Niemann-Pick disease (NPD) is an eponym that refers to two distinct metabolic abnormalities including the deficiency of acid sphingomyelinase (ASM) enzyme [NPD types A, A/B and B; collectively called as ASM deficiency (ASMD)] and the defective function in cholesterol transport (NPD type C) (1–3). The gene discussed is SMPD1; the disease is Niemann-Pick disease.