PIGA and paroxysmal nocturnal hemoglobinuria: Somatic PIGA mutations, and less commonly, phosphatidylinositol glycan anchor biosynthesis class B (PIGB) and T (PIGT) mutations, are responsible for paroxysmal nocturnal hemoglobinuria (PNH), a complement-driven acquired hemolytic anemia that often manifests as hemoglobinuria, abdominal pain, smooth muscle dystonia, fatigue, and thrombosis (4–6).