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PNH — RACP Adult Medicine MCQ

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HardHaematologyPNHRACP Adult Medicine

A 35-year-old man presents with episodes of dark urine (especially morning), fatigue, and abdominal pain. He has a history of DVT. FBE shows pancytopenia with Hb 85 g/L. LDH is elevated and haptoglobin is low. DAT is negative. Flow cytometry shows absence of CD55 and CD59 on red cells and granulocytes. What is the most likely diagnosis?

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Correct answer: B — Paroxysmal nocturnal haemoglobinuria

DAT-negative intravascular haemolysis with pancytopenia, thrombosis, and absent GPI-anchored proteins (CD55, CD59) on flow cytometry is diagnostic of PNH. It is caused by somatic PIGA mutation leading to complement-mediated haemolysis. Treatment is complement inhibition (eculizumab or ravulizumab). Anticoagulation for thrombosis. Meningococcal vaccination is mandatory before complement therapy.

Reference: BSH – 2024 – PNH Guidelines; ICCS PNH Consensus 2023