The Clinical and Pathological Characteristics of Polymyositis Using ENMC Diagnostic Criteria / 대한류마티스학회지

ABSTRACT

OBJECTIVE: Polymyositis (PM) has known to be the most common type of idiopathic inflammatory myopathy (IIM). However, recent immunopathological studies demonstrated that PM was overdiagnosed previously due to suboptimal classification system. Using newly proposed classification system, we investigated the frequency, clinical and pathological characteristics of PM. METHODS: Among the patients diagnosed as IIM during past 6 years, we classified a 'definite' or 'probable PM' using the European Neuromuscular Center (ENMC) diagnostic criteria. The findings of clinical, laboratory and pathological findings were analyzed. Response to treatment was assessed at 6 months after treatment. RESULTS: Of total 97 cases with IIM, twenty-three cases (24%) were satisfactory to the diagnostic criteria for PM (definite=5 and probable=18). Most cases were young adults, and female predominance was found. All cases showed proximal muscle weakness, and about two-thirds of patients showed extramuscular manifestation. One (4%) had breast cancer, and accompanying connective tissue disorders (CTDs) were found in 3 cases (13%), two of which had systemic sclerosis. Interstitial pneumonia was found in one case (4%). All cases showed marked elevation of serum creatine kinase level. On muscle biopsy, there were endomysial mononuclear cell infiltrations in all cases. Three-fourths of patients responded to immunosuppressant therapy (74%). CONCLUSION: Using ENMC criteria, the frequency of PM was lower than that had been reported previously. The results of clinical characteristics, response to therapy and clinical outcome were similar to the previous reports. However, association of malignancy or CTDs was low in PM.