NPC2 and Niemann-Pick disease type C: 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).