Cerebrotendinous xanthomatosis presenting with severe externalized disorder: improvement after one year of treatment with chenodeoxycholic Acid.

Cerebrotendinous xanthomatosis (CTX) is a rare inborn disorder of sterol storage with autosomal recessive inheritance and a variable clinical presentation. We describe two siblings with an early psychiatric presentation of CTX-associated attention-deficit/hyperactivity disorder and oppositional defiant disorder, also associated with a mild intellectual disability and major behavioral impairments. In both cases, treatment with chenodeoxycholic acid improved externalized symptoms and a partial recovery of cognitive impairments was observed. This suggests that CTX is potentially reversible, demonstrating the need for early diagnosis and treatment of this disorder before irreversible neurological lesions can occur.