Peripheral nerve hyperexcitability syndrome comprises a heterogeneous group of diseases, clinically characterised by myokymia, fasciculation, muscle cramps and stiffness. The causes are either immune mediated or non-immune mediated. Non-immune-mediated forms are mostly genetic, relating to two main genes: KCNQ2 and KCNA1. Patients with KCNQ2 gene mutations typically present with epileptic encephalopathy, benign familial neonatal seizures and myokymia, though occasionally with purely peripheral nerve hyperexcitability. We report a woman with marked facial myokymia and distal upper limb contractures whose mother also had subtle facial myokymia; both had the c.G620A (p.R207Q) variant in the KCNQ2 gene. Patients with familial myokymia and peripheral nerve hyperexcitability syndrome should be investigated for KCNQ2 variants. This autosomal dominant condition may respond to antiepileptic medications acting at potassium channels.
- peripheral nerve hyperexcitability syndrome
- KCNQ2 gene mutations
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Contributors CGC: Study concept, acquisition and analysis of data, literature review and initial draft of the paper. AMSS: Study concept, acquisition and analysis of data, literature review, and initial draft of the paper. CAMM: Acquisition and analysis of data, literature review, and genetics analysis. CM-J: Acquisition and analysis of data, literature review. COH: Acquisition and analysis of data, literature review, electroneuromyography anaylisis. JLP: Study concept, acquisition and analysis of data, literature review, and critical revision of manuscript for intellectual content. EZ: Study concept, acquisition and analysis of data, literature review and critical revision of manuscript for intellectual content.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Obtained.
Provenance and peer review Not commissioned; externally peer reviewed by Jennifer Spillane, London, UK.
Data availability statement All data relevant to the study are included in the article or uploaded as supplementary information.