Birds of a Feather Flock Together! A Rare Case of Sporadic Inclusion Body Myositis and Rheumatoid Arthritis Treated with Rituximab.

Inclusion body myositis (IBM) is considered an inflammatory myopathy with a degenerative counterpart that is generally refractory to standard immunotherapy. We describe the case of a 47-year-old lady who had a long history of rheumatoid arthritis (RA) and subsequently developed weakness in her limbs. A muscle biopsy revealed typical features of IBM along with vasculitis. She was initiated on pulse corticosteroids followed by rituximab. The patient made a steady and marked recovery in both muscle weakness and inflammatory arthritis. Rare cases of IBM in patients with RA with favorable responses to immunotherapy have been reported before. This case demonstrates the importance of identifying coexisting autoimmune disorders and executing a long-term immunomodulatory plan.