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Dentatorubral pallidoluysian atrophy
Dentatorubral pallidoluysian atrophy (DRPLA) is a rare subtype of type I autosomal dominant cerebellar ataxia (ADCA type I; see this term). It is characterized by involuntary movements, ataxia, epilepsy, mental disorders, cognitive decline and prominent anticipation.
Worldwide prevalence is unknown. However, the disease is found most commonly in Japan where the prevalence is estimated to be 1/208,000.
Age of onset ranges from 1 to 60 years (mean age = 28.8 years). Patients with earlier onset (below 20 years of age) tend to show myoclonus epilepsy and intellectual deficit. Patients with late onset (over 40 years of age) tend to present with cerebellar ataxia, choreoathetosis and dementia. Clinical features and the age of onset are significantly correlated with the size of CAG repeats. Head magnetic resonance imaging (MRI) shows atrophy of cerebellum, brainstem, cerebrum and high signal has been shown in periventricular white matter.
Unstable expansion of CAG repeats in the ATN1 gene (12p13.31) has been demonstrated.
Prognosis is poor. DRPLA progresses rather rapidly. The mean disease duration is about 13 years. Recurrent seizures and dysphagia with frequent fluid and food aspiration lead to bronchopneumonia and subsequent death. However, some patients can reach 60 years of age or more.
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