A 42-year-old man presents with haemolytic anaemia, Coombs-negative (direct antiglobulin test negative), episodes of dark urine especially in the morning, and flow cytometry showing absence of CD55 and CD59 on red cell surface. What complication is he at highest risk of, and what is the current treatment?
- A Aplastic crisis; erythropoietin
- B Acute kidney injury; fresh frozen plasma
- C Cerebral venous thrombosis; antiplatelet therapy only
- D Thrombosis; eculizumab (anti-C5 complement inhibitor) ✓
Explanation
The clinical features of Coombs-negative haemolysis with haemoglobinuria and absence of GPI-anchored proteins CD55 (DAF) and CD59 (protectin) on flow cytometry confirm paroxysmal nocturnal haemoglobinuria (PNH). The most dangerous complication is thrombosis (portal, hepatic, cerebral veins), responsible for most PNH mortality. Eculizumab, a monoclonal anti-C5 complement inhibitor, dramatically reduces haemolysis, transfusion requirements, and thrombotic events. Ravulizumab (long-acting anti-C5) is an alternative with less frequent dosing. Anticoagulation alone is insufficient and EPO does not address complement-mediated haemolysis.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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