Our finding that CD is beneficial in reducing cholesterol and GSLs in neurons lacking either NPC1 or NPC2 proteins, but not in neurons in GM1 gangliosidosis or MPS IIIA, may be revealing of the importance of cholesterol's mobility in the NPC-affected cell compared with other lysosomal diseases. The gene discussed is NPC2; the disease is mucopolysaccharidosis type 3A.