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.