CTX? Never Heard of It

How a genetic mutation can lead to pediatric cataract, diarrhea, and psychotic disorders—and how optometrists can identify it early.

By Mel Friedman, OD

Cerebrotendinous xanthomatosis (CTX) is a rare autosomal recessive lipid storage disease with multiorgan involvement.1 Optometrists can play a major role in identifying patients with CTX, as many patients first manifest the condition in childhood with ocular symptoms. A pediatric patient presenting with early onset bilateral cataracts should raise a red flag as a potential CTX patient, and the optometrist should consider CTX in the differential diagnosis until evidence to the contrary is established.

IDENTIFYING CTX

Optometrists who suspect that a patient may have CTX should ask simple but direct questions to the patient and his or her parents; the answers should be used to determine whether a workup for CTX is appropriate. These questions should include whether the patient has recently experienced gastrointestinal disturbance or diarrhea, spastic movements, or other neurologic dysfunction.2,3

Symptoms may present as early at 2 years in some patients, and early detection of CTX may increase the chances of a favorable outcome following treatment.4 Symptoms are numerous and are outlined in the infographic Clinical Signs and Symptoms of CTX below.

A PRIMER ON CTX

CTX is the result of a mutation in the gene CYP27A1, which encodes for a cytochrome known as sterol 27-hydroxylase. The proteins resulting from normal-functioning sterol 27-hydroxylase help break down cholesterol to form the bile acids necessary for the body to digest fats. Mutations in sterol 27-hydroxylase damage the body’s capacity to break down cholesterol into a bile acid. As a result of this mutation, plasma cholesterol remains at normal levels while a significant increase in bile alcohol levels and steroid cholestanol levels are present. Excess bile alcohols are excreted via bile, urine, and feces, and cholestanol accumulates in the brain, peripheral nerves, and tendons—as well as in the lenses, resulting in cataract development.5

CTX is rare, but “genetic islands of high frequency have been reported.”1 Some developed nations, such as Denmark, have only recently documented cases of CTX,5 and researchers have estimated that nearly 1 in 72,000 North American patients could have CTX.6

MORE TO COME

In a future article on this topic in AOC, I will discuss specific tests used to detect CTX, the mechanism underlying the progressive nature of this disease, treatments for CTX, and the prognosis for this deadly disease.

The author thanks Paul Karpecki, OD, for advising and educating the author on the process, treatment, and implications of CTX.

1. Appadurai V, DeBarber A, Chiang PW, et al. Apparent underdiagnosis of cerebrotendinous xanthomatosis revealed by analysis of ~60,000 human exomes. Mol Genet Metab. 2015;111(4):298-304.

2. Chen C, Zhang Y, Wu H, et al. Clinical and molecular genetic features of cerebrotendinous xanthomatosis parents of Chinese families [published online ahead of print June 17, 2017]. Metab Brain Dis.

3. Abdel-Hamid MS, Issa MY Otaify GA, Zaki MS. A novel frameshift mutation in the sterol 27-hydroxylase gene in an Egyptian family with cerebrotendinous xanthomatosis without cataract. Metab Brain Dis. 2017;32(2):311-315.

4. Larson A, Weisfeld-Adams JD, Benke TA, Bonnen PE. Cerebrotendinous xanthomatosis presenting with infantile spams and intellectual disability [published online ahead of print November 18, 2016]. JIMD Rep.

5. Fraidakis MJ. Psychiatric manifestations in cerebrotendinous xanthomatosis. Transl Psychiatry. 2013;3:e302.

6. Keren Z, Falik-Zaccai TC. Cerebrotendinous xanthomatosis (CTX): a treatable lipid storage disease. Pediatr Endocrinol Rev. 2009;7(1):6-11.

1. Keren Z, Falik-Zaccai TC. Cerebrotendinous xanthomatosis (CTX): a treatable lipid storage disease. Pediatr Endocrinol Rev. 2009;7(1):6-11.

2. Moghadasian MH, Salen G, Frohlich JJ, Scudamore CH. Cerebrotendinous xanthomatosis: a rare disease with diverse manifestations. Arch Neurol. 2002;59(4):527-529.

3. Rosafio F, Cavallieri F, Guaraldi P, et al. The wide spectrum of cerebrotendinous xanthomatosis: case report of a rare but treatable disease. Clin Neurol Neurosurg. 2016;143:1-3.

4. Blaabjerg M, Marjanovic D. Cerebrotendinous xanthomatosis is a rare disorder, which requires a specific treatment [article in Danish]. Ugeskr Laeger. 2013;175(5):285-286.

5. Cerqueira AC, Nardi AE, Bezerra JM. Cerebrotendinous xanthomatosis: a treatable hereditary neuro-metabolic disease. Clinics (Sao Paulo). 2010;65(11):1217-1218.

6. Appadurai V, DeBarber A, Chiang PW, et al. Apparent underdiagnosis of cerebrotendinous xanthomatosis revealed by analysis of ~60,000 human exomes. Mol Genet Metab. 2015;111(4):298-304.

Mel Friedman, OD, FAAO
• optometrist, For Your Eyes Only, Memphis, Tenn.; adjunct professor, University of Alabama at Birmingham, Birmingham, Ala.

• financial disclosure: none relevant

dfried007@aol.com