Cerebrotendinous xanthomatosis is a rare autosomal recessive disorder of the bile acid synthesis pathway caused by deficiency of the enzyme sterol 27-hydroxylase (Cyp27A1) resulting in the production of bile alcohols, increased serum levels of the cholesterol oxidation product 7α-hydroxycholesterol and the cholesterol metabolite 5α-cholestan-3β-ol, and accelerated whole-body cholesterol synthesis. The most important clinical signs are juvenile cataract, childhood diarrhea, mental retardation, cerebellar ataxia, spasticity, dementia, epilepsy, peripheral neuropathy, tendon xanthomas, and premature arteriosclerosis with slowly progressive neurological dysfunction in the second or third decade.1 Early diagnosis is of the utmost importance because patients benefit from pharmacological therapy.2 However, although treatment with bile acid supplementation may improve neurological signs and symptoms, it does not completely reverse them.