Anan Ryusuke, Akiyama Mitsuhiro, Kaneko Yuko, Kikuchi Jun, Suzuki Kazuko, Matsubara Shiro, Takeuchi Tsutomu
Division of Rheumatology, Department of Internal Medicine, Keio University School of Medicine Department of Neurology, Tokyo Metropolitan Neurological Hospital, Tokyo, Japan.
Medicine (Baltimore). 2017 Dec;96(48):e8710. doi: 10.1097/MD.0000000000008710.
Polymyositis (PM) is a type of autoimmune, inflammatory myopathy. IgG4-related disease (IgG4-RD) is a recently recognized disease entity characterized by elevated serum IgG4 levels and IgG4 plasma-cell infiltration of various organs. However, several reports have described cases of other diseases that present with those features, suggesting the importance of careful differential diagnosis. Herein, we report the first case of PM with elevated serum IgG4 levels and IgG4 plasma cells in the muscles, mimicking IgG4-RD.A 73-year-old woman visited our hospital because of proximal muscle weakness of both thighs. Her blood test showed high levels of serum creatinine kinase, aldolase, and IgG4. Magnetic resonance imaging of the thighs showed muscle edema. Needle electromyography showed findings typical of myositis. Histological analysis of her left quadriceps revealed infiltration of IgG4 plasma cells as well as CD8 T cells. Scattered necrotic and regenerating muscle fibers with no specific findings for IgG4-RD (storiform fibrosis and obliterative phlebitis) were typical for PM. We diagnosed her condition as PM and treated her with 40 mg/day of prednisolone that decreased levels of muscle enzymes and improved muscle weakness.
Our case indicated that PM could present with high serum IgG4 levels and IgG4 plasma-cell infiltration, mimicking IgG4-RD. Although the mechanism of IgG4 elevation in such PM is unclear, our case highlights the necessity to recognize that high serum IgG4 levels and IgG4 plasma-cell infiltration in organs are not specific for IgG4-RD.
多发性肌炎（PM）是一种自身免疫性炎性肌病。IgG4相关疾病（IgG4-RD）是一种最近被认识的疾病实体，其特征为血清IgG4水平升高以及各种器官的IgG4浆细胞浸润。然而，有几份报告描述了具有这些特征的其他疾病病例，提示了仔细鉴别诊断的重要性。在此，我们报告首例血清IgG4水平升高且肌肉中有IgG4浆细胞的PM病例，该病例酷似IgG4-RD。一名73岁女性因双侧大腿近端肌无力前来我院就诊。她的血液检查显示血清肌酸激酶、醛缩酶和IgG4水平升高。大腿磁共振成像显示肌肉水肿。针极肌电图显示出典型的肌炎表现。对其左股四头肌的组织学分析显示有IgG4浆细胞以及CD8 T细胞浸润。散在的坏死和再生肌纤维，无IgG4-RD的特异性表现（席纹状纤维化和闭塞性静脉炎），这是PM的典型表现。我们将她的病情诊断为PM，并给予她40毫克/天的泼尼松龙治疗，这降低了肌肉酶水平并改善了肌无力。
我们的病例表明PM可表现为血清IgG4水平升高和IgG4浆细胞浸润，酷似IgG4-RD。尽管此类PM中IgG4升高的机制尚不清楚，但我们的病例强调了认识到血清IgG4水平升高和器官中IgG4浆细胞浸润并非IgG4-RD所特有的必要性。
