A Rare Case of Multicentric Reticulohistiocytosis with Concurrent Rheumatoid Arthritis.

Multicentric reticulohistiocytosis (MRH) is a rare multisystem macrophage disorder of unknown etiology characterized by papulonodular skin and mucosal lesions, rapidly progressive erosive symmetric polyarthritis, and inflammation of internal organs. Most often, it is misdiagnosed as rheumatoid arthritis (RA). Here, we report the case of a 60-year-old woman found to have features of both MRH and RA with positive rheumatoid factor and high titer of anti-cyclic citrullinated peptide antibody in serum. It was confirmed by a histopathology of skin lesions, which showed diffuse histiocytic infiltrate with multinucleated giant cells. She was treated with methotrexate, hydroxychloroquine, corticosteroids, and nonsteroidal anti-inflammatory drugs and bisphosphonate.