Ryan Meghan E, Cortez Daniel, Dietz Kelly R, Karachunski Peter, Binstadt Bryce A
Department of Pediatrics, Division of Rheumatology, Allergy & Immunology, University of Minnesota, Minneapolis, USA.
Department of Pediatrics, Division of Cardiology, University of Minnesota, Minneapolis, USA.
BMC Rheumatol. 2021 Apr 2;5(1):8. doi: 10.1186/s41927-021-00180-9.
Patients with idiopathic inflammatory myopathy and autoantibodies directed against melanoma differentiation-associated protein 5 (MDA5) characteristically have interstitial lung disease, severe cutaneous involvement, arthritis, and relatively mild myositis. Cardiac involvement in idiopathic inflammatory myopathy can occur and has been associated with anti-signal recognition particle and anti-polymyositis-scleroderma autoantibodies, but not with anti-MDA5 autoantibodies.
A 14-year-old male presented with weakness, second-degree heart block, arthritis, and hematologic cytopenias. Imaging and biopsies confirmed the diagnosis of juvenile idiopathic inflammatory myopathy, and he had high titer anti-MDA5 autoantibodies. There were no cutaneous or pulmonary abnormalities. While on prednisone and methotrexate, the patient's heart block improved from second- to first-degree and the cytopenias resolved. Persistent myositis prompted the addition of intravenous immunoglobulin. Seven months into the disease course, the arthritis and myositis are in remission and the patient is no longer taking corticosteroids.
We report a novel case of a patient with juvenile idiopathic myositis who lacked the typical cutaneous and pulmonary findings associated with anti-MDA5 positivity, but who had cardiac conduction defects. This report broadens the clinical spectrum of anti-MDA5-associated inflammatory myopathy.
患有特发性炎性肌病且有针对黑色素瘤分化相关蛋白5（MDA5）自身抗体的患者，其特征表现为间质性肺病、严重皮肤受累、关节炎以及相对较轻的肌炎。特发性炎性肌病可出现心脏受累，且与抗信号识别颗粒和抗多发性肌炎-硬皮病自身抗体有关，但与抗MDA5自身抗体无关。
一名14岁男性出现肌无力、二度心脏传导阻滞、关节炎和血液系统血细胞减少。影像学检查和活检确诊为青少年特发性炎性肌病，且他有高滴度抗MDA5自身抗体。无皮肤或肺部异常。在使用泼尼松和甲氨蝶呤治疗期间，患者的心脏传导阻滞从二度改善为一度，血细胞减少症得到缓解。持续性肌炎促使加用静脉注射免疫球蛋白。病程7个月时，关节炎和肌炎缓解，患者不再服用皮质类固醇。
我们报告了一例青少年特发性肌炎患者的新病例，该患者缺乏与抗MDA5阳性相关的典型皮肤和肺部表现，但有心脏传导缺陷。本报告拓宽了抗MDA5相关炎性肌病的临床谱。
