Longitudinal study of EEG patterns in a child with a KCNH1 mutation showing non-epileptic myoclonus

Takeshi Inoue , Kei Ohashi , Ayako Hattori , Mariko Saito , Tomoshige Tanimura , Daisuke Ieda , Kyoko Ban , Fuyuki Miya , Shinji Saitoh
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Abstract

Introduction

The potassium voltage-gated channel subfamily H member 1 is encoded by the KCNH1 gene. Mutations in KCNH1 result in Temple-Baraitser (TBS) and Zimmermann-Laband (ZLS) syndromes, which are characterized by developmental delay, epilepsy, and nail dysplasia. These syndromes have clinical overlap and are found in patients with atypical TBS/ZLS phenotypic features. Although KCNH1-related diseases are associated with a high incidence of epilepsy, electroencephalogram (EEG) changes over time have not been studied. In this study, we investigated the longitudinal evolution of EEG findings and types of seizures from the neonatal period to 6 years of age in a patient with a KCNH1 variant.

Case report

A 6-year-old girl showed features of KCNH1-related disease. Exome analysis revealed a heterozygous de novo missense variant (NM_172362.3; c.1481T>C; p.Ile494Thr) in KCNH1. She presented generalized tonic-clonic seizures (GTCS) at the age of 3 years and 1 month. She also presented with myoclonus in the neonatal period, determined to be involuntary movement because of the absence of corresponding EEG discharges and persistence. The EEG findings evolved as follows: normal at 1 month of age, multifocal spikes started at 3 months of age, and high-voltage slow waves started at 3 months of age, which initially appeared during awake periods.

Conclusion

Patients with a KCNH1 variant may have GTCS and involuntary movements including myoclonus. Furthermore, high-voltage slow waves in EEG, which are characteristic of patients with KCNH1 variants, were not observed immediately after birth but appeared at several months of age.
纵向研究脑电图模式与KCNH1突变的儿童显示非癫痫性肌阵挛
钾电压门控通道亚家族H成员1由KCNH1基因编码。KCNH1突变导致坦普尔-巴雷茨(TBS)和齐默曼-拉班(ZLS)综合征,其特征是发育迟缓、癫痫和指甲发育不良。这些综合征具有临床重叠,见于具有非典型TBS/ZLS表型特征的患者。虽然kcnh1相关疾病与癫痫的高发病率相关,但脑电图(EEG)随时间的变化尚未得到研究。在这项研究中,我们调查了一名KCNH1变异患者从新生儿期到6岁的脑电图结果和癫痫发作类型的纵向演变。病例报告:1例6岁女童表现出kcnh1相关疾病的特征。外显子组分析显示一个杂合的新生错义变异(NM_172362.3;c.1481T> C;p.Ile494Thr)在KCNH1中的表达。她在3岁零1个月时出现全身性强直阵挛发作(GTCS)。她还在新生儿期出现肌阵挛,由于没有相应的脑电图放电和持续存在,确定为不自主运动。脑电图表现如下:1月龄时正常,3月龄时开始出现多焦点峰,3月龄时开始出现高压慢波,最初出现在清醒期。结论KCNH1变异患者可能有GTCS和肌阵挛等不自主运动。此外,作为KCNH1变异患者特征的脑电图高电压慢波在出生后并未立即观察到,而是在几个月大时出现。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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