SMPD1 and lysosomal storage disease: Acid sphingomyelinase deficiency (ASMD) or Niemann-Pick type A/B (OMIM#257,220, and 607,616, respectively) is a lysosomal disorder caused by the deficiency of acid sphingomyelinase (ASM) due to pathogenic variants in the SMPD1 gene [1–4].