Ataxia due to Cerebrotendinous xanthomatosis

**Definition:** Ataxia in the setting of cerebrotendinous xanthomatosis, a rare autosomal recessive disorder of bile acid metabolism caused by a mutation in the CYP27A1 gene encoding mitochondrial enzyme sterol 27-hydroxylase. Accumulation of sterols in multiple tissues leads to premature cataracts and tendon xanthomas in late childhood, followed by progressive neurological dysfunction such as ataxia, dementia, and polyneuropathy.