SMPD1 and Niemann-Pick disease: LSDs include Farber’s disease, caused by the dysfunction of aCDase; Krabbe’s disease (Globoid leukodystrophy), caused by the absence of galactosylceramidase (GalCer/3-galactosidase); Gaucher’s disease due to the absence of glucosylceramidase (GlcCer/3-glucosidase) and Niemann–Pick disease (NP) characterized by the absence of aSMase.