Cerebrotendinous xanthomatosis (CTX) is an inherited lipid storage disorder that causes progressive neurological problems. This is due to the defective enzyme sterol 27-hydroxylase. Infants with CTX may have chronic diarrhea. They will also develop cataracts. Teenagers and young adults with CTX develop nodules on the Achilles tendon and on tendons of the hands, elbows, knees, and neck. These nodules may also occur in the lungs, bones, and brain. The majority of individuals with CTX are intellectually normal until puberty. In adulthood, individuals with CTX develop neurological problems which may include intellectual disability or dementia, seizures, hallucinations, depression, and difficulty coordinating movement and speech. Long-term treatment with chenodeoxycholic acid (CDCA) has shown to stabilize many of the symptoms associated with CTX except for neurologic deficits. CTX is caused by pathogenic variants in the CYP27A1 gene.