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Myositis uncommon, treatable in many patients with primary Sjögren’s syndrome
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The prevalence of myositis in patients with primary Sjögren’s syndrome is low and mostly presents as an overlapping syndrome that usually responds to treatment with immunosuppressants, according to the results of a study of patients from five rheumatology centers in Italy.
Researchers reviewed the demographic, serological and treatment records of 1,320 patients with primary Sjögren’s syndrome (pSS) in an observational, retrospective, cross-sectional study. Patients with pSS and additional symptoms of myositis were identified using treatment records and Bohan and Peter classification criteria for inflammatory myopathy. The identified patients reported muscle weakness, sometimes associated with severe pain related to grasping or high levels of creatine phosphokinase (CPK). Electromyography (EMG) was performed and muscle biopsies were collected and reviewed by one pathologist.
Seventeen patients with myositis were identified among the 1,320 patients with pSS. Thirteen of the 17 patients had increased serum CPK. Of 14 patients with available EMG data, 13 had signs of muscle damage. Among 13 of 17 patients with a positive antinuclear antibody test, 12 were anti-SSA-positive, three were positive for anti-Jo-1 antibodies and one was also anti-RNP-positive. Ten patients met at least three of the criteria for inflammatory myopathy.
Muscle biopsies were normal in three of 13 patients with biopsy data available. Four patients had scattered hypotrophic fibers without inflammatory infiltrates, and one patient showed muscle fiber necrosis, myophagocytosis and rimmed vacuoles upon staining, suggestive of inclusion body myositis, according to the researchers. Five had endomysial lymphocytic infiltrate and muscle fiber necrosis.
All patients were treated with 1 mg prednisone equivalent for 3 days followed by a conventional disease-modifying anti-rheumatic drug (DMARD), including methotrexate, hydroxychloroquine, azathioprine or cyclosporine. Intravenous immunoglobulin and Rituxan (rituximab, Genentech) were used in three patients and two patients, respectively. Most patients remained in remission, and seven patients remained on ongoing treatment with hydroxychloroquine with partial improvements, according to the researchers. – by Shirley Pulawski
Disclosure: The researchers report no relevant financial disclosures.
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