Muscle-specific tyrosine kinase antibody (MuSK-Ab) and acetylcholine receptor antibody (AChR-Ab) coexistence in myasthenia gravis (MG) is very rare. In this report, two children with AChR-Ab switching to double antibody positive MG (DP-MG) or MuSK-Ab positive MG (MuSK-MG) are described. Six similar cases were found in the literature via online database search. Therefore, this study describes eight patients in total, six female and two male. The average age of onset was 7.25 ± 5.95 years. Four AChR-MG patients switched to DP-MG with no known precipitating factor and four switched after thymectomy (two to MuSK-MG and two to DP-MG). After the serological switch, the patients transitioned to the phenotype of MuSK-MG and responded poorly to cholinesterase inhibitors and well to corticosteroids and plasma exchange.

中文翻译：

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两名儿童 AChR 重症肌无力改用 MuSK 或双抗体阳性重症肌无力及文献复习

肌肉特异性酪氨酸激酶抗体（MuSK-Ab）和乙酰胆碱受体抗体（AChR-Ab）共存在重症肌无力（MG）中非常罕见。在这份报告中，描述了两个 AChR-Ab 转换为双抗体阳性 MG (DP-MG) 或 MuSK-Ab 阳性 MG (MuSK-MG) 的儿童。通过在线数据库搜索在文献中发现了六个类似的案例。因此，本研究共描述了八名患者，六名女性和两名男性。平均发病年龄为 7.25 ± 5.95 岁。四名 AChR-MG 患者在没有已知促发因素的情况下改用 DP-MG，四名在胸腺切除术后改用（两个改用 MuSK-MG，两个改用 DP-MG）。血清学转换后，患者转变为 MuSK-MG 表型，对胆碱酯酶抑制剂反应不佳，对皮质类固醇和血浆置换反应良好。