Neurological Institute of Jiangxi Province and Department of Neurology, Jiangxi Provincial People's Hospital, Nanchang University, Jiangxi, PR China.
Int J Neurosci. 2020 Nov;130(11):1178-1181. doi: 10.1080/00207454.2020.1730366. Epub 2020 Feb 19.
Myasthenia gravis (MG) is an autoimmune disease and closely related to thymoma. Inflammatory myopathy may accompany with other autoimmune diseases. However, concurrence of inflammatory myopathy and MG is very rare. Necrotizing autoimmune myopathy (NAM), a rare form of inflammatory myopathy, is characterized by necrosis and regeneration of myocytes in proximal muscles without significant inflammation. The aim of the study was to report a rare case of NAM and concomitant thymoma-associated MG after thymectomy. A 27-year-old female patient presented with muscle soreness and weakness in four limbs. Eyelid fatigue and neostigmine tests were negative, and no ptosis was found but the electromyographic examination (EMG) showed myogenic damage and a gradual decrease in the amplitude (20%) of EMG activities evoked by repetitive electrical stimulation. Antibodies against AChR and increased titer of creatine kinase were detected and plaque-like signals in both legs were found in magnetic resonance imaging. Myositis-related antibodies were negative but necrotic myocytes without inflammatory cell infiltration, and MHC-1 positive muscle fibers were found in muscle biopsy. Pathological examination confirmed anterior mediastinal B2 type thymoma. Five weeks after thymectomy, she started to show typical MG symptoms. No recurrence of thymoma was found but immunoassay showed a higher titer of AChR-Ab. Myositis-related antibodies negative necrotizing autoimmune myopathy (NAM) was reported to be associated with thymoma-associated MG. The patient showed symptoms related NAM but developed MG-related symptoms only after thymectomy. The mechanisms for the phenomena may be related to immune dysfunction associated with thymoma.
重症肌无力（MG）是一种自身免疫性疾病，与胸腺瘤密切相关。炎性肌病可能伴有其他自身免疫性疾病。然而，炎性肌病和 MG 同时发生非常罕见。坏死性自身免疫性肌病（NAM）是一种罕见的炎性肌病，其特征是近端肌肉的肌细胞坏死和再生，而无明显炎症。本研究旨在报告一例罕见的 NAM 病例，并在胸腺切除术后伴发胸腺瘤相关 MG。一名 27 岁女性患者出现四肢肌肉酸痛和无力。眼睑疲劳和新斯的明试验均为阴性，未发现上睑下垂，但肌电图检查（EMG）显示肌源性损伤，并且由重复电刺激诱发的 EMG 活动幅度逐渐降低（20%）。检测到乙酰胆碱受体抗体和肌酸激酶升高，磁共振成像显示双腿出现斑块样信号。肌炎相关抗体阴性，但肌肉活检显示无炎症细胞浸润的坏死肌细胞和 MHC-1 阳性肌纤维。病理检查证实为前纵隔 B2 型胸腺瘤。胸腺切除术后 5 周，她开始出现典型的 MG 症状。未发现胸腺瘤复发，但免疫测定显示乙酰胆碱受体抗体滴度升高。报道称肌炎相关抗体阴性的坏死性自身免疫性肌病（NAM）与胸腺瘤相关的 MG 相关。该患者表现出与 NAM 相关的症状，但仅在胸腺切除术后才出现与 MG 相关的症状。这些现象的机制可能与与胸腺瘤相关的免疫功能障碍有关。
