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At a Glance

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Rare hereditary neurodegenerative disorder, also called spinocerebellar ataxia type III, which is characterized by weakness of arms and legs, spasticity, and a staggering lurching gait easily mistaken from drunkenness. Other clinical features include dysphagia, severe nystagmus, dystonia, and twitching of the tongue. Some patients have peculiar exophthalmos.

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Synonyms

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Spinocerebellar Ataxia Type III; Machado Disease; Joseph Disease; Portuguese-Azorean Disease; Azorean Neurologic Disease; Spinocerebellar Atrophy Type III; Spinopontine Atrophy; Nigro-Spino-Dental Degeneration.

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Classification

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The differences in the types of Machado-Joseph disease (MJD) relate to the age of onset and severity.

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Machado-Joseph Disease Type I (MJD-I): Characterized by age of onset between 10 and 30 years and presents a rapid evolution. Clinical features include a combination of dystonic and spastic muscle in the arms and legs, ataxia often associated with athetosis and dysarthria (as observed with drunkenness, slurred speech), ophthalmoplegia, and exophthalmia. Mental alertness and intellectual capacities are unaffected.

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Machado-Joseph Disease Type II (MJD-II): Characterized by a symptomatology similar to that observed in type I; however, the progression of the disease is slower. The age of onset is usually between 20 and 50 years. The distinctive characteristic of MJD-II is the presence of ataxia associated with increasing hypertonicity in the arms and legs, leading to significant difficulties in controlling movements.

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Machado-Joseph Disease Type III (MJD-III): Characterized by a late onset between ages 40 and 70 years, severe ataxia, and slow degeneration of the central nervous system, particularly the hindbrain, motor polyneuropathy, and lateral amyotrophy. Individuals affected with this condition may become paralyzed early in their teens or during early adulthood. Individuals affected with this condition present with loss of feeling, lack of sensitivity to pain, impaired ability to coordinate movement of the arms and legs, and diabetes. The progression of type III disease is slowest of the three types.

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Incidence

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Machado-Joseph disease is one type of autosomal dominant spinocerebellar ataxia. More than 100 families worldwide have been described. Many of them live in the eastern United States and in Japan and have ancestors from Portugal or the Azorean Islands. Estimated to be 0.1:100,000 persons in Japan.

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Genetic Inheritance

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Machado-Joseph disease reflects a CAG triplet expansion on chromosome 14q32.1. Studies of numerous kindreds suggest the heterogeneous phenotypic expression of MJD may be related to the number of CAG repeats. A phenomenon of anticipation is associated a higher number of repeats with earlier onset.

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Pathophysiology

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Histologically, degenerative changes with neuronal loss and astrocytosis are seen in various loci of the cerebellum, midbrain, brainstem, and medulla.

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Diagnosis

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Based on the clinical manifestations, family history, and genetic analysis.

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Clinical Aspects

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Except for type I in which teens can begin to ...

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