NPC1 and lysosomal storage disease: Niemann-Pick type C (NPC) disease is a progressive lysosomal storage disorder with an estimated incidence of 1:100,000–120,000 among newborns (1, 2), caused by an autosomal recessive mutation in the NPC1 (95% of the cases; Online Mendelian Inheritance in Man no.: 257220) or NPC2 gene.