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.

中文翻译：

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遗传性周围神经过度兴奋综合征中的面部肌无力

外周神经过度兴奋综合征包括一组异质性疾病，临床特征为肌肌束、肌束震颤、肌肉痉挛和僵硬。原因是免疫介导的或非免疫介导的。非免疫介导的形式大多是遗传的，涉及两个主要基因：KCNQ2 和 KCNA1。具有 KCNQ2 基因突变的患者通常表现为癫痫性脑病、良性家族性新生儿癫痫发作和肌无力，但偶尔会出现纯粹的外周神经过度兴奋。我们报告了一名有明显面部肌肌无力和上肢远端挛缩的女性，她的母亲也有轻微的面部肌肌无力；两者都在 KCNQ2 基因中具有 c.G620A (p.R207Q) 变体。家族性肌无力和外周神经过度兴奋综合征患者应检查 KCNQ2 变异。