iron deficiency	Not a feature (recycled)	Can occur (chronic)
Haptoglobin	Decreased	Markedly decreased

Pathogenesis

Extravascular hemolysis (as in this patient):

RBC lifespan shortened → increased destruction in spleen
Spleen macrophages phagocytose abnormal/opsonized/poorly deformable RBCs
Hemoglobin degraded in macrophages → heme → biliverdin → unconjugated bilirubin (→ jaundice)
Liver cannot keep up with load → ↑ unconjugated (indirect) bilirubin
Long-standing → ↑ bilirubin excretion in bile → pigment gallstones (calcium bilirubinate)
Kidney responds with ↑ erythropoietin → ↑ reticulocytes in peripheral blood
Marrow shows erythroid hyperplasia; severe cases → extramedullary hematopoiesis in liver, spleen, lymph nodes
Splenomegaly: "work hyperplasia" of splenic macrophages + congestion of splenic cords

Laboratory Findings

Test	Result
Hb	Decreased
Reticulocyte count	↑↑ (hallmark)
Unconjugated (indirect) bilirubin	↑↑
Serum LDH	↑ (LDH-1 from RBCs)
Haptoglobin	↓ (binds free hemoglobin, cleared by macrophages)
Serum K⁺	↑ (intracellular RBC content released)
Urinary urobilinogen	↑
Direct Coombs test	Positive (immune hemolysis) / Negative (non-immune)
Peripheral smear	Polychromasia, spherocytes, sickle cells, etc. (depending on cause)
Bone marrow	Erythroid hyperplasia (M:E ratio reversed)
CO (carboxyhemoglobin)	↑ (from heme ring opening)

Peripheral Smear Findings

General findings in all hemolytic anemias:

Polychromasia (reticulocytes - blue-grey cells)
Increased reticulocyte count

Type-specific findings:

Hereditary spherocytosis: Small, dark spherocytes with no central pallor
Sickle cell disease: Sickled cells (crescent-shaped), target cells, Howell-Jolly bodies
Thalassemia: Target cells, hypochromic microcytes, nucleated RBCs
Microangiopathic hemolytic anemia (MAHA): Schistocytes (fragmented RBCs, helmet cells, triangle cells)
Autoimmune hemolytic anemia: Spherocytes + positive Coombs test
G6PD deficiency: Bite cells, Heinz bodies (on supravital stain)
Malaria: Parasites within RBCs (Plasmodium)

Q3 - Hodgkin Lymphoma

Clinical picture: Young adult + Painless lymphadenopathy + Fever, weight loss (B symptoms)

Diagnosis

Hodgkin Lymphoma (HL) - a malignant neoplasm of germinal center B cells characterized by the presence of distinctive Reed-Sternberg (RS) cells set in a reactive cellular background.

Pathogenesis

Cell of origin: Elegant microdissection studies of single RS cells showed identical immunoglobulin gene rearrangements with somatic hypermutation in all RS cells → HL arises from germinal center B cells
EBV involvement: EBV genome found in RS cells in up to 70% of mixed-cellularity subtype; identical integration site in all RS cells in a given case → EBV infection precedes transformation; likely one of several oncogenic steps
Cytokines from RS cells:
- IL-5 → attracts eosinophils
- TGF-β → fibrogenic (→ nodular sclerosis collagen bands)
- IL-13 → autocrine RS cell growth stimulation
Immune evasion: RS cells express:
- High levels of PD-L1 and PD-L2 (checkpoint inhibitors blocking T-cell response)
- Loss of β2-microglobulin → failure to express class I MHC → evade cytotoxic T cells
- Chromosome 9p amplification containing PD-L1/PD-L2 genes

Morphology

Reed-Sternberg (RS) Cell - the sine qua non (pathognomonic finding):

Very large cell (15-45 µm diameter)
Enormous multilobate nucleus with exceptionally prominent nucleoli
Abundant eosinophilic cytoplasm
Classic "owl-eye" appearance - two mirror-image nuclei/nuclear lobes each with a large acidophilic nucleolus surrounded by a clear halo
Immunophenotype: CD15+, CD30+, CD45-, B-cell markers-, T-cell markers-

WHO Classification - 5 Subtypes:

Subtype	Frequency	Key Features
Nodular Sclerosis	Most common (65-70%)	Adolescents/young adults; collagen bands dividing lymph node into nodules; lacunar cells (RS variant); mediastinal involvement; equal sex ratio
Mixed Cellularity	2nd most common (20-25%)	Older males; classic RS cells; mixed infiltrate (eosinophils, plasma cells, lymphocytes, histiocytes); strong EBV association (70%)
Lymphocyte Rich	Rare (5%)	Best prognosis; few RS cells; abundant lymphocytes
Lymphocyte Depletion	Rarest (<1%)	Worst prognosis; numerous RS cells, few lymphocytes; older patients with HIV
Nodular Lymphocyte Predominant	5%	"Popcorn cells" (lymphocytic-histiocytic RS variants); expresses germinal center B-cell markers (CD20+, BCL6+, CD15-, CD30-); indolent

First 4 subtypes = Classic Hodgkin Lymphoma (cHL)

Clinical Features

Painless lymphadenopathy - most common presentation, often cervical/supraclavicular/mediastinal
Contiguous spread - orderly, stepwise spread to adjacent lymph node groups
B symptoms (present in ~40%; associated with worse prognosis):
- Fever (>38°C) - especially Pel-Ebstein fever (cyclical high fever)
- Night sweats
- Unexplained weight loss >10% body weight in 6 months
Mediastinal widening (especially nodular sclerosis)
Pruritus (due to histamine from eosinophils/basophils)
Alcohol-induced pain at lymph node sites (characteristic but uncommon)
Splenomegaly, hepatomegaly in advanced disease
Ann Arbor Staging I-IV (A = no B symptoms, B = B symptoms present)
Excellent overall prognosis with modern ABVD chemotherapy ± radiotherapy; >90% cure rate in early stages

Differences: Hodgkin vs Non-Hodgkin Lymphoma

Feature	Hodgkin Lymphoma	Non-Hodgkin Lymphoma
Age	Bimodal: young adults (15-35) & >55	Any age, increases with age
Nodes involved	Single axial group (cervical, mediastinal, paraaortic)	Multiple peripheral lymph node groups
Spread	Orderly, contiguous	Non-contiguous, unpredictable
Mesenteric nodes/Waldeyer ring	Rarely involved	Commonly involved
Extranodal	Uncommon	Common
RS cells	Present (pathognomonic)	Absent
Cell of origin	Germinal center B cell	B cells (majority), T cells, NK cells
EBV association	Mixed cellularity (70%)	Burkitt lymphoma, some others
B symptoms	Common	Less common
Bone marrow	Rarely involved early	Often involved
CNS	Rarely	Some subtypes
Mediastinal mass	Common (nodular sclerosis)	Less common (T-ALL/lymphoblastic)
Prognosis	Generally excellent (curable)	Variable (indolent to highly aggressive)
Treatment	ABVD, radiation	Varies by subtype (R-CHOP, etc.)
WHO marker	CD15+, CD30+	Varies by type

Q5 - Hemophilia

Clinical picture: Child + Recurrent joint bleeding + Prolonged bleeding after minor trauma

Diagnosis

Hemophilia A (Factor VIII deficiency) - most likely. Hemophilia is a hereditary bleeding disorder occurring almost exclusively in males due to deficiency of clotting factors.

Types of Hemophilia

Type	Factor Deficiency	Inheritance	Frequency
Hemophilia A (Classic)	Factor VIII	X-linked recessive	85% of cases; 1 in 10,000 males
Hemophilia B (Christmas disease)	Factor IX	X-linked recessive	15% of cases; clinically indistinguishable from A
Hemophilia C	Factor XI	Autosomal recessive	Rare; milder bleeding

Severity Classification (Hemophilia A/B):

Severity	Factor Level	Clinical Features
Severe	<1% of normal	Spontaneous hemarthroses, muscle hematomas
Moderate	1-5%	Bleeding with minor trauma
Mild	5-40%	Bleeding only with significant trauma or surgery

Pathogenesis

Factor VIII (large multimer component for vWF binding + smaller 230kDa coagulant component) is encoded on the X chromosome → X-linked recessive
Males have only one X chromosome → a single mutated allele causes disease
Females are carriers (one normal + one defective X) - rarely symptomatic (may have mild trait due to lyonization)
~30% of cases arise from new mutations (no family history)
Factor VIII is essential for the intrinsic pathway of coagulation (tenase complex with factor IXa activates factor X)
Deficiency → inadequate thrombin generation → unstable clot formation → prolonged/excessive bleeding
Factor IX (Hemophilia B): Also part of intrinsic pathway (factor IXa:VIIIa = intrinsic tenase complex); deficiency clinically identical to hemophilia A
Bleeding tendency severity correlates with degree of factor deficiency

Laboratory Findings

Test	Hemophilia A/B	Interpretation
aPTT (PTT)	Prolonged	Intrinsic pathway defect
PT (Prothrombin time)	Normal	Extrinsic pathway intact
Thrombin time	Normal
Platelet count	Normal
Bleeding time	Normal	Platelet function intact
Mixing study	PTT corrects with normal plasma	Distinguishes from inhibitor
Specific factor assay	Factor VIII ↓↓ (Hemophilia A) / Factor IX ↓↓ (Hemophilia B)	Confirms diagnosis and type
vWF assay	Normal	Differentiates from von Willebrand disease

Clinical Features

Hemarthroses (joint bleeds) - most characteristic; knees, elbows, ankles most commonly affected
- Recurrent → chronic hemophilic arthropathy → progressive joint deformity, ankylosis
Muscle hematomas - large, deep, compressive
Prolonged bleeding after minor trauma - tooth extraction, minor cuts
Retroperitoneal/intramuscular hematomas - can be life-threatening
Intracranial hemorrhage - may be spontaneous in severe disease; leading cause of death
No petechiae - platelet function is intact; petechiae are characteristic of platelet/vascular disorders, not hemophilia
Pseudotumors - progressive cystic hematomas, especially in bone (femur, pelvis)
Compartment syndrome from muscle bleeds

Complications of treatment:

~15% of severe hemophilia A patients develop inhibitory antibodies (neutralizing Ab against factor VIII) after replacement therapy → PTT fails to correct with mixing study → treated with bypassing agents (Factor VIIa, FEIBA) or bispecific antibody (emicizumab)
Historically: HIV and hepatitis C transmission via plasma-derived products (before recombinant era)

Treatment:

Recombinant Factor VIII (hemophilia A) or Factor IX (hemophilia B)
Emicizumab (bispecific antibody mimicking Factor VIII) for hemophilia A with or without inhibitors
DDAVP (desmopressin) for mild hemophilia A (releases stored vWF and Factor VIII)

SHORT ANSWER QUESTIONS

SAQ 1 - Define Anemia and Classification

Definition: Anemia is a reduction in oxygen-transporting capacity of blood, reflected as a decrease in hemoglobin concentration, hematocrit, or red cell count below the normal reference range for age and sex.

WHO Criteria:

Adult males: Hb < 13 g/dL
Adult non-pregnant females: Hb < 12 g/dL
Pregnant females: Hb < 11 g/dL

Classification:

A. By Pathogenesis:

Category	Mechanism	Examples
Increased destruction	Hemolytic anemia	Hereditary spherocytosis, sickle cell, AIHA, G6PD, malaria
Blood loss	Acute or chronic	GI bleeding, trauma, menorrhagia
Decreased production	Failure of erythropoiesis	IDA, megaloblastic, aplastic, ACD

B. By Morphology (MCV-based):

Type	MCV	Causes
Microcytic hypochromic	<80 fL	IDA, thalassemia, ACD (sometimes), sideroblastic anemia, lead poisoning
Normocytic normochromic	80-100 fL	Acute blood loss, hemolytic anemia, aplastic anemia, ACD, early IDA
Macrocytic	>100 fL	Megaloblastic (B12/folate deficiency), liver disease, hypothyroidism, drugs (hydroxyurea)

C. By Bone Marrow Response:

Regenerative (hyperplastic): ↑ reticulocytes → blood loss, hemolytic anemia
Hypoplastic/aplastic: ↓ reticulocytes → aplastic anemia, iron deficiency, megaloblastic

SAQ 2 - Aplastic Anemia

Definition: Aplastic anemia is a disorder in which multipotent myeloid stem cells are suppressed, leading to bone marrow failure and pancytopenia (↓ RBC, ↓ WBC, ↓ platelets). The marrow is often virtually devoid of recognizable hematopoietic elements.

Etiology:

Category	Causes
Idiopathic	~50% of cases
Acquired	Radiation, chemotherapy, benzene, chloramphenicol, NSAIDs, gold salts
Viral	EBV, CMV, hepatitis (seronegative hepatitis most common viral cause), HIV, parvovirus B19
Immune-mediated	T cell-mediated autoimmune attack on stem cells
Inherited	Fanconi anemia (DNA repair defects), dyskeratosis congenita (telomerase defects), Shwachman-Diamond syndrome

Pathogenesis (two mechanisms):

Immune-mediated: Stem cells antigenically altered by drugs/infections → activated Th1 cells produce cytokines (IFN-γ, TNF) → suppress hematopoietic progenitors. Evidence: immunosuppressive therapy (anti-thymocyte globulin + cyclosporine) restores hematopoiesis in 60-70% of patients
Intrinsic stem cell defects: 5-10% have inherited telomerase defects → premature senescence of HSCs; additional 50% have abnormally short telomeres

Clinical Features:

Insidious onset - gradual worsening weakness, pallor, dyspnea (anemia)
Thrombocytopenia → petechiae, ecchymoses, mucosal bleeding
Neutropenia → recurrent serious infections
No splenomegaly (if present, consider another diagnosis)
Pancytopenia with hypocellular bone marrow (fatty marrow on trephine biopsy)

Laboratory:

Pancytopenia (all cell lines ↓)
Reticulocytopenia (low reticulocyte count)
Bone marrow biopsy: hypocellular/fatty marrow (<25% cellularity) - diagnostic
Normal morphology of remaining cells

Treatment:

Hematopoietic stem cell transplantation (HSCT) - curative, preferred in patients <40 years
Immunosuppression - anti-thymocyte globulin (ATG) + cyclosporine for non-transplant candidates
Supportive: transfusions (minimize before HSCT to prevent sensitization), G-CSF

SAQ 3 - Classification of Non-Hodgkin Lymphoma

NHL is classified by the WHO classification based on cell of origin (B cell vs T cell/NK cell) and stage of differentiation.

A. B-Cell Neoplasms (most common; ~85% of NHLs):

Precursor B-cell:

B-lymphoblastic leukemia/lymphoma (B-ALL)

Mature (peripheral) B-cell:

Lymphoma	Key Feature
CLL/SLL	Most common leukemia in adults; CD5+, CD23+; indolent
Follicular lymphoma	t(14;18) → BCL2 overexpression; "follicular" pattern; indolent
Mantle cell lymphoma	t(11;14) → Cyclin D1 overexpression; CD5+, CD23-; moderately aggressive
Diffuse large B-cell lymphoma (DLBCL)	Most common aggressive NHL; BCL6 mutations; CD20+
Burkitt lymphoma	t(8;14) → MYC overexpression; starry sky pattern; highly aggressive; EBV-associated
Marginal zone lymphoma (MALToma)	H. pylori-associated gastric lymphoma; indolent
Multiple myeloma	Plasma cell neoplasm; M protein; bone lesions

B. T-Cell and NK-Cell Neoplasms (~15% of NHLs):

Precursor T-cell:

T-lymphoblastic leukemia/lymphoma (T-ALL) - adolescent males, thymic mass

Mature T-cell:

Peripheral T-cell lymphoma (PTCL)
Anaplastic large cell lymphoma (ALCL) - ALK+/ALK-
Mycosis fungoides / Sézary syndrome (cutaneous T-cell)
Adult T-cell leukemia/lymphoma (HTLV-1 associated)
NK/T-cell lymphoma, nasal type (EBV-associated)

Clinical Behavior Classification:

Indolent: Follicular lymphoma, CLL/SLL, MZL - slow growing, long survival, difficult to cure
Aggressive: DLBCL, mantle cell - fast growing, potentially curable with chemotherapy
Highly aggressive: Burkitt, B-ALL/T-ALL - fastest growing human tumors; intensive chemo → cure possible

SAQ 4 - Paroxysmal Nocturnal Hemoglobinuria (PNH)

Definition: PNH is an acquired hemolytic anemia caused by mutations in PIGA gene (X-linked), which encodes an enzyme required for synthesis of phosphatidylinositol glycan (PIG) membrane anchor proteins.

Pathogenesis:

PIGA mutation in an early hematopoietic progenitor → progeny cells (RBCs, WBCs, platelets) lack GPI-anchored proteins, including key complement regulatory proteins:
- CD55 (DAF - decay accelerating factor) - inhibits C3 convertase
- CD59 (protectin) - inhibits C5b-9 membrane attack complex (MAC)
Without these inhibitors → RBCs are inordinately sensitive to complement-mediated lysis (C5b-C9 MAC)
Nocturnal hemolysis: During sleep, CO2 retention → slight ↓ pH → enhanced complement fixation → early morning hemoglobinuria (red/brown urine on waking)

Clinical Features:

Chronic intravascular hemolysis → anemia, hemoglobinuria, hemosiderinuria
Thrombosis - most feared complication; especially abdominal vessels: portal vein thrombosis, hepatic vein thrombosis (Budd-Chiari syndrome); also cerebral venous sinus thrombosis
Iron deficiency (from chronic urinary hemoglobin/iron loss)
Association with aplastic anemia (may precede or follow PNH)
Pancytopenia

Lab:

Flow cytometry showing absent CD55/CD59 on RBCs and granulocytes (diagnostic gold standard; replaced old Ham test/sucrose lysis test)
↑ LDH, ↑ unconjugated bilirubin, ↓ haptoglobin
Hemoglobinuria, hemosiderinuria

Treatment:

Eculizumab (anti-C5 monoclonal Ab) - blocks MAC formation; reduces hemolysis and thrombosis dramatically; risk of Neisseria (meningococcal) infection → vaccination mandatory
Ravulizumab (longer-acting anti-C5)
HSCT for severe cases/aplastic anemia-associated PNH

SAQ 5 - Differential Diagnosis of Microcytic Anemia and Differentiation

Causes of microcytic hypochromic anemia (MICRO mnemonic):

Iron deficiency anemia (IDA) - most common worldwide
Thalassemia (α or β)
Anemia of chronic disease (ACD) - usually normocytic, occasionally microcytic
Sideroblastic anemia (X-linked, lead poisoning, alcohol)
Lead poisoning

Differentiating Features:

Parameter	IDA	Thalassemia	ACD	Sideroblastic
Serum Iron	↓↓	Normal/↑	↓	↑
TIBC/Transferrin	↑↑	Normal	↓	Normal
Transferrin saturation	↓ (<16%)	Normal/↑	↓	↑
Serum Ferritin	↓↓	Normal/↑	↑↑	↑
Bone marrow iron	Absent	Increased	↑ (blocked)	Ringed sideroblasts
RDW (anisocytosis)	↑ (high)	Normal/mildly ↑	Normal	↑
RBC count	↓	Normal/↑	↓	↓
MCV	Low	Very low (disproportionate to anemia)	Low-normal	Low-normal
Hb electrophoresis	Normal	Abnormal (↑ HbA2 in β-thal)	Normal	Normal
Mentzer index (MCV/RBC)	>13 → IDA	<13 → Thalassemia	-	-
Peripheral smear	Pencil cells, target cells	Target cells, nucleated RBCs, basophilic stippling	Normochromic or mild hypochromia	Basophilic stippling
Reticulocyte	Low	Normal-↑	Low-normal	Low
Response to iron	Yes	No	No (unless combined)	No
Specific marker	-	↑ HbA2, ↑ HbF	↑ ESR/CRP, underlying disease	Ringed sideroblasts on BM

Key distinguishing points:

IDA vs Thalassemia: Mentzer Index (MCV/RBC count): >13 = IDA; <13 = thalassemia. RBC count is relatively preserved in thalassemia (high number of small cells) but low in IDA
IDA vs ACD: Ferritin is the key - low in IDA, high (acute-phase reactant) in ACD; TIBC high in IDA, low/normal in ACD
Sideroblastic: Ringed sideroblasts on bone marrow biopsy (iron-laden mitochondria around nucleus)

SAQ 6 - ITP: Etiopathogenesis and Clinical Features

Definition: Immune Thrombocytopenic Purpura (ITP) - also called Immune Thrombocytopenia - is an autoimmune disorder characterized by immune-mediated platelet destruction and/or impaired platelet production, resulting in isolated thrombocytopenia.

Types:

Primary ITP: No identifiable cause
Secondary ITP: Associated with SLE, HIV, HCV, H. pylori, CLL, drugs
Acute ITP: Children; often post-viral; self-limiting (2-6 weeks)
Chronic ITP: Adults (especially women 20-40 years); persists >12 months

Etiopathogenesis:

Antiplatelet antibodies (IgG) - mainly anti-GPIIb/IIIa and anti-GPIb/IX (glycoprotein complexes on platelet surface) - produced by autoreactive B cells
Antibody-coated platelets are recognized by Fc receptors on splenic macrophages → phagocytosis → platelet destruction (extravascular hemolysis equivalent)
Megakaryocyte impairment: Some antibodies also cross-react with megakaryocyte antigens → impaired platelet production in bone marrow
T-cell mediated: CD4+ Th1 and Th17 cells are activated; regulatory T cells (Tregs) are deficient → loss of immune tolerance
Complement may contribute to platelet opsonization and destruction

Clinical Features:

Bleeding manifestations (platelet-type bleeding - mucocutaneous):

Petechiae - pinpoint non-blanching hemorrhages in skin/mucous membranes (characteristic of thrombocytopenia)
Purpura - larger areas of skin hemorrhage
Ecchymoses - bruising, often spontaneous
Epistaxis (nosebleeds)
Gingival bleeding
Menorrhagia - in women
GI/GU bleeding - in severe cases
Intracranial hemorrhage - rare but life-threatening (platelet count <10,000/µL)

Absence of:

Splenomegaly (spleen is normal size unless secondary ITP with underlying disease)
Fever, lymphadenopathy (helps distinguish from other thrombocytopenias)

Lab:

Isolated thrombocytopenia (platelets <100,000/µL)
Normal PT, PTT (coagulation tests normal)
Peripheral smear: reduced platelets, megathrombocytes (large platelets)
Bone marrow: increased megakaryocytes (compensatory)
Antiplatelet antibodies (positive in ~60-80%; low sensitivity/specificity)
ITP is a diagnosis of exclusion

Treatment:

Corticosteroids (prednisone) - first line
IVIG - rapid response (blocks Fc receptors on macrophages)
Anti-D (Rh0D immunoglobulin) - in Rh+ patients
Splenectomy - removes main site of platelet destruction and antibody production; 2nd line
Thrombopoietin receptor agonists (romiplostim, eltrombopag) - stimulate platelet production
Rituximab (anti-CD20) - destroys antibody-producing B cells

SAQ 7 - Anemia of Chronic Disease (ACD)

Also known as: Anemia of Chronic Inflammation (ACI) - most common form of anemia in hospitalized patients.

Conditions associated:

Chronic infections: osteomyelitis, bacterial endocarditis, lung abscess, tuberculosis
Chronic immune disorders: rheumatoid arthritis, SLE, Crohn's disease
Malignancies: Hodgkin lymphoma, carcinomas of lung and breast

Pathogenesis (hepcidin-central model):

Inflammatory cytokines (IL-6, IL-1, TNF-α) → stimulate liver to produce hepcidin ↑↑
Hepcidin downregulates ferroportin on macrophages → iron trapped in macrophages (↑ ferritin storage) → iron NOT available for erythropoiesis (functional iron deficiency)
Blunted erythropoietin response - inflammatory cytokines suppress EPO production by the kidney
Direct suppression of erythroid progenitors by TNF-α and IFN-γ

Key features (compared to IDA):

Parameter	ACD	IDA
Serum iron	↓	↓
TIBC	↓ or normal	↑
Serum ferritin	↑ (acute phase protein)	↓
Bone marrow iron	Increased (trapped)	Absent
Transferrin saturation	↓	↓
MCV/morphology	Usually normocytic-normochromic; occasionally microcytic	Microcytic hypochromic
Hepcidin	↑↑	↓
EPO response	Blunted	Appropriately elevated

Clinical Features:

Usually mild to moderate anemia (Hb rarely <8 g/dL unless severe underlying disease)
Signs and symptoms of the underlying chronic disease
Mild hypochromia and microcytosis (in some cases)

Treatment:

Treat the underlying condition (definitive)
Erythropoiesis-stimulating agents (ESA) + iron supplementation (adjunct)
Blood transfusion (severe, symptomatic cases)

SAQ 8 - Burkitt Lymphoma

Definition: Burkitt lymphoma is a highly aggressive B-cell NHL characterized by translocation of the MYC oncogene (chromosome 8) and one of the immunoglobulin loci.

Epidemiology:

Three forms: Endemic (African), Sporadic, Immunodeficiency-associated
Mainly affects children and young adults
Among the fastest growing human tumors (doubling time ~24-48 hours)

Pathogenesis:

t(8;14)(q24;q32) - most common; fuses MYC (chr 8) with IgH locus (chr 14) → MYC overexpression (~80% of cases)
Variant: t(2;8) - MYC fused to κ light chain; t(8;22) - MYC fused to λ light chain
MYC is a master regulator of Warburg metabolism (aerobic glycolysis) → promotes rapid cell growth and proliferation
EBV - present in nearly all endemic cases; ~20% of sporadic cases (EBV genome identical in all tumor cells → precedes transformation)

Morphology:

Intermediate-sized cells with round/oval nuclei and 2-5 distinct nucleoli
Moderate amount of basophilic/amphophilic cytoplasm with small lipid vacuoles
Very high mitotic rate + high apoptosis → "Starry sky" pattern (benign macrophages with ingested nuclear debris surrounded by clear space giving "stars" amid "sky" of tumor cells)
Monotonous appearance (uniform cells)

Immunophenotype:

Surface IgM+, CD20+, CD10+, BCL6+ (germinal center B-cell markers)
BCL2- (distinguishes from follicular lymphoma)
Ki-67 (proliferation index) ~100%

Clinical Features:

Endemic (African): Jaw/maxillary mass in children; abdominal involvement
Sporadic (North American): Abdominal mass most common (bowel, retroperitoneum, ovaries); ~30% of childhood NHLs in USA
Immunodeficiency-associated: HIV-positive patients
Leukemic presentation occasionally (distinguish from B-ALL by immunophenotype/cytogenetics)
Highly curable with very intensive chemotherapy (>90% in children); adults have worse outcomes

VERY SHORT ANSWER QUESTIONS (VSAQs)

VSAQ 1 - Philadelphia Chromosome

The Philadelphia chromosome is a shortened chromosome 22 resulting from a reciprocal translocation t(9;22)(q34;q11).

The ABL proto-oncogene (chromosome 9) is fused with the BCR gene (chromosome 22)
Product: BCR-ABL fusion gene → encodes a constitutively active BCR-ABL tyrosine kinase
BCR-ABL phosphorylates multiple substrates → activates RAS, JAK-STAT, PI3K pathways → uncontrolled proliferation, inhibited apoptosis

Associated diseases:

Chronic Myeloid Leukemia (CML) - present in >95% of cases; hallmark of CML
B-ALL - present in ~25% of adult B-ALL; ~5% of pediatric B-ALL; associated with worse prognosis

Clinical significance of CML:

High granulocyte count, high platelet count, splenomegaly
Without treatment → transforms to blast crisis (B-ALL or AML)
Treatment: BCR-ABL tyrosine kinase inhibitors (TKIs) - imatinib (Gleevec), dasatinib, nilotinib → dramatic disease control; CML was the first cancer successfully treated with a molecularly targeted drug

VSAQ 2 - Myeloblast vs Lymphoblast

Feature	Myeloblast	Lymphoblast
Size	Larger (14-20 µm)	Smaller (10-18 µm)
Nucleus	Round-oval; fine chromatin; 2-5 prominent nucleoli	Round; finely stippled/condensed chromatin; small/inconspicuous nucleoli
Cytoplasm	Moderate amount; azurophilic granules present	Scant basophilic cytoplasm; agranular
Auer rods	Present (pathognomonic for AML)	Absent
N:C ratio	Moderate	High (large nucleus relative to cytoplasm)
Special stains	MPO+ (myeloperoxidase), Sudan Black B+	MPO-, TdT+, PAS+
Immunophenotype	CD13+, CD33+, CD117 (c-kit)+, CD34+	B-ALL: CD10, CD19, CD22+; T-ALL: CD2, CD3, CD7+; Both: TdT+
Disease	Acute Myeloid Leukemia (AML)	Acute Lymphoblastic Leukemia (ALL)

VSAQ 3 - Classification of AML

AML is classified by the WHO 2022 classification (superceding old FAB classification):

A. WHO Classification (2022) - based on genetics/etiology:

AML with recurrent genetic abnormalities:
- AML with t(8;21) [RUNX1::RUNX1T1]
- AML with inv(16) or t(16;16) [CBFB::MYH11]
- Acute promyelocytic leukemia (APL) with t(15;17) [PML::RARA] - treated with ATRA + arsenic
- AML with t(9;11) [KMT2A::MLLT3]
- AML with t(6;9) [DEK::NUP214]
- AML with inv(3) or t(3;3)
- AML with t(1;22) (megakaryoblastic)
- AML with BCR::ABL1
- AML with mutated NPM1
- AML with biallelic CEBPA mutations
- AML with mutated RUNX1
AML with myelodysplasia-related changes
Therapy-related myeloid neoplasms
AML, NOS (not otherwise specified)
Myeloid sarcoma

B. Old FAB Classification (still used descriptively):

FAB	Type	Blast Cell
M0	Minimally differentiated AML	Undifferentiated blasts
M1	AML without maturation	Myeloblasts (>90%)
M2	AML with maturation	Myeloblasts + promyelocytes; t(8;21)
M3	Acute promyelocytic leukemia (APL)	Promyelocytes with Auer rods, DIC; t(15;17)
M4	Acute myelomonocytic leukemia	Myeloid + monocytic; inv(16)
M5	Acute monocytic leukemia	Monocytes/monoblasts
M6	Erythroleukemia	Erythroid + myeloid blasts
M7	Megakaryoblastic leukemia	Megakaryoblasts; Down syndrome association

Key diagnostic criterion: Blasts ≥20% of bone marrow cellularity (WHO), except for certain genetic subtypes where diagnosis is made regardless of blast count.

VSAQ 4 - Reed-Sternberg (RS) Cell

The Reed-Sternberg cell is the pathognomonic (diagnostic) cell of Hodgkin Lymphoma.

Morphology:

Very large cell: 15-45 µm in diameter
Enormous multilobate nucleus (often bilobed or binucleate)
Exceptionally prominent nucleoli - large, eosinophilic/acidophilic, inclusion-like, surrounded by a clear halo/zone
Classic "owl-eye" appearance - the two nuclear lobes with their prominent nucleoli resemble owl eyes
Abundant, slightly eosinophilic cytoplasm

Immunophenotype:

CD15+ (Lewis blood group antigen; myelomonocytic marker)
CD30+ (Ki-1 antigen; activation marker; also expressed in anaplastic large cell lymphoma)
CD45- (leukocyte common antigen - negative, unlike most lymphomas)
CD20- (B-cell marker - negative in classic HL; positive in nodular lymphocyte-predominant HL variant)
PAX5+ (weak; transcription factor indicating B-cell origin despite loss of mature B-cell markers)

RS Cell Variants:

Lacunar cell (nodular sclerosis): Single multilobate nucleus; cytoplasm retracts in formalin → "lacuna" (empty space)
Lymphocytic-histiocytic (L&H) / "Popcorn" cell (nodular lymphocyte-predominant HL): Multilobated nucleus resembling popcorn; CD20+, CD30-, CD15-
Mononuclear RS variant ("Hodgkin cell"): Single nucleus with prominent nucleolus
Pleomorphic RS cell (lymphocyte depletion): Bizarre, highly pleomorphic

Origin: Germinal center B cells (proven by microdissection showing identical somatic hypermutated Ig gene rearrangements in all RS cells of a given case).

VSAQ 5 - Hemolytic vs Non-Hemolytic Anemia

Feature	Hemolytic Anemia	Non-Hemolytic Anemia
Mechanism	Accelerated RBC destruction (lifespan <120 days)	Decreased production, nutritional deficiency, or blood loss
Reticulocyte count	↑↑ (hyperregenerative; bone marrow response)	Normal or ↓ (hyporegenerative)
Bilirubin	↑ Unconjugated (indirect)	Normal
Jaundice	Common (lemon-yellow tinge)	Usually absent
Spleen	Splenomegaly (extravascular hemolysis)	Usually not enlarged
Haptoglobin	↓ (consumed binding free Hb)	Normal
LDH	↑ (released from lysed RBCs)	Normal (unless megaloblastic)
Coombs test	Positive (immune) / Negative (non-immune)	Negative
Bone marrow	Erythroid hyperplasia (M:E ratio reversed)	Variable: hypoplastic (aplastic), megaloblastic, or iron-depleted
Hemoglobinuria	May be present (intravascular)	Absent
MCV	Usually normocytic (can be high due to reticulocytes)	Microcytic (IDA/thalassemia) or macrocytic (B12/folate)
Examples	Hereditary spherocytosis, G6PD, AIHA, sickle cell, TTP	IDA, megaloblastic, aplastic anemia, ACD
Peripheral smear	Spherocytes, schistocytes, sickle cells, polychromasia	Microcytes, macroovalocytes, hypersegmented neutrophils
Gallstones	Pigment stones (bilirubin stones) in chronic cases	Not a feature

Sources: Robbins & Kumar Basic Pathology (Robbins Pathology), 9780323790185; Guyton and Hall Textbook of Medical Physiology, 9780443111013; Henry's Clinical Diagnosis and Management by Laboratory Methods, 9780323673204

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