Overlap Syndromes in Polymyositis and Dermatomyositis

다발근육염과 피부근육염에서 관찰된 중첩증후군

Background: The term "overlap syndromes" designates a group of diseases in which polymyositis (PM) or dermatomyositis (DM) is associated with some other disorders of connective tissues. The aim of this study was to delineate the clinical features, laboratory findings, and outcome of treatment of "overlap syndromes" Methods: We analyzed the medical records of 16 patients (PM in 10, DM in 6) with well documented "overlap syndromes" between 1997 and 2004. The diagnosis was made when the criteria for two different disorders were fulfilled. Results: All patients were female. Age of onset ranged from 14 to 52 years (mean 29.8 years) with peak incidence in the third and fourth decades. Systemic lupus erythematosus (SLE) was associated in 10, systemic sclerosis in 7, and rheumatoid arthritis in 3 patients. Four of the patients had two different connective tissue diseases simultaneously. The characteristic clinical features were muscle weakness, arthralgia, Raynaud's phenomenon, and myalgia. In laboratory tests, creatine kinase (CK), lactic dehydrogenase (LDH), and transaminases were usually abnormal. Positive antinuclear antibody (ANA), rheumatoid factor (RF), and cryoglobulin were found in 100%, 69%, and 67% of the patients, respectively. Needle electromyography (EMG) showed abnormal findings compatible with myopathy in 15 patients. The pathology of muscle biopsy from 14 patients revealed findings compatible with inflammatory myopathy. Glucocorticoids were administered to 15 patients. The muscle strength improved in all the treated patients, which was well correlated with repeat CK level and EMG findings. Conclusions: The presence of autoantibodies such as ANA, RF, and cryoglobulin in patients with PM or DM highly suggests the possibility of an overlap syndromes. These syndromes reveal a strong female predominance. The myositis associated with them usually shows a good response to glucocorticoids treatment.