We searched MEDLINE, Gene Ontology and OMIM databases to identify links to known pathways in ALS pathogenesis for CYP27A1. The CYP27A1 gene is involved in cholesterol metabolism and has been associated with cerebrotendinous xanthomatosis (CTX), which can present with progressive upper motor neuron signs and is a known clinical mimic for primary lateral sclerosis [39], [40]. The gene discussed is CYP27A1; the disease is cerebrotendinous xanthomatosis.