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KembaraXtra-Medicine – Ataxia Telangiectasia (AT)
Ataxia telangiectasia (AT) is a rare autosomal recessive childhood disorder caused by defective DNA repair. It is a multisystem condition characterized by progressive cerebellar ataxia, abnormal movements (e.g., choreoathetosis), oculocutaneous telangiectasias, recurrent infections from immune dysfunction, marked sensitivity to ionizing radiation, and an increased risk of malignancy. The ICD-10CM code is G11.3 (cerebellar ataxia with defective DNA repair).
AT occurs in about 1 in 40,000 live births, affects males and females equally, and typically begins in early childhood (often ages 1–5 years). It is considered the second most common autosomal recessive ataxia after Friedreich ataxia. The causative gene is ATM (mapped to chromosome 11q22–23), and many different mutations have been identified. The ATM protein is a kinase activated by double-stranded DNA breaks, triggering pathways for cell cycle arrest, DNA repair, or apoptosis. ATM is also important for V(D)J recombination in developing lymphocytes, which helps explain the immune problems seen in AT.
Children often develop normally until they begin walking, when gait and truncal ataxia become noticeable. Over time, symptoms can include slurred speech, progressive difficulty coordinating eye movements (including oculomotor apraxia), polyneuropathy, choreoathetosis, delayed physical and sexual development, and features of premature aging (such as early graying and skin/subcutaneous fat changes). Motor skills gradually decline, and by the second decade, many individuals require a wheelchair for at least part of the day. As the condition progresses, oromotor and swallowing difficulties can increase the risk of aspiration. Cognitive function is often initially normal and may decline early, then tends to plateau around about 10 years of age, though motor impairment can make school performance and timed testing look worse than true cognitive ability.
Telangiectasias are highly suggestive of AT but often appear later—typically after age 6—which can delay diagnosis. They commonly involve the bulbar conjunctiva (sometimes mistaken for conjunctivitis) and can also appear on the ears, cheeks, corners of the eyes, neck, nasal bridge, and flexor forearm creases. Skin findings may include café-au-lait macules, hypopigmented macules, or melanocytic nevi. Immune dysfunction affects 60%–80% of patients and stems from B-cell and T-helper problems. IgA is absent in many patients, IgE is low/absent in most, and IgM may be elevated; this predisposes to recurrent sinopulmonary infections. While the immune deficiency itself is typically not progressive, repeated infections and aspiration can contribute to bronchiectasis later in life.
Neuropathology includes progressive cerebellar injury with loss of Purkinje cells, and later changes may involve posterior columns and spinocerebellar tracts, with reports of anterior horn cell involvement and peripheral nerve changes. Cancer risk becomes increasingly important with age: beyond about 10 years, the incidence has been described as roughly 1% per year, with an overall lifetime risk around 30%–40%, most commonly leukemia and lymphoma. Carriers (heterozygotes) usually do not have classic AT symptoms but may have a higher malignancy risk at younger ages.
Diagnosis is based on the clinical picture (early-onset progressive ataxia plus telangiectasia and/or immune abnormalities), family history, and supportive testing. The differential for early-onset ataxia includes Friedreich ataxia, abetalipoproteinemia, acquired vitamin E deficiency, AOA1/AOA2, AT-like disorder, various spinocerebellar ataxias, certain metabolic diseases (e.g., Hartnup disease, maple syrup urine disease), and leukodystrophies. Helpful laboratory findings can include abnormal immunoglobulin levels, and serum α-fetoprotein, which is elevated in more than 95% of children with AT older than about 8 months. Some patients have acanthocytes on smear. Immunoblot testing for ATM protein is highly sensitive/specific, and many affected individuals have little to no detectable ATM protein. Brain MRI or CT typically shows cerebellar atrophy during childhood; imaging may also show findings compatible with telangiectasia-related changes.
There is no proven disease-specific cure, so management focuses on monitoring and reducing complications. This includes close surveillance for infections and cancers, consideration of IV immunoglobulin for those with frequent/severe infections, and sometimes prophylactic antibiotics. Routine preventive care is important, including influenza and pneumococcal vaccination. Because of radiation sensitivity, exposure to ionizing radiation should be minimized, including limiting diagnostic radiographs when possible. Swallowing should be monitored as needed to reduce aspiration risk, and physical/occupational therapy supports mobility and helps prevent contractures. Some studies suggest possible symptomatic improvement with glucocorticoids, thought to influence ATM splicing and preserve some kinase activity, but this is not established as definitive therapy. Antioxidants such as vitamin E are sometimes used empirically, though strong evidence is limited.
Prognosis is serious due to multisystem involvement, but survival has improved; many individuals now live beyond 25 years, and some into their 40s or 50s. Morbidity and mortality are most often related to recurrent infections or malignancy. Ongoing care typically involves coordinated referral to immunology, neurology, gastroenterology/nutrition, rehabilitation services, and genetic counseling.
Ataxia telangiectasia (AT) is a rare autosomal recessive childhood disorder caused by defective DNA repair. It is a multisystem condition characterized by progressive cerebellar ataxia, abnormal movements (e.g., choreoathetosis), oculocutaneous telangiectasias, recurrent infections from immune dysfunction, marked sensitivity to ionizing radiation, and an increased risk of malignancy. The ICD-10CM code is G11.3 (cerebellar ataxia with defective DNA repair).
AT occurs in about 1 in 40,000 live births, affects males and females equally, and typically begins in early childhood (often ages 1–5 years). It is considered the second most common autosomal recessive ataxia after Friedreich ataxia. The causative gene is ATM (mapped to chromosome 11q22–23), and many different mutations have been identified. The ATM protein is a kinase activated by double-stranded DNA breaks, triggering pathways for cell cycle arrest, DNA repair, or apoptosis. ATM is also important for V(D)J recombination in developing lymphocytes, which helps explain the immune problems seen in AT.
Children often develop normally until they begin walking, when gait and truncal ataxia become noticeable. Over time, symptoms can include slurred speech, progressive difficulty coordinating eye movements (including oculomotor apraxia), polyneuropathy, choreoathetosis, delayed physical and sexual development, and features of premature aging (such as early graying and skin/subcutaneous fat changes). Motor skills gradually decline, and by the second decade, many individuals require a wheelchair for at least part of the day. As the condition progresses, oromotor and swallowing difficulties can increase the risk of aspiration. Cognitive function is often initially normal and may decline early, then tends to plateau around about 10 years of age, though motor impairment can make school performance and timed testing look worse than true cognitive ability.
Telangiectasias are highly suggestive of AT but often appear later—typically after age 6—which can delay diagnosis. They commonly involve the bulbar conjunctiva (sometimes mistaken for conjunctivitis) and can also appear on the ears, cheeks, corners of the eyes, neck, nasal bridge, and flexor forearm creases. Skin findings may include café-au-lait macules, hypopigmented macules, or melanocytic nevi. Immune dysfunction affects 60%–80% of patients and stems from B-cell and T-helper problems. IgA is absent in many patients, IgE is low/absent in most, and IgM may be elevated; this predisposes to recurrent sinopulmonary infections. While the immune deficiency itself is typically not progressive, repeated infections and aspiration can contribute to bronchiectasis later in life.
Neuropathology includes progressive cerebellar injury with loss of Purkinje cells, and later changes may involve posterior columns and spinocerebellar tracts, with reports of anterior horn cell involvement and peripheral nerve changes. Cancer risk becomes increasingly important with age: beyond about 10 years, the incidence has been described as roughly 1% per year, with an overall lifetime risk around 30%–40%, most commonly leukemia and lymphoma. Carriers (heterozygotes) usually do not have classic AT symptoms but may have a higher malignancy risk at younger ages.
Diagnosis is based on the clinical picture (early-onset progressive ataxia plus telangiectasia and/or immune abnormalities), family history, and supportive testing. The differential for early-onset ataxia includes Friedreich ataxia, abetalipoproteinemia, acquired vitamin E deficiency, AOA1/AOA2, AT-like disorder, various spinocerebellar ataxias, certain metabolic diseases (e.g., Hartnup disease, maple syrup urine disease), and leukodystrophies. Helpful laboratory findings can include abnormal immunoglobulin levels, and serum α-fetoprotein, which is elevated in more than 95% of children with AT older than about 8 months. Some patients have acanthocytes on smear. Immunoblot testing for ATM protein is highly sensitive/specific, and many affected individuals have little to no detectable ATM protein. Brain MRI or CT typically shows cerebellar atrophy during childhood; imaging may also show findings compatible with telangiectasia-related changes.
There is no proven disease-specific cure, so management focuses on monitoring and reducing complications. This includes close surveillance for infections and cancers, consideration of IV immunoglobulin for those with frequent/severe infections, and sometimes prophylactic antibiotics. Routine preventive care is important, including influenza and pneumococcal vaccination. Because of radiation sensitivity, exposure to ionizing radiation should be minimized, including limiting diagnostic radiographs when possible. Swallowing should be monitored as needed to reduce aspiration risk, and physical/occupational therapy supports mobility and helps prevent contractures. Some studies suggest possible symptomatic improvement with glucocorticoids, thought to influence ATM splicing and preserve some kinase activity, but this is not established as definitive therapy. Antioxidants such as vitamin E are sometimes used empirically, though strong evidence is limited.
Prognosis is serious due to multisystem involvement, but survival has improved; many individuals now live beyond 25 years, and some into their 40s or 50s. Morbidity and mortality are most often related to recurrent infections or malignancy. Ongoing care typically involves coordinated referral to immunology, neurology, gastroenterology/nutrition, rehabilitation services, and genetic counseling.
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