Acid sphingomyelinase deficiency (ASMD) is a rare lysosomal storage disorder that leads to the accumulation of sphingomyelin (and other lipids) in cells and tissues due to deficient acid sphingomyelinase activity (ASM, SMPD1; EC 3.1.4.12) [1]. The gene discussed is SMPD1; the disease is lysosomal storage disease.