PA16.1-3 | Haemolytic Anaemia — Definition, Classification & Lab Markers — Summary & Reflection

REFLECT

Look again at the opening clinical vignette — the 19-year-old Tamil Nadu student with yellow eyes since childhood, dark urine during fevers, splenomegaly, reticulocytes 14%, spherocytes on smear, and a father who had pigment stones.

1. Using Axis 1 (intravascular vs extravascular): What type of haemolysis does this patient most likely have? What findings support your answer?
2. Using Axis 2 (hereditary vs acquired) and Axis 3 (intracorpuscular vs extracorpuscular): Where would you classify this patient's likely diagnosis?
3. The patient has jaundice but 'normal-coloured urine' (no haemoglobinuria). What does this tell you about bilirubin metabolism in this case?
4. What laboratory tests would you order next to confirm haemolysis and begin characterising the specific disorder?

Write out your reasoning — no single-line answers. The goal is to use all three classification axes and the lab-marker map simultaneously, as you would in a clinical case.

KEY TAKEAWAYS

Core concepts from this SDL:

1. Haemolysis = premature RBC destruction before 120 days. Haemolytic anaemia = haemolysis that outpaces marrow compensation. The marrow has a 6–8× reserve; compensated haemolytic states occur when this reserve is sufficient.

2. Three classification axes (use all three for any case):
• Site: Extravascular (spleen/liver macrophages — 80%) vs Intravascular (blood vessel lumen — 20%)
• Cause: Hereditary (intrinsic defect, usually lifelong) vs Acquired (extrinsic trigger, recent onset)
• Defect location: Intracorpuscular (membrane/enzyme/Hb) vs Extracorpuscular (immune/mechanical/toxic)

1. Clinical features: Anaemia + pre-hepatic jaundice (acholuric) + splenomegaly + pigment gallstones + leg ulcers. Acute: haemolytic crisis. Intercurrent: aplastic crisis (B19).

4. Lab marker map:
• Both types: ↑reticulocytes (hallmark of marrow response), ↑unconjugated bilirubin, ↑LDH, polychromasia + nRBCs on smear.
• Intravascular specifically: markedly ↓haptoglobin, haemoglobinuria, urinary haemosiderin, methaemalbuminaemia.
• Extravascular specifically: splenomegaly, mild haptoglobin drop, no haemoglobinuria.

1. Peripheral smear morphology directs you to the specific diagnosis: spherocytes (HS/AIHA), schistocytes (MAHA), sickle cells (SCD), bite cells (G6PD), target cells (HbC/thal).

1. SDL2 = hereditary causes (HS, G6PD, PKD, sickle, thal). SDL3 = acquired causes (AIHA, MAHA, PNH, malaria).