This information is provided by the National Institutes of Health (NIH) Genetic and Rare Diseases Information Center (GARD).
Hereditary geniospasm is a movement disorder that causes episodes of involuntary tremors of the chin and lower lip. The episodes may last anywhere from a few seconds to hours and may occur spontaneously or be brought on by stress. The episodes usually first appear in infancy or childhood and tend to lessen in frequency with age. Hereditary geniospasm is believed to be inherited in an autosomal dominant pattern. Although the exact gene that causes the condition is unknown, it has been suggested that mutations in a gene on chromosome 9 may be responsible in some families.
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