The lymphohematopoietic cells originating from feto-maternal trafficking during pregnancy may cause microchimerism and lead to materno-fetal graft versus host disease (GVHD) in severe combined immunodeficiency (SCID) patients. However, definitive diagnosis between GVHD and Omenn’s syndrome is often difficult based on clinical and immunological phenotypes particularly in the patients with hypomorphic mutations. A 3-year-old girl with a history of erythroderma and immunodeficiency was studied. The whole exome sequencing method was used to find the disease-causing variants, and T-A cloning and Quantitative Florescence Polymerase Chain Reaction (QF-PCR) methods were utilized to detect the presence of mosaicism or microchimerism. We identified a homozygous missense Janus Kinase 3 mutation (JAK3, c.2324G>A, p.R775H) as a new disease-causing variant in the patient, and the presence of microchimerism with maternal origin was proven as an underlying cause of her clinical presentation. The findings highlighted the importance of appropriate diagnostic approach in GVHD cases with hypomorphic JAK3 mutations. When analyzing the results of the next generation sequencing, the possibility of microchimerism should be considered based on the context of the disease.

中文翻译：

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JAK3缺陷患者的移植物抗宿主病和微嵌合体

源自妊娠期间胎儿母体贩运的淋巴造血细胞可能导致严重联合免疫缺陷（SCID）患者的微嵌合并导致母胎移植物抗宿主病（GVHD）。然而，基于临床和免疫表型，特别是在具有亚形态突变的患者中，GVHD 和 Omenn 综合征之间的明确诊断通常很困难。研究了一名有红皮病和免疫缺陷病史的 3 岁女孩。采用全外显子组测序方法寻找致病变异体，利用TA克隆和定量荧光聚合酶链反应（QF-PCR）方法检测嵌合体或微嵌合体的存在。我们鉴定了一个纯合错义 Janus 激酶 3 突变 (JAK3, c.2324G>A, p. R775H）作为患者的一种新的致病变异体，并且母源性微嵌合体的存在被证明是其临床表现的潜在原因。研究结果强调了适当诊断方法在具有亚型 JAK3 突变的 GVHD 病例中的重要性。在分析二代测序结果时，应根据疾病的背景考虑微嵌合的可能性。