Hereditary geniospasm

Alternate names

Trembling chin; GSM 1; Hereditary chin tremor/myoclonus; Geniospasm

Definition

Hereditary geniospasm is a movement disorder that causes episodes of involuntary tremors of the chin and lower lip.

Cause

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.

Inheritance

Autosomal dominant pattern, a 50/50 chance.

• Hereditary geniospasm is inherited in an autosomal dominant manner.
• This means that having only one mutated copy of the causative gene in each body cell is sufficient to cause signs and symptoms of the condition.
• When an individual with an autosomal dominant condition has children, each child has a 50% (1 in 2) chance to inherit the mutated copy of the gene and also be affected.
• Because there is a 50% chance for each child, it is possible for all of the children of an affected individual to be affected, or likewise, for all of the children to be unaffected.

Signs and symptoms

• It 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.

Diagnosis

The condition can be diagnosed on the basis of a clinical evaluation performed by a health care professional such as a neurologist who specializes in movement disorders.

Treatment

• Hereditary geniospasm, which may also be referred to as hereditary essential chin myoclonus, is generally considered a benign disorder although in some cases it can cause anxiety and social embarrassment.
• Significant improvement with age has been reported.
• Several drugs are used to treat myoclonus, such as benzodiazepines and anticonvulsants.
• However, individuals may not respond to a single medication and may experience significant side effects if a combination of drugs is used.
• It has also been suggested that botulinum toxin be considered as a primary treatment because it has been shown to be effective and well tolerated.

NIH genetic and rare disease info

• NIH info on Hereditary geniospasm

Hereditary geniospasm is a rare disease.

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