Paroxysmal nocturnal hemoglobinuria 1

Paroxysmal nocturnal hemoglobinuria (PNH) is an uncommon acquired hemolytic anemia that often manifests with hemoglobinuria, abdominal pain, smooth muscle dystonias, fatigue, and thrombosis. The disease results from the expansion of hematopoietic stem cells harboring a mutation in the PIGA gene, which encodes a protein required for the biosynthesis of glycosylphosphatidylinositol (GPI), a lipid moiety that attaches dozens of proteins to the cell surface. Thus, PNH cells are deficient in cell surface GPI-anchored proteins. This deficiency on erythrocytes leads to intravascular hemolysis, since certain GPI-anchored proteins (i.e., CD55 (125240) and CD59 (107271)) normally function as complement regulators. Free hemoglobin released from intravascular hemolysis leads to circulating nitrous oxide depletion and is responsible for many of the clinical manifestations of PNH, including fatigue, erectile dysfunction, esophageal spasm, and thrombosis (review by Brodsky, 2008). Genetic Heterogeneity of Paroxysmal Nocturnal Hemoglobinuria See also PNH2 (615399), which may be caused by germline and somatic mutation in the PIGT gene (610272) on chromosome 20q13. [from OMIM]