Sphingomyelin levels, along with those of cholesterol, are increased in the kidney of Niemann-Pick disease, a genetic disorder due to mutations in NPC1/NPC2 (encoding intracellular cholesterol transporters) and SMPD1 (encoding an acid sphingomyelinase) genes, the latter associated with proteinuria [16]. Here, SMPD1 is linked to Niemann-Pick disease.