Cerebrotendinous xanthomatosis (CTX; McKusick 213700) is a rare autosomal recessive inborn error of metabolism involving the mitochondrial 26-hydroxylation of the sterol side-chain in bile acid synthesis (Bjorkhem and Skrede 1989). Generally, patients with CTX are diagnosed in their third decade or later, symptoms appearing in or after the second decade. Cataracts, tendon xanthomas and neurological signs and symptoms (low intelligence, pyramidal signs, cerebellar signs) are considered to be the key clinical features of the disease (Kuriyama et al 1991)