NPC1 and nervous system disorder: The aim of the present work stemmed from the evidence that heterozygous carriers of NPC1 gene mutations, which historically have been considered as clinically unaffected, occasionally develop neurological disorders such as extrapyramidal syndromes or dementia.19, 20, 21, 33 Thus, it might be postulated that either the neurological disorder and the heterozygous NPC1 mutation occur independently, or that the heterozygous NPC1 gene mutation might confer susceptibility to the development of a neurological disorders.