Paroxysmal nocturnal hemoglobinuria. A complement-mediated disease.

Paroxysmal nocturnal hemoglobinuria (PNH) is a hemolytic disease characterized by an increased sensitivity of erythrocytes to the hemolytic action of complement. Two membrane proteins, the decay-accelerating factor and the C8-binding protein, which protect normal erythrocytes from the hemolytic action of complement, are deficient on the abnormal blood cells from patients with PNH. Other membrane proteins unrelated to complement regulation, but which share with the decay-accelerating factor and the C8-binding protein a common post-translational modification, namely a glycan-phosphatidylinositol linkage to the cell membrane, are also missing from PNH cells. In the present review, clinical, biological, and molecular aspects of PNH are discussed. In addition, diagnostic tests in clinical use are discussed, and new tests using indirect immunofluorescent assays are proposed.