Over the past 15 years, it has become clear that inborn errors of cholesterol synthesis give rise to human malformation/mental retardation syndromes. Smith-Lemli-Opitz syndrome is the prototypical example of a post-squalene inborn error of metabolism; however, this group of disorders now includes lathosterolosis, desmosterolosis, X-linked dominant chondrodysplasia (CDPX2), CHILD syndrome, HEM dysplasia, and some cases of Antley-Bixler syndrome (1-3). Due to the extremely rare occurrence of some of these disorders, the full phenotypic spectrum has yet to be defined. Cholesterol transport in cells can also cause a disorder known as Niemann-Pick Disease type C (NPC). NPC belongs to a group of disorders known as lysosomal storage disorders. The purpose of this protocol is to 1) allow for the collection of biomaterial and medical information that can be studied to gain insight into the pathological processes; 2) allow for the collection of DNA and medical information from individuals who have a phenotypic resemblance to known disorders of cholesterol synthesis, lysosomal storage disorders or individuals who may be carriers of these disorders.