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Spinocerebellar Ataxia 42

Spinocerebellar Ataxia 42

Patient Information

Characteristics

Background and History

This is one of many hereditary neurological disorders that impacts mobility and other functions of daily life.

Clinical Correlations

Symptoms generally appear in midlife or later and consist primarily of gait problems.  It is slowly progressive but the ultimate disability level is mild to moderate in most individuals.  They may experience some swallowing difficulties and speech is slurred.  An unsteady gait (ataxia) is common.  Muscles in the limbs are tight (spastic) and reflexes are increased.  Mild cognitive impairment and depression are present in a minority of individuals.  Studies of the brain show some loss of cells in specific areas such as the cerebellum.

Genetics

Inheritance

This is an autosomal dominant condition in which a gene change (mutation) in one member of a specific pair is present.  It follows a vertical pattern of transmission because the gene change is passed from parent to child with a 50% probability.

Pedigree

Autosomal dominant

Autosomal dominant disorders require only one mutation for the disease to be expressed.  Since an affected parent has two chromosomes, only one of which has the mutant gene, parents can expect that half (50%) of their children will receive that one and inherit the disease.  It is common for individuals that inherit the mutation, however, to not have evidence of the disease (nonpenetrance).

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Sample pedigree of autosomal dominant inheritance

Autosomal dominant inheritance leads to a vertical pattern of transmission

Diagnosis and Prognosis

Diagnosis of this disorder is most likely made by a neurologist.  There does not seem to be any impact on longevity.  No treatment is known.

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