Paroxysmal nocturnal hemoglobinuria

Also know as PNH is an acquired complement-induced hemolytic anemia that is due to a mutation of phosphatidylinositol glycan A (PIGA) gene (on chromosone X) which is resposible for making the cell membrane protein anchoring molecule glycosylphosphatidylinositol (GPI). Notably the gene is on chromosome X but unlike X-linked germline mutations (e.g. hemophilia A) which almost exclusively involve males, this acquired mutation involves males and females equally. The diagnosis is made by flow cytometry and showing loss of CD55 (Complement decay accelerating factor) and CD59 (protectin which usually inhibits the complement membrane attack complex) on multiple blood cell types (RBCs and WBCs). These patients are also at an increased risk of thrombosis.