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Ataxia telangiectasia (A-T) (also referred to as Louis–Bar syndrome〔D. Louis-Bar. Sur un syndrome progressif cormprenant des télangiectasies capillaires cutanées et conjonctivales symétriques, à disposition naevoïde et des troubles cérébelleux. Confinia Neurologica 1941; 4: 32-42.〕 ) is a rare, neurodegenerative, inherited disease causing severe disability. Ataxia refers to poor coordination and telangiectasia to small dilated blood vessels, both of which are hallmarks of the disease. A-T affects many parts of the body: * It impairs certain areas of the brain including the cerebellum, causing difficulty with movement and coordination. * It weakens the immune system, causing a predisposition to infection. * It prevents repair of broken DNA, increasing the risk of cancer. Symptoms most often first appear in early childhood (the toddler stage) when children begin to walk. Though they usually start walking at a normal age, they wobble or sway when walking, standing still or sitting, and may appear almost as if they are drunk. In late pre-school and early school age, they develop difficulty moving their eyes in a natural manner from one place to the next (oculomotor apraxia). They develop slurred or distorted speech, and swallowing problems. Some have an increased number of respiratory tract infections (ear infections, sinusitis, bronchitis, and pneumonia). Because not all children develop in the same manner or at the same rate, it may be some years before A-T is properly diagnosed. Most children with A-T have stable neurologic symptoms for the first 4–5 years of life, but begin to show increasing problems in early school years. A-T is caused by a defect in the ATM gene, which is responsible for managing the cell’s response to multiple forms of stress including double-strand breaks in DNA. In simple terms, the protein produced by the ATM gene recognizes that there is a break in DNA, recruits other proteins to fix the break, and stops the cell from making new DNA until the repair is complete. == Symptoms == There is substantial variability in the severity of features of A-T among affected individuals, and at different ages. The following symptoms or problems are either common or important features of A-T: * Ataxia (difficulty with control of movement) that is apparent early but worsens in school to pre-teen years * Oculomotor apraxia (difficulty with coordination of head and eye movement when shifting gaze from one place to the next) * Involuntary movements * Telangiectasia (dilated blood vessels) over the white (sclera) of the eyes, making them appear bloodshot. These are not apparent in infancy and may first appear at age 5–8 years. Telangiectasia may also appear on sun-exposed areas of skin. * Problems with infections, especially of the ears, sinuses and lungs * Increased incidence of cancer (primarily, but not exclusively, lymphomas and leukemias) * Delayed onset or incomplete pubertal development, and very early menopause * Slowed rate of growth (weight and/or height) * Drooling particularly in young children when they are tired or concentrating on activities * Dysarthria (slurred, slow, or distorted speech sounds) * Diabetes in adolescence or later * Premature changes in hair and skin Many children are initially misdiagnosed as having ataxic cerebral palsy. The diagnosis of A-T may not be made until the preschool years when the neurologic symptoms of impaired gait, hand coordination, speech and eye movement appear or worsen, and the telangiectasia first appear. Because A-T is so rare, doctors may not be familiar with the symptoms, or methods of making a diagnosis. The late appearance of telangiectasia may be a barrier to the diagnosis. It may take some time before doctors consider A-T as a possibility because of the early stability of symptoms and signs. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「ataxia telangiectasia」の詳細全文を読む スポンサード リンク
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