The animated videos in NORD’s Rare Disease Video Library provide brief introductions to rare disease topics for patients, caregivers, students, professionals and the public. NORD collaborates with medical experts, patient organizations, videographers and Osmosis to develop the videos, which are made possible by individual donations, educational grants and corporate sponsorships. NORD is solely responsible for the content.
Summary
Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive genetic disorder caused by an abnormality in the CYP27A1 gene, resulting in a deficiency of the mitochondrial enzyme sterol 27-hydroxylase. The lack of this enzyme prevents cholesterol from being converted into a bile acid called chenodeoxycholic acid. Deposits of cholesterol and a related compound called cholestanol accumulate in the nerve cells and membranes potentially causing damage to the brain, spinal cord, tendons, lens of the eye and arteries. Affected individuals can experience diarrhea and cataracts in childhood and may develop benign, fatty tumors (xanthomas) of the tendons during adolescence. If untreated, CTX can lead to progressive neurologic problems such as seizures, cognitive impairment, and difficulties with coordination and balance (ataxia). Coronary heart disease is common. Some individuals with the later-onset symptoms of CTX experienced cholestatic jaundice during infancy. The specific symptoms and progression of this disorder can vary greatly from one individual to another, even for twins with the same abnormality in the CYP27A1 gene. Long-term therapy with chenodeoxycholic acid has been effective in treating affected individuals.
Introduction
CTX was first described in the medical literature in 1937. CTX is classified as a bile acid synthesis disorder (due to the underlying genetic mutation that causes deficiency in an important enzyme in the bile acid synthesis pathway; sterol 27-hydroxylase). Bile acids (chenodeoxycholic and cholic acid) are mostly synthesized in the liver. They are an important component of bile and help the intestine to absorb fats. The disorder can also be classified as a lipid storage disorder (due to fat deposition in various tissues of the body) or a leukodystrophy (due to the involvement of central nervous system white matter).
