A 30-year-old man presents with episodic dark urine, haemolytic anaemia, and thrombocytopenia. He reports the haemolytic episodes are worse in the morning. Flow cytometry of peripheral blood shows absent CD55 and CD59 on red blood cells and granulocytes. The treatment that addresses the underlying complement dysregulation is:
- A Eculizumab (anti-C5 monoclonal antibody) ✓
- B Prednisolone
- C Splenectomy
- D Danazol
Explanation
Paroxysmal nocturnal haemoglobinuria (PNH) is caused by a somatic mutation in PIG-A gene leading to deficiency of GPI-anchored complement regulatory proteins CD55 (DAF) and CD59 (MIRL), resulting in uncontrolled complement-mediated haemolysis. Eculizumab, a humanised anti-C5 monoclonal antibody, blocks terminal complement activation and dramatically reduces haemolysis, thrombosis, and transfusion requirements; ravulizumab (long-acting anti-C5) and iptacopan (factor B inhibitor) are newer options. Prednisolone is not effective. Splenectomy does not address complement-mediated intravascular haemolysis. Danazol is used in aplastic anaemia, not PNH.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.