AIM MOGS mutations cause congenital disorders of glycosylation type IIb (CDG-IIb or GCS1-CDG). The specific manifestations caused by the mutations in this gene remain unknown. We aimed to describe the clinical features of CDG- IIb and the effectiveness of urinary oligosaccharide analysis in the diagnosis of CDG- IIb. METHODS Patient 1 was analyzed with whole-exome sequencing (WES) to identify the causative gene of intractable epilepsy and severe developmental delay. After detecting MOGS mutation in patient 1, we analyzed patients 2 and 3 who were siblings and had clinical features similar to those in patient 1. Urinary oligosaccharide analysis was performed to confirm CDG- IIb diagnosis in patient 1. The clinical features of these patients were analyzed and compared with those in eight published cases. RESULTS Our three patients presented with early infantile epileptic encephalopathy, generalized hypotonia, hepatic dysfunction and dysmorphic features. In two cases, compound heterozygous mutations in MOGS were identified by WES. Isolation and characterization of the urinary oligosaccharide was performed in one of these cases to confirm the diagnosis of CDG-IIb. Although the isoelectric focusing of transferrin (IEF-T) of serum in this patient was normal, urinary excretion of Hex4 corresponding to Glc3Man was observed by mass spectrometry. CONCLUSION This report provides clinical manifestations of CDG-IIb with MOGS mutation. CDG-IIb shows a normal IEF profile of serum transferrin and cannot be detected by structural analysis of the patient's glycoproteins. Characterization of urinary oligosaccharides should be considered to detect this disorder.

中文翻译：

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具有 MOGS 突变的 IIb 型糖基化先天性疾病导致早期婴儿癫痫性脑病、畸形特征和肝功能障碍

AIM MOGS 突变导致 IIb 型糖基化先天性疾病（CDG-IIb 或 GCS1-CDG）。该基因突变引起的具体表现仍然未知。我们旨在描述 CDG-IIb 的临床特征和尿寡糖分析在 CDG-IIb 诊断中的有效性。方法 采用全外显子组测序（WES）对患者 1 进行分析，以确定难治性癫痫和严重发育迟缓的致病基因。在患者 1 中检测到 MOGS 突变后，我们分析了患者 2 和 3，他们是兄弟姐妹，临床特征与患者 1 相似。进行尿寡糖分析以确认患者 1 的 CDG-IIb 诊断。这些患者的临床特征是分析并与已发表的八个案例进行了比较。结果 我们的三名患者表现为早期婴儿癫痫性脑病、全身性张力减退、肝功能障碍和畸形特征。在两个案例中，WES 鉴定了 MOGS 中的复合杂合突变。在这些病例之一中进行了尿寡糖的分离和表征，以确认 CDG-IIb 的诊断。尽管该患者血清转铁蛋白（IEF-T）等电聚焦正常，但通过质谱观察到与 Glc3Man 相对应的 Hex4 尿排泄。结论 本报告提供了 CDG-IIb 伴 MOGS 突变的临床表现。CDG-IIb 显示血清转铁蛋白的正常 IEF 谱，无法通过患者糖蛋白的结构分析检测到。