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Ataxia–telangiectasia
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Ataxia–telangiectasia
Ataxia–telangiectasia (AT or A–T), also referred to as ataxia–telangiectasia syndrome or Louis–Bar syndrome, is a rare, neurodegenerative 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:
Symptoms most often first appear in early childhood (the toddler stage) when children begin to sit or walk. Though they usually start walking at a normal age, they wobble or sway when walking, standing still, or sitting. In late preschool and early school age, they develop difficulty naturally moving their eyes 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). Since children develop differently, 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 has an autosomal recessive pattern of inheritance.
A–T is caused by a defect in the ATM gene, named after this disease, which is involved in the recognition and repair of damaged DNA. Heterozygotes will not experience the characteristic symptoms, but it has been reported that they have higher risks of cancer and heart disease. The prevalence of A–T is estimated to be as high as 1 in 40,000 to as low as 1 in 300,000 people.
There is substantial variability in the severity of the signs and symptoms of A–T among affected individuals, and they may appear at different ages. The following symptoms or problems are either common or important features of A–T:[citation needed]
Many children are initially misdiagnosed as having 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 develops. 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 also take some time before doctors consider A–T as a possibility because of the early stability of symptoms and signs. Some patients have been diagnosed with A-T only in adulthood due to an attenuated form of the disease, and this has been correlated with the type of their gene mutation.
The first indications of A–T usually occur during the toddler years. Children start walking at a normal age, but may not improve much from their initial wobbly gait. Sometimes they have problems standing or sitting still and tend to sway backward or from side to side. During the primary school years, walking becomes more difficult, and children will use doorways and walls for support. Children with A–T often appear better when running or walking quickly in comparison to when they walk slowly or stand still. Around the beginning of their second decade, children with the more severe ("classic") form of A–T start using a wheelchair for long distances. During school years, children may have increasing difficulty with reading because of impaired coordination of eye movement. At the same time, other problems with fine motor functions (writing, coloring, and using utensils to eat) and with speech (dysarthria) may arise. Most of these neurologic problems stop progressing after the age of about 12 – 15 years, though involuntary movements may start at any age and may worsen over time. These extra movements can take many forms, including small jerks of the hands and feet that look like fidgeting (chorea), slower twisting movements of the upper body (athetosis), adoption of stiff and twisted postures (dystonia), occasional uncontrolled jerks (myoclonic jerks), and various rhythmic and non-rhythmic movements with attempts at coordinated action (tremors).
Prominent blood vessels (telangiectasia) over the white (sclera) of the eyes usually occur by the age of 5–8 years, but sometimes appear later or not at all. The absence of telangiectasia does not exclude the diagnosis of A–T. Potentially a cosmetic problem, the ocular telangiectasia does not bleed or itch, though they are sometimes misdiagnosed as chronic conjunctivitis. It is their constant nature, not changing with time, weather, or emotion, that marks them as different from other visible blood vessels. Telangiectasia can also appear on sun-exposed areas of skin, especially the face and ears. They occur in the bladder as a late complication of chemotherapy with cyclophosphamide, have been seen deep inside the brain of older people with A–T, and occasionally arise in the liver and lungs.
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Ataxia–telangiectasia
Ataxia–telangiectasia (AT or A–T), also referred to as ataxia–telangiectasia syndrome or Louis–Bar syndrome, is a rare, neurodegenerative 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:
Symptoms most often first appear in early childhood (the toddler stage) when children begin to sit or walk. Though they usually start walking at a normal age, they wobble or sway when walking, standing still, or sitting. In late preschool and early school age, they develop difficulty naturally moving their eyes 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). Since children develop differently, 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 has an autosomal recessive pattern of inheritance.
A–T is caused by a defect in the ATM gene, named after this disease, which is involved in the recognition and repair of damaged DNA. Heterozygotes will not experience the characteristic symptoms, but it has been reported that they have higher risks of cancer and heart disease. The prevalence of A–T is estimated to be as high as 1 in 40,000 to as low as 1 in 300,000 people.
There is substantial variability in the severity of the signs and symptoms of A–T among affected individuals, and they may appear at different ages. The following symptoms or problems are either common or important features of A–T:[citation needed]
Many children are initially misdiagnosed as having 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 develops. 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 also take some time before doctors consider A–T as a possibility because of the early stability of symptoms and signs. Some patients have been diagnosed with A-T only in adulthood due to an attenuated form of the disease, and this has been correlated with the type of their gene mutation.
The first indications of A–T usually occur during the toddler years. Children start walking at a normal age, but may not improve much from their initial wobbly gait. Sometimes they have problems standing or sitting still and tend to sway backward or from side to side. During the primary school years, walking becomes more difficult, and children will use doorways and walls for support. Children with A–T often appear better when running or walking quickly in comparison to when they walk slowly or stand still. Around the beginning of their second decade, children with the more severe ("classic") form of A–T start using a wheelchair for long distances. During school years, children may have increasing difficulty with reading because of impaired coordination of eye movement. At the same time, other problems with fine motor functions (writing, coloring, and using utensils to eat) and with speech (dysarthria) may arise. Most of these neurologic problems stop progressing after the age of about 12 – 15 years, though involuntary movements may start at any age and may worsen over time. These extra movements can take many forms, including small jerks of the hands and feet that look like fidgeting (chorea), slower twisting movements of the upper body (athetosis), adoption of stiff and twisted postures (dystonia), occasional uncontrolled jerks (myoclonic jerks), and various rhythmic and non-rhythmic movements with attempts at coordinated action (tremors).
Prominent blood vessels (telangiectasia) over the white (sclera) of the eyes usually occur by the age of 5–8 years, but sometimes appear later or not at all. The absence of telangiectasia does not exclude the diagnosis of A–T. Potentially a cosmetic problem, the ocular telangiectasia does not bleed or itch, though they are sometimes misdiagnosed as chronic conjunctivitis. It is their constant nature, not changing with time, weather, or emotion, that marks them as different from other visible blood vessels. Telangiectasia can also appear on sun-exposed areas of skin, especially the face and ears. They occur in the bladder as a late complication of chemotherapy with cyclophosphamide, have been seen deep inside the brain of older people with A–T, and occasionally arise in the liver and lungs.