[PNH--paroxysmal nocturnal hemoglobinuria. An old disease explained by new technology]

The review outlines developments in research on paroxysmal nocturnal haemoglobinuria (PNH). The disease is due to a somatic mutation of the PIG-A gene. This results in deficiency of the protein, GPI (glucosyl phosphatidyl inositol), which serves as an anchor for several membrane-bound proteins including MIRL (CD59; membrane inhibitor of reactive lysis) and DAF (CD55; decay accelerating factor). The absence of these proteins results in increased cellular sensitivity to complement-mediated lysis, affecting not only red cells, leukocytes and platelets, but also haemopoietic stem cells. This explains the often complex clinical picture in PNH (haemolysis, pancytopenia and increased thrombotic predisposition), and the well known relationship between PNH and aplastic anaemia.