Multicentric reticulohistiocytosis with hydrarthrosis in both knee joints: Disease stabilization with synovectomy, and medication with a steroid and low-dose methotrexate

Multicentric reticulohistiocytosis is a rare systemic disease characterized by the infiltration of histiocytes and multinucleated giant cells with cutaneous nodules, and severe destructive arthritis. It is commonly the peripheral joints which are affected, and therefore symptoms in large joints have not been fully investigated. We describe the case of a 44-year-old woman with multicentric reticulohistiocytosis, who was suffering from swelling in both knee joints and cutaneous nodules, in addition to arthritis in the elbow, hip, and peripheral joints. Magnetic resonance imaging of both knee joints showed hydrarthrosis associated with a tumor-like overgrowth of synovial tissue. These symptoms were reduced following a resection of the synovial tissue and subsequent medication with prednisone and low-dose methotrexate. It should be noted that swelling in the knee joints can be one of the symptoms caused by multicentric reticulohistiocytosis, in addition to cutaneous nodules and arthritis in the peripheral joints. Resection of synovial tissue, and medication with prednisone and low-dose methotrexate were effective in the present case.