This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Biochemistry
Which of the following enzyme is deficient in Niemann pick disease? 
Select and explain. 
A. Sphingomyelinase, B. Hexosaminidase-A, C. Aryl sulfatase, D. Galactosidase-A
A: Sphingomyelinase
Answer: A: Sphingomyelinase 
Explanation: Niemann-Pick disease (NPD) is a lipid storage disorder that results from the deficiency of a lysosomal enzyme, acid sphingomyelinase. The enzymatic defect results in pathologic accumulation of sphingomyelin (which is a ceramide phospholipid) and other lipids in the monocyte-macrophage system. Systemic involvement includes progressive lung disease, hepatosplenomegaly, sho stature, and pancytopenia. Ref: Clinical Studies in Medical Biochemistry Edited By Robe H. Glew, Miriam D. Rosenthal, 2006, Page 192; Lehninger Principles of Biochemistry, 4th Edition, Page 356