David T Hsieh MD (

Dr. Hsieh of the Uniformed Services University of the Health Sciences has no relevant financial relationships to disclose.

Michael V Johnston MD, editor. (

Dr. Johnston of Johns Hopkins University School of Medicine has no relevant financial relationships to disclose.

Originally released July 12, 1994; last updated June 12, 2020; expires June 12, 2023

This article includes discussion of ataxia-telangiectasia and Louis-Bar syndrome. The foregoing terms may include synonyms, similar disorders, variations in usage, and abbreviations.


Ataxia-telangiectasia is an autosomal recessive condition of genomic instability that clinically presents in childhood as progressive ataxia and incoordination, dilated blood vessels of skin and conjunctiva, frequent sinus and pulmonary infections due to immune deficiencies, and an increased risk of certain malignancies. Elevated serum alpha-fetoprotein is seen in over 90% of patients; molecular testing of the ataxia telangiectasia mutated (ATM) gene is clinically available. In this article, the author provides updates on the treatment of dystonia and the phenotype in long-term survivors of ataxia-telangiectasia.

Key points


• Ataxia-telangiectasia is an autosomal recessive condition characterized by progressive childhood ataxia, oculomotor apraxia, some degree of immunodeficiency, an increased risk for certain malignancies, and telangiectasias of the skin and conjunctiva.


• Elevated serum alpha-fetoprotein is an important biochemical marker because the hallmark telangiectasias do not appear until later in the clinical course.


• The principle defect is in the ataxia-telangiectasia mutated (ATM) gene, whose end product is a protein kinase involved in cell cycle regulation.


• Patients are at an increased risk for certain malignancies, primarily leukemias and lymphomas, and are hypersensitive to ionizing radiation.


• Patients with variant ataxia-telangiectasia may present initially with extrapyramidal movement disorders but are also at an increased risk for malignancy and hypersensitivity to ionizing radiation.

Historical note and terminology

In 1926, Syllaba and Henner first described the association of oculocutaneous telangiectasias with choreoathetosis. Louis-Bar reported the combination of oculocutaneous telangiectasias with progressive cerebellar ataxia in 1941. In 1958, Boder and Sedgwick studied 8 cases from 5 unrelated families, including 6 familial cases. They emphasized the heredofamilial nature of the disease and the susceptibility of these patients to sinopulmonary infections. They named this syndrome ataxia-telangiectasia (Boder and Sedgwick 1958). Ataxia-telangiectasia is now recognized as 1 of a group of recessive hereditary genomic instability disorders and is characterized by progressive neurodegeneration, immunodeficiency, and cancer susceptibility.

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