探讨多发性肌炎（PM）和皮肌炎（DM）的临床特点，为提供临床诊疗依据。

对1998年1月至2018年3月苏州大学附属第三医院风湿免疫科收治的308例PM和DM患者的临床资料进行回顾性分析。

PM首发症状以肌无力多见，占92.8%，DM以皮疹为首发，占66.7%。DM合并间质性肺病、伴发肿瘤的发生率较PM高，差异具有统计学意义（37.5% vs 69.8%，χ²=20.790，P<0.01；4.3% vs 95.6%，χ²=6.957，P<0.01）。PM组肌酸激酶（CK）及CK-MB水平均高于DM组，差异具有统计学意义（t=-6.684，P=0.000；t=-6.964，P=0.000）。PM的病理改变以肌纤维变性、结缔组织增生为主，DM以束周萎缩、空泡变性及肌束间、血管周围炎细胞浸润为主。随访243例患者（PM 48例，DM 195例），随访期内DM病死率高于PM（18.7% vs 7.1%，χ²=4.392，P=0.036）。死亡主要原因为肺部感染及肿瘤，

PM和DM在临床表现、肌酶、肌活检病理及病死率上均有不同，DM易合并间质性肺病继发感染和肿瘤，病死率高。

To investigate the clinical characteristics of patients with polymyositis (PM) and dermatomyositis (DM) to provide a basis for clinical diagnosis and treatment of these conditions.

Three hundred and eight patients with PM and DM admitted to the Department of Rheumatology and Immunology of the Third Hospital Affiliated to Soochow University were collected from January 1998 to March 2018, and the clinical manifestations, muscle enzymes, electromyogram (EMG), muscle biopsy and treatment outcome were retrospectively analyzed.

The most common initial symptom of PM was muscle weakness, accounting for 92.8% of all cases, while rash was the most common initial presentation in DM cases, accounting for 66.7%. The incidence of interstitial lung disease (ILD) (69.8% vs 37.5%, χ²=20.790, P=0.000) and concomitant tumors (95.6% vs 4.3%, χ²=6.956891, P=0.008350) was significantly higher in DM patients than in PM patients. The percentages of PM patients with elevated CK (t=-6.684, P=0.000) and CK-MB (t=-6.964, P=0.000) were significantly higher than those of DM patients. The pathological changes in PM patients mainly consisted of myofiber degeneration and connective tissue hyperplasia, while those in DM patients were mainly characterized by peripapillary atrophy, vacuolar degeneration and inflammatory cell infiltration between the intermuscular and perivascular tissues. Follow-up was performed in 243 patients. The mortality of DM was higher than that of PM (18.7% vs 7.1%, χ²=4.392, P=0.036). The main causes of death were pulmonary infections and tumors.

PM and DM patients are different in clinical manifestations, muscle enzymes, pathology and mortality. Infection secondary to ILD and tumor are more common in DM, with a higher mortality rate, than in PM.