Haemolytic Anaemia – Mechanisms, Classification & Autoimmune Causes (Exam-Ready Flashcards)

What is haemolysis?

Reduced red cell lifespan due to increased destruction, leading to anaemia that may be compensated or uncompensated.

What are the two mechanisms of haemolysis?

Extravascular – spleen/liver macrophages and Intravascular – destruction within circulation via complement

What characterises extravascular haemolysis?

Macrophage removal of antibody-coated red cells, spherocytes, ↑ bilirubin, splenomegaly, no haemoglobinuria.

What characterises intravascular haemolysis?

Complement-mediated lysis, haemoglobinaemia, haemoglobinuria, ↓ haptoglobin, risk of renal damage.

What is Autoimmune Haemolytic Anaemia (AIHA)?

Anaemia caused by autoantibodies directed against the patient’s own red cell antigens.

How is AIHA diagnosed?

Positive Direct Antiglobulin Test (DAT / DCT) showing IgG and/or complement on red cells.

What are the two main types of AIHA?

Warm AIHA(IgG) Cold AIHA(IgM with complement)

Common clinical features of haemolysis?

Pallor, fatigue, jaundice, splenomegaly, dark urine, gallstones.

Key laboratory features of haemolysis?

increase LDH, ↑ unconjugated bilirubin, ↓ haptoglobin, ↑ reticulocytes, polychromasia/NRBCs.

Warm AIHA – mechanism

IgG (± C3d) binds red cells at 37°C → splenic macrophage removal → extravascular haemolysis.

Warm AIHA – diagnosis & blood film

DAT positive for IgG ± C3d, spherocytes on film, anaemia of variable severity.

Warm AIHA – treatment

Steroids (first line), rituximab, splenectomy, immunosuppression, folic acid, transfusion if severe.

Cold AIHA – mechanism

IgM binds red cells in cold periphery → complement activation → intra ± extravascular haemolysis.

Cold AIHA – diagnosis & lab clues

DAT C3d positive only, red cell agglutination, spurious ↑ MCV/MCHC, mild–moderate anaemia.

Cold AIHA – treatment

Keep warm, rituximab, complement inhibitors (eculizumab), plasmapheresis, cautious transfusion with blood warmer.

Paroxysmal Cold Haemoglobinuria (PCH)

Acute severe intravascular haemolysis due to Donath–Landsteiner IgG; DAT complement positive; supportive management.