Similarly, TMS revealed cortico-spinal alterations even in subjects with mild clinical signs of cortico-spinal tract involvement in cerebrotendinous xanthomatosis (a rare neurometabolic disease due to defective activity of sterol 27-hydroxylase, with plasma and tissue cholestanol storage) (Mignarri et al., 2011), the clinical phenotype of which is characterized by both systemic manifestations and neurological signs, including cognitive decline. The gene discussed is CYP27A1; the disease is Mental deterioration.