PRKCG mutation (SCA-14) causing a Ramsay Hunt phenotype

Area of Science:

• Genetics
• Neurology
• Molecular Biology

Background:

• Progressive myoclonic ataxia (PMA), or Ramsay Hunt syndrome, involves myoclonus, cerebellar ataxia, and sometimes seizures.
• Differential diagnosis of PMA includes progressive myoclonic epilepsy, but identifying specific causes in PMA is challenging.
• Spinocerebellar ataxias (SCAs) are a group of inherited neurodegenerative disorders affecting balance and coordination.

Observation:

• A patient presented with multifocal myoclonus in his thirties, later developing cerebellar ataxia and focal dystonia.
• The patient's father exhibited a similar clinical presentation.
• Genetic analysis identified a mutation in the protein kinase C gamma (PRKCG) gene.

Findings:

• The identified PRKCG gene mutation is known to cause spinocerebellar ataxia type 14 (SCA-14).
• This case demonstrates that myoclonus and dystonia are part of the clinical spectrum of SCA-14.
• Myoclonus can be the initial presenting symptom in SCA-14.

Implications:

• SCA-14 should be considered in the differential diagnosis of progressive myoclonic ataxia.
• Understanding the expanded clinical phenotype of SCA-14 aids in diagnosing patients with unexplained myoclonic and ataxic syndromes.
• Genetic testing for PRKCG mutations can improve diagnostic yield in patients with features of PMA.