Paroxysmal nocturnal hemoglobinuria (PNH) is characterized by the presence of an acquired somatic mutation of the X‐linked PIGA (phosphatidylinositol glycan‐complementation class A) gene in hematopoietic stem cells, leading to the emergence of a clone lacking the glycosylphosphatidylinositol (GPI) anchor [1]. The gene discussed is PIGA; the disease is paroxysmal nocturnal hemoglobinuria.