Myositis in primary Sjögren's syndrome: clinical and pathological report.

Abstract To clarify the clinical features of myositis complicated with primary Sjögren's syndrome (SS), we studied 89 patients with Sjögren's syndrome (one male and 88 females; mean age 56.0 ± 15.31 years). Myositis was diagnosed from clinical findings, muscle enzymes, electromyographic findings, and muscle biopsy findings. Myositis was diagnosed in 5 of 89 SS patients (5.6%). One patient developed myositis 7 months after the onset of SS. The other four patients were diagnosed with myositis and SS simultaneously. Muscular weakness was mild and slowly progressive over 4-14 months (mean 8.4 months). All patients were able to walk without any assistance at the start of prednisolone therapy. Muscular enzymes were slightly elevated (from 1.5- to 12-fold). All patients tested negative for anti-Jo1 antibody and tested positive for antinuclear antibody. Anti-Ro(SSA) antibody was positive in 4/5 (90%); anti-La(SSB) was positive in 2/5 (40%). Although the clinical features of all patients met the criteria for polymyositis of Bohan, they responded well to small or moderate doses of prednisolone, which could be decreased without a recurrence of muscular weakness in all patients. Myositis with Sjögren's syndrome showed relatively moderate symptoms and responded well to prednisolone. A prospective follow-up of patients may provide further information.