NPC1 and Niemann-Pick disease type C: Niemann-Pick disease type C (NPC) is a neurovisceral lysosomal lipid storage disease caused by autosomal recessive mutations in either the NPC1 (95% of patients) or NPC2 genes leading to deficiency of NPC1 or NPC2.1, 2, 3 NPC is a lipid trafficking disorder, characterised by the accumulation of unesterified cholesterol, glycosphingolipids (GSLs), sphingosine and sphingomyelin, within the late endosome/lysosome.3