An autosomal recessive lipid storage disorder that is characterized by accumulation of CHOLESTEROL and SPHINGOMYELINS in cells of the VISCERA and the CENTRAL NERVOUS SYSTEM. Type C (or C1) and type D are allelic disorders caused by mutation of gene (NPC1) encoding a protein that mediate intracellular cholesterol transport from lysosomes. Clinical signs include hepatosplenomegaly and chronic neurological symptoms. Type D is a variant in people with a Nova Scotia ancestry.