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

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.