Cerebrotendinous xanthomatosis: treatments with simvastatin, lovastatin, and chenodeoxycholic acid in 3 siblings. We report 3 sisters treated for cerebrotendinous xanthomatosis. We treated one, with a severe neurologic form of the illness, with chenodeoxycholic acid, then lovastatin and simvastatin. These drugs had different efficacy and tolerance, but induced no clinical improvement. Her sisters, without neurologic symptoms, received chenodeoxycholic acid, which normalized the cholestanol level. Optimal treatment of this illness must begin before there is significant clinical symptomatology. 