Paroxysmal nocturnal haemoglobinuria (PNH)
PNH is a rare clonal haemopoietic disorder characterised by bone marrow failure, chronic haemolytic anaemia with acute episodes and thrombosis. PNH can arise either spontaneously or can occur in the setting of another marrow disorder such as aplastic anaemia and myelodysplastic syndromes.
PNH is caused by a mutation in the PIG-A gene in haematopoietic stem cell that leads to disruption of Glyco phosphatidyl inositol (GPI) synthesis and a deficiency of GPI linked proteins. This results in the absence of GPI-linked complement inhibitors CD55 and CD59, resulting in increased susceptibility to complement-mediated haemolysis.
Iron replacement often leads to an increase in haemolysis.