To the Editor: with PNH3-6 and some reports of patients with more than one coexistent PNH clone. 7, 8 The majority of PIG-A mutations are small insertions or deletions that result in a frame-shift and early termination Paroxysmal nocturnal hemoglobinuria (PNH) is due to a somatic of the PIG-A product. In all of these cases there is no active PIG-mutation of the PIG-A gene occurring in a hematopoietic stem cell. A protein and thus a complete deficiency of GPI-linked proteins. In This results in a deficiency of all proteins that are normally attached a minority of patients with PNH, the PIG-A mutation is a point to the cell membrane via a glycosyl phosphatidylinositol (GPI) an- mutation resulting in an amino acid substitution within the PIG-A chor. 1, 2 There have been many reports of PIG-A mutations in patients protein. In these cases, a normal length PIG-A protein is produced