Diagnosis and Testing
How do I get tested for cerebrotendinous xanthomatosis?
A doctor may suspect a diagnosis of cerebrotendinous xanthomatosis because of the symptoms a person has. An infant with chronic diarrhea that doesn't respond to treatment or cataracts in young children, or cholestatic liver disease in infants without an apparent cause. Unexplained neurological disease in adolescents or adults can also be a sign. Even if a diagnosis isn't suspected, these symptoms might lead to a patient being referred to a specialist. A referral to local genetics clinic or a genetic metabolic specialist may also be made. Unfortunately, the symptoms of this disorder are so varied that a delay in diagnosis of many years is common. The mean age of diagnosis is around 35-37 years of age.
A suspected diagnosis should lead to biochemical testing. This type of testing measures the levels of certain chemicals in blood and urine samples. This includes measuring cholestanol concentration in the blood plasma or bile alcohol levels in the urine or blood plasma. These chemicals are found in high concentrations in people with cerebrotendinous xanthomatosis. A diagnosis can be confirmed by molecular genetic testing. This type of testing looks for the gene changes that cause the disorder. Both biochemical and molecular genetic testing must be done at specialized laboratories that have experience with cerebrotendinous xanthomatosis and related disorders.
Physicians have created a suspicion index, which assigns weighted scores indicators of cerebrotendinous xanthomatosis such as family history characteristics and common systemic and neurological features of the disorder. The indicators are classified as very strong (score 100), strong (50) or moderate (25).
A genetics professional nearby can discuss information and testing for CTX. A medical geneticist can be found by asking your doctor for a referral or looking on the American College of Medical Geneticists website . Genetic counselors in the United States can be found on the National Society of Genetic Counselors website. Genetic counselors in Canada can be found at the Canadian Association of Genetic Counselors website.
Cerebrotendinous Xanthomatosis. National Organization for Rare Disorders website. http://rarediseases.org/rare-diseases/cerebrotendinous-xanthomatosis/. Updated 2014. Accessed April 10, 2016.
Federico A, Dotti MT, Gahl W. Cerebrotendinous Xanthomatosis. GeneReviews website. http://www.ncbi.nlm.nih.gov/books/NBK1409/ Updated August 1, 2013. Accessed April 10, 2016.
Mignarri A, Gallus GN, Dotti MT, Federico A. A suspicion index for early diagnosis and treatment of cerebrotendinous xanthomatosis. J Inherit Metab Dis. 2014 May;37(3):421-9.