Hereditary Geniospasm

Hereditary geniospasm is a movement disorder characterized by episodes of involuntary tremor of the chin and lower lip.

Epidemiology

The disorder has been described in less than 25 families from Europe and the USA, with a slight male preponderance (male-to-female ratio of 1.3:1).

Clinical description

Onset usually occurs in childhood and may be precipitated by stress and emotion. Episodes may occur during sleep. There are no associated neurological abnormalities, although abnormal EEG, sleep disorders and involvement of other facial muscles have occasionally been described. Spontaneous improvement with age is possible.

Etiology

A locus has been identified at 9q13-q21 in a single four-generation British family. However, no linkage to this region was found in a second British family with the disease, indicating genetic heterogeneity.

Genetic counseling

Inheritance is autosomal dominant.