<prompt> CD59 marker deficiency leads to which of the following disease?PNHPTENBRRCowden syndrome  <response>: Ans. a. Paroxysmal nocturnal hemoglobinuria PNHRef: Robbins and Cotran Pathologic Basis of Disease 9th Ed; Page No-642Paroxysmal Nocturnal HemoglobinuriaIncreases complement-mediated intravascular RBC lysis impaired synthesis of GPI anchor for decay-accelerating factor that protects RBC membrane from complement.Acquired mutation in a hematopoietic stem cell.Increases incidence of acute leukemias.Patients may report red or pink urine from hemoglobinuria.Associated with aplastic anemia.Triad: Coombs ? hemolytic anemia, pancytopenia, and venous thrombosis.Labs: CD5559 ? RBCs on flow cytometry.PNH blood cells are deficient in three GPI-linked proteins that regulate complement activity:Decay accelerating factor, or CD55;Membrane inhibitor of reactive lysis, or CD59; andC8 binding protein.The most important is CD59, a potent inhibitor of C3 convertase that prevents the spontaneous activation of the alternative complement pathwayTreatment: Eculizumab terminal complement inhibitor. 