4-month old presented with a trembling chin and mild upper respiratory tract infection, diagnosed with hereditary geniospasm
A 4-month-old boy with a trembling chin was taken to the paediatric clinic for examination of a mild upper respiratory infection. Involuntary myoclonus of the chin and lower lip was detected during evaluation (see video). Otherwise, the neurologic evaluation was normal. The patient’s parents said he had chin trembling since birth. The patient’s father, paternal aunt, paternal grandmother, paternal great-aunt, and paternal great-grandmother all had comparable chin myoclonus from infancy to maturity. Based on the findings, the patient was diagnosed with hereditary geniospasm.
Hereditary geniospasm, also known as hereditary chin tremor, is a genetic movement condition that can be sporadic or autosomal dominant, as in this case. It causes isolated myoclonus of the mentalis muscle. It is a rare, harmless disorder that may improve with age. Botulinum toxin injections may be a helpful treatment in people with more severe symptoms such as tongue biting or psychological anguish. The patient’s parents were encouraged to exercise caution while waiting. There was no genetic testing.
Is there a linkage to chromosome 9q13-q21?
Hereditary geniospasm is a movement disease that causes involuntary tremors of the chin and lower lip. Episodes often begin in childhood and can be triggered by stress, focus, or emotion. Hereditary geniospasm is an autosomal dominant trait that has no recognised aetiology. The findings of a genomewide genetic linkage research in a four-generation British family with hereditary geniospasm are presented. Positive two-point LOD scores were obtained for 15 microsatellite markers on chromosome 9’s peri-centromeric region. The marker D9S1837 received a maximum two-point LOD score of 5.24 at =.00.
The marker D9S1837 received a maximum two-point LOD score of 5.24 at =.00. The haplotype construction defined a 2.1 cM interval between the flanking markers D9S1806 and D9S175, allocating one locus for hereditary geniospasm to the proximal long arm of chromosome 9q13-q21. A second British family with hereditary geniospasm is not linked to this location, demonstrating genetic variability. These findings could have ramifications for other undiagnosed hereditary focused movement disorders.
When do the symptoms first appear?
The age at which symptoms may appear varies between diseases. Symptoms might appear at any age, or they can appear at many different age ranges. Some disorders can cause symptoms at any age. Knowing when symptoms first appeared can assist medical practitioners in making the accurate diagnosis.
Hereditary geniospasm is a movement disorder characterised by involuntary chin and lower lip spasms. The episodes can last from a few seconds to many hours and can occur spontaneously or as a result of stress. The episodes typically begin in infancy or youth and decrease in frequency with adulthood. Hereditary geniospasm is thought to be passed down in an autosomal dominant fashion.
Conclusion
Hereditary geniospasm is a movement disease characterised by involuntary chin and lower lip spasms. The episodes can last from a few seconds to many hours and can occur spontaneously or as a result of stress. The episodes typically begin in infancy or youth and decrease in frequency with adulthood. Hereditary geniospasm is thought to be passed down in an autosomal dominant fashion. Although the particular gene that causes the illness is unknown, mutations in a gene on chromosome 9 have been linked to the condition in some families.
Source: NEJM
