Severe proximal myopathy and mononeuritis multiplex in rheumatoid arthritis: manifestations of rheumatoid vasculitis.

Vascular injury is considered to be a key finding in the pathogenesis of rheumatoid arthritis (RA). Manifestations are varied depending on the vessel size and the organ system involved. Vasculitis leading to symptomatic inflammatory myositis is a rare complication of RA. We describe a 62-year-old man with seropositive erosive RA of 1-year duration, who presented with severe proximal weakness and mononeuritis multiplex. His joint disease was clinically mild at the time of presentation. Creatine kinase was normal and the electromyogram did not suggest myopathy. However, muscle biopsy revealed extensive small vessel vasculitis and severe inflammatory myositis. This report emphasizes the importance of fully evaluating patients with RA who present with proximal myopathy. The myopathy in our patient was not related to active joint disease, disuse atrophy, or complication of therapy. Rheumatoid vasculitis leading to myositis is a rare and not well-recognized complication of RA for which aggressive immunosuppressive therapy is warranted.