This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General pathology, Subject name: Pathology
Paroxysmal nocturnal hemoglobinuria results from acquired mutations in 
Select and explain. 
A. PML-RARA, B. BCL-2, C. NOTCH1, D. PIGA
D: PIGA
Answer: D: PIGA 
Explanation: Paroxysmal nocturnal hemoglobinuria (PNH) is a disease that results from acquired mutations in the phosphatidylinositol glycan complementation group A gene (PIGA), an enzyme that is essential for the synthesis of ceain membrane-associated complement regulatory proteins.PNH blood cells are deficient in three GPI-linked proteins that regulate complement activity: (1) decay accelerating factor, or CD55; (2) membrane inhibitor of reactive lysis, or CD59; and (3) C8 binding protein.Of these factors, the most impoant is CD59, a potent inhibitor of C3 convease that prevents the spontaneous activation of the alternative complement pathway.Red cells deficient in these GPI-linked factors are abnormally susceptible to lysis or injury by complement and manifests as intravascular hemolysisRobbins pathology 9e pg: 642