Increasing endolysosomal cholesterol levels in Niemann-Pick disease type C, caused by an inherited defect of a steroid transfer protein, either NPC2 or NPC1, are accompanied by an accumulation of SM (61), glycosphingolipids (62, 63), sphingosine (64), and the anionic endolysosomal marker phospholipid, BMP (65, 66). This evidence concerns the gene NPC1 and Niemann-Pick disease type C.