Two brothers with an IQSEC2 pathogenic variant presented with early onset intellectual disability, intractable epileptic seizures, autism spectrum disorders, postnatal microcephalus and slowly progressive rigid-spasticity. Their epileptic seizures were characterized by intractability, early onset epileptic spasms, and then clusters of tonic/tonic-clonic seizures, exacerbated by valproate. Electroencephalography showed periodic discharges, including periodic high voltage slow complexes and burst-suppression activity. Whole exome sequencing, using DNA from peripheral blood of both brothers, identified a pathogenic variant, c.2776 C > T, p.(Arg 926*) in exon 9 of IQSEC2 (NM 001111125.3). Their parents and another brother did not have this variant, which may suggest that maternal gonadal mosaicism is the most likely mechanism.

中文翻译：

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IQSEC2 致病性变异两兄弟的脑电图发现和遗传特征

具有 IQSEC2 致病性变异的两兄弟出现了早发性智力障碍、顽固性癫痫发作、自闭症谱系障碍、产后小头症和缓慢进行性强直性痉挛。他们的癫痫发作的特点是难治性、早发性癫痫痉挛，然后是强直/强直阵挛发作，丙戊酸加剧。脑电图显示周期性放电，包括周期性高压慢复合物和爆发抑制活动。使用来自两兄弟外周血的 DNA 进行全外显子组测序，在 IQSEC2 (NM 001111125.3) 的外显子 9 中鉴定出一个致病变异 c.2776 C > T, p.(Arg 926*)。他们的父母和另一个兄弟没有这种变异，这可能表明母体性腺嵌合体是最可能的机制。