Cerebrotendinous xanthomatosis.

Cerebrotendinous xanthomatosis is a rare familial lipid storage that is caused by a defect in bile acid synthesis. As a result, large amounts of cholestanol, the 5 alpha-dihydro derivative of cholesterol, accumulate in virtually every tissue, with extra large deposits in the nervous system, xanthomas, and bile. Clinically, progressive neurologic dysfunction, tendon xanthomas, cataracts, and atherosclerosis are commonly found. Because chenodeoxycholic acid, a primary bile acid, is almost devoid from the bile, replacement therapy (750 mg per day) suppresses abnormal bile acid synthesis, reduces elevated cholestanol synthesis and plasma concentrations, and improves neurologic function in this disease.