CD 59 deficiency leads to:-

PNH: - D/t acquired mutations in phosphatidyl inositol glycan complementation group A gene (PIGA), an enzyme essential for synthesis of ceain membrane-associated complement regulatory proteins. - 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; C8 binding protein. - It results in complement activation abnormally resulting in - destruction of RBC, WBC, platelets - Pancytopenia - PNH is diagnosed by Flaer flow cytometry, which provides a sensitive means for detecting red cells that are deficient in GPI-linked proteins such as CD59.