Brachio-cervical inflammatory myopathies: clinical, immune, and myopathologic features.

OBJECTIVE: To characterize patients with inflammatory myopathies who present with weakness in the proximal regions of the arms.
METHODS: Clinical, laboratory, and myopathologic features were evaluated in 10 patients, identified consecutively over 12 years, with inflammatory myopathies and weakness that was most severe in the proximal regions of the arms. The features of these brachio-cervical inflammatory myopathy (BCIM) syndromes were compared with those of other inflammatory and immune-mediated myopathies evaluated during the same period.
RESULTS: Patients with BCIM developed progressive weakness at ages 24-82 years (mean +/- SD age 55 +/- 9 years). Posterior neck weakness occurred in 60% of patients, while motor neuron disease was the referring diagnosis in 30%. All patients had other systemic autoimmune disorders, including myasthenia gravis (40%) and rheumatoid arthritis (20%). Antinuclear antibodies were present in all patients. Serum creatine kinase levels were usually moderately high (mean 910 IU/liter). Active myopathy was identified in muscle biopsy samples from the patients. Focal collections of mononuclear cells, some predominantly B cells, were present in perivascular and perimysial regions. MxA- and CD123-positive dendritic cells were present in the endomysium. C5b-9 components of complement were present diffusely in endomysial connective tissue. Most patients improved in strength after receiving corticosteroids.
CONCLUSION: Patients with BCIM syndromes have progressive weakness in the proximal regions of the arms and neck. The predominant myopathologic findings are active myopathy, C5b-9 staining of endomysium, focal perivascular and perimysial inflammation, often with a prominent B cell component, and endomysial dendritic cells. Corticosteroid treatment of BCIM is often followed by improvement in strength.