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Anemia — Topics 53–66: Comprehensive Review

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53. Modern Classification of Anemia

By Pathogenesis:

1. Anemias due to blood loss (hemorrhagic)
   • Acute post-hemorrhagic
   • Chronic post-hemorrhagic (→ iron deficiency)
2. Anemias due to impaired RBC production (dyserythropoietic)
   • Nutritional deficiency: Fe, B12, folate
   • Bone marrow failure: aplastic, hypoplastic
   • Bone marrow infiltration: leukemia, myeloma, metastases
   • Chronic disease anemia (ACD)
   • Renal anemia (↓ EPO)
3. Anemias due to increased RBC destruction (hemolytic)
   • Congenital (corpuscular defects)
   • Acquired

By MCV (Morphological Classification):

By Severity (Hb level):

By Bone Marrow Response:

• Regenerative: elevated reticulocytes (hemolytic, blood loss)
• Hypo/Aregenerative: normal or low reticulocytes (aplastic, nutritional deficiency)

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54. Etiological Factors Contributing to Anemic Syndrome

General mechanisms:

1. Blood loss — GI bleeding (ulcer, cancer, hemorrhoids), menorrhagia, trauma, surgery, parasitosis (hookworm)
2. Nutritional deficiencies
   • Iron: poor intake, malabsorption (celiac, gastrectomy), increased demand (pregnancy, growth)
   • B12: strict vegetarianism, pernicious anemia (anti-intrinsic factor Ab), gastric atrophy, terminal ileum disease (Crohn's), fish tapeworm
   • Folate: poor diet (alcoholics, elderly), pregnancy, malabsorption, drugs (methotrexate, phenytoin, trimethoprim)
3. Bone marrow suppression
   • Drugs/toxins: chloramphenicol, benzene, cytostatics, radiation
   • Viruses: EBV, CMV, hepatitis (seronegative aplastic)
   • Autoimmune destruction of stem cells
4. Hemolysis
   • Intrinsic RBC defects (hereditary)
   • Extrinsic factors (autoimmune, microangiopathic, infections, drugs)
5. Chronic disease: inflammation → hepcidin ↑ → iron sequestration
6. Renal failure: ↓ EPO production
7. Endocrine causes: hypothyroidism, adrenal insufficiency
8. Bone marrow infiltration: leukemia, lymphoma, myeloma, myelofibrosis, metastases

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55. Classification of Hemolytic Anemias

I. Congenital (Hereditary) — Corpuscular Defects

• Hereditary spherocytosis (↓ spectrin, ankyrin) — AD
• Hereditary elliptocytosis
• Hereditary stomatocytosis

• G6PD deficiency (X-linked) — oxidative hemolysis triggered by infections, drugs (primaquine, dapsone), fava beans
• Pyruvate kinase deficiency (AR) — chronic non-spherocytic hemolytic anemia

• Structural: Sickle cell disease (HbS), HbC, HbE
• Synthesis: α-thalassemia, β-thalassemia

II. Acquired — Extra-corpuscular Defects

• Autoimmune hemolytic anemia (AIHA):
  • Warm type (IgG): idiopathic, SLE, CLL, drugs (methyldopa, penicillin)
  • Cold type (IgM): cold agglutinin disease (Mycoplasma, EBV), paroxysmal cold hemoglobinuria
• Alloimmune: hemolytic transfusion reaction, HDN (Rh/ABO incompatibility)
• Drug-induced

• Microangiopathic: TTP, HUS, DIC, mechanical heart valves
• Infections: malaria (Plasmodium), Clostridium, Babesia
• Chemical/physical: lead toxicity, burns, oxidants
• Hypersplenism
• Paroxysmal nocturnal hemoglobinuria (PNH) — clonal, acquired GPI-anchor defect → complement-mediated lysis

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56. Diagnostic Criteria for Iron Deficiency Anemia (IDA)

Stages of Iron Deficiency:

1. Pre-latent: depleted iron stores (↓ ferritin), no anemia
2. Latent: ↓ serum iron, ↑ TIBC, no anemia yet
3. Manifest IDA: anemia with all peripheral changes

Laboratory Criteria:

Clinical Features (sideropenic syndrome):

• Fatigue, pallor, dyspnea on exertion
• Pica (craving for ice/clay/dirt), glossitis, angular stomatitis, dysphagia (Plummer-Vinson syndrome)
• Koilonychia (spoon nails), brittle hair/nails
• Tachycardia, systolic flow murmur

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57. Diagnostic Criteria for B12 and Folate Deficiency Anemia

Common Features (Megaloblastic Anemia):

Distinguishing B12 from Folate Deficiency:

Key: Neurological involvement (subacute combined degeneration) occurs only in B12 deficiency — treating folate deficiency with folate can mask B12 deficiency and worsen neurological damage.

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58. Diagnostic Criteria for Hypo- and Aplastic Anemia

Definition:

• Aplastic anemia: pancytopenia + hypocellular bone marrow (<25% cellularity) due to destruction/suppression of pluripotent stem cells

Severity Classification (Camitta Criteria):

Laboratory Findings:

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59. Diagnostic Criteria for Hemolytic Anemia

General Evidence of Hemolysis:

• ↑ Indirect (unconjugated) bilirubin → jaundice
• ↑ LDH (released from lysed RBCs)
• ↓ Haptoglobin (binds free Hb; absent in intravascular hemolysis)
• Hemoglobinemia, hemoglobinuria, hemosiderinuria (intravascular)
• Urobilinogen ↑ in urine/feces

• ↑ Reticulocytes (reticulocytosis >2–3%) — key marker
• Polychromasia on blood film
• Bone marrow: erythroid hyperplasia (M:E ratio ↓ to 1:1 or reversed)
• Extramedullary hematopoiesis in severe chronic cases

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60. Differential Diagnosis: Hypo-Aplastic Anemia vs. Leukemia

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61. Laboratory Indicators for Hypo- and Aplastic Anemia

Peripheral Blood:

• Pancytopenia: Hb ↓, WBC ↓ (especially neutrophils), platelets ↓
• Reticulocytes ↓ or absent (critical — aregenerative anemia)
• Normochromic normocytic anemia (MCV may be mildly elevated due to macrocytosis)
• No blasts, no immature WBCs, no dysplastic cells
• RDW may be normal

Biochemistry:

• Serum iron ↑, ferritin ↑ (iron not utilized)
• TIBC normal or ↓
• Erythropoietin (EPO) ↑ (compensatory)
• B12/folate: normal (to exclude megaloblastic cause)
• LDH: normal or mildly elevated

Bone Marrow (Definitive):

• Aspirate: hypocellular, abundant fat cells, few hematopoietic precursors, no blasts
• Trephine biopsy (gold standard): cellularity <25–30%, fatty replacement; presence of lymphocytes, plasma cells, mast cells in residual stroma
• No fibrosis (distinguishes from myelofibrosis)

Special Tests:

• Chromosomal breakage analysis (DEB/MMC test) — to exclude Fanconi anemia (especially in young patients)
• PNH clone by flow cytometry — up to 50% of AA cases have small PNH clone
• Telomere length assay — telomeropathy syndromes (dyskeratosis congenita)

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62. Methods of Bone Marrow Examination

1. Bone Marrow Aspiration (BMA)

• Site: posterior superior iliac spine (most common), anterior iliac spine, sternum (less preferred)
• Technique: Jamshidi or Illinois needle; aspiration of 0.5–1.5 mL
• Yields: smears for cytology, differential count, cytochemistry, immunophenotyping, cytogenetics, molecular studies
• Limitations: cannot assess cellularity or architecture; "dry tap" in fibrosis or hypercellular marrow

2. Bone Marrow Trephine Biopsy

• Site: posterior iliac crest (preferred)
• Core: 2 cm minimum length
• Yields: histological sections for cellularity, architecture, fibrosis (reticulin stain), infiltrates
• Essential for: aplastic anemia (cellularity), myelofibrosis, granulomas, lymphoma staging
• Stains: H&E, Giemsa, Prussian blue (iron), reticulin, PAS

3. Bone Marrow Studies Performed:

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63. Diagnosis and Principles of Treatment of Iron Deficiency Anemia

Diagnosis:

1. Confirm IDA: CBC + peripheral smear + ferritin + serum iron + TIBC
2. Identify the cause: stool OB, upper/lower GI endoscopy, menstrual history, dietary assessment, malabsorption workup

Treatment Principles:

• Ferrous sulfate 325 mg (65 mg elemental Fe) TID — standard
• Take on empty stomach (↑ absorption); vitamin C (ascorbic acid) enhances absorption
• Avoid with: tea, coffee, milk, antacids, PPIs, calcium (all ↓ absorption)
• Duration: continue 3–6 months after Hb normalizes to replenish stores
• Expected response: reticulocytosis at day 5–10; Hb rises ~1–2 g/dL per week; Hb normalizes in 4–8 weeks

• Intolerance of oral iron
• Malabsorption (celiac, post-gastrectomy, IBD)
• Non-compliance
• Need for rapid repletion (pre-surgery, renal anemia on EPO)
• Agents: ferric carboxymaltose, iron sucrose, low molecular weight iron dextran, ferumoxytol

• Only if severe symptomatic anemia (Hb <70 g/L) or hemodynamic compromise
• Not for correction of iron stores

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64. Iron-Containing Drugs: Indications and Contraindications

Oral Iron Preparations:

Parenteral Iron Preparations:

Indications:

• Iron deficiency anemia (all causes)
• Prevention: pregnancy, prematurity, exclusively breastfed infants
• Pre-operative optimization (before elective surgery)
• Anemia of CKD on EPO therapy (functional iron deficiency)
• Heart failure with iron deficiency (even without anemia — FAIR-HF, AFFIRM-AHF trials)

Contraindications:

• Hemolytic anemia (worsens iron overload)
• Hemochromatosis / hemosiderosis (iron overload)
• Iron-loading anemias: sideroblastic anemia, thalassemia (without confirmed IDA)
• Acute infections (iron promotes bacterial growth; hold IV iron during active infection)
• Known hypersensitivity (especially IV iron dextran)
• Non-iron deficiency anemias (B12, folate, aplastic — no benefit, may harm)
• Anemia of chronic disease without true iron deficiency (ferritin >100 μg/L without low transferrin saturation)

Side Effects:

• Oral: GI upset, nausea, constipation, black stools, metallic taste
• IV: flushing, hypotension, anaphylaxis (rare but serious, especially with high-MW dextran), DILI

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65. Diagnosis and Principles of Treatment of B12 and Folate Deficiency Anemia

Diagnosis:

1. CBC + film → macrocytic anemia, hypersegmented neutrophils
2. Serum B12, serum/RBC folate
3. If B12 low: MMA, homocysteine, anti-intrinsic factor Ab, anti-parietal cell Ab
4. Schilling test (historical; rarely used now)
5. Endoscopy if gastric atrophy suspected; terminal ileum imaging if Crohn's suspected

Treatment of B12 Deficiency:

• Hydroxocobalamin (preferred) or cyanocobalamin IM:
  • Induction: 1000 μg IM daily × 7 days, then weekly × 4 weeks
  • Maintenance: 1000 μg IM every 3 months (lifelong)
• Oral B12 (cyanocobalamin 1000–2000 μg/day): effective even without IF via passive diffusion — option in dietary deficiency or patient preference

• Reticulocytosis peak at day 5–7
• Hb normalizes in 6–8 weeks
• Neurological improvement may take months; may be irreversible if delayed

Critical: Always rule out B12 deficiency before treating with folate alone — folate can correct the anemia but will not prevent/may worsen subacute combined degeneration.

Treatment of Folate Deficiency:

• Folic acid 5 mg/day orally × 4 months (or longer if ongoing need)
• Dietary improvement (leafy greens, legumes, citrus)
• Prevention: folic acid 0.4–0.5 mg/day in women planning pregnancy; 5 mg/day if prior neural tube defect
• Drug-induced (methotrexate): folinic acid (leucovorin) rescue — does NOT interfere with methotrexate's antifolate mechanism

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66. Diagnosis and Principles of Treatment of Hemolytic Anemia

Diagnosis:

1. Confirm hemolysis: reticulocytosis + ↑ LDH + ↓ haptoglobin + ↑ indirect bilirubin
2. Site: intravascular (hemoglobinuria, hemoglobinemia) vs. extravascular (splenomegaly)
3. Cause:
   • DAT positive → immune-mediated
   • DAT negative → non-immune (enzyme assay, osmotic fragility, Hb electrophoresis, flow cytometry for PNH, film for schistocytes)

Treatment by Type:

Autoimmune Hemolytic Anemia (AIHA) — Warm Type:

• 1st line: Prednisolone 1 mg/kg/day → taper over weeks/months
• 2nd line: Rituximab (anti-CD20) — 375 mg/m² × 4 doses
• Refractory: Splenectomy (removes site of destruction)
• Supportive: Folate supplementation; transfuse only if life-threatening (crossmatch difficult)

AIHA — Cold Type:

• Avoid cold exposure
• Rituximab (more effective than steroids in cold AIHA)
• Plasmapheresis in severe/acute cases
• Steroids generally less effective

Hereditary Spherocytosis:

• Folate supplementation
• Splenectomy: curative for anemia (removes site of destruction) — defer until age 6+ to preserve immunity; vaccinate against encapsulated organisms (pneumococcus, meningococcus, Hib) before splenectomy

G6PD Deficiency:

• Avoid triggers: oxidant drugs, fava beans, infections
• Supportive care during acute crisis; transfusion if severe

Sickle Cell Disease:

• Hydroxyurea (↑ HbF production → ↓ sickling)
• Prophylactic penicillin V (children) + vaccinations
• Folic acid supplementation
• Voxelotor (stabilizes HbS oxygenated form), crizanlizumab (anti-P-selectin)
• Transfusion / exchange transfusion in acute chest syndrome, stroke
• Allogeneic HSCT: potentially curative; gene therapy emerging

Thalassemia Major:

• Regular blood transfusions (maintain Hb >90–100 g/L)
• Iron chelation (desferrioxamine, deferasirox, deferiprone) to prevent hemosiderosis
• Allogeneic HSCT: curative option
• Luspatercept (erythroid maturation agent) for β-thalassemia

PNH:

• Eculizumab (anti-C5 monoclonal Ab) — prevents complement-mediated lysis; dramatically reduces hemolysis, thrombosis
• Ravulizumab (longer-acting anti-C5)
• Anticoagulation if thrombosis present
• Allogeneic HSCT for severe cases with aplasia

Microangiopathic (TTP):

• Plasma exchange (PEX) with FFP — first-line emergency treatment
• Corticosteroids + rituximab
• Caplacizumab (anti-VWF) for acute TTP

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