Rheumatoid arthritis-like active synovitis with T-cell activation in a case of idiopathic multicentric Castleman disease: A case report.

Idiopathic multicentric Castleman disease (iMCD) is a systemic disease with multiple regions of lymphadenopathy and systemic symptoms and associated with rheumatoid arthritis (RA) and collagen diseases. However, few reported have described the coexistence of iMCD and RA and the mechanisms by which iMCD induces arthritis remain elusive. We experienced a rare case of iMCD, wherein the patient exhibited symptoms of polyarthritis with high-grade fever. A 34-year-old woman was admitted to our hospital for further evaluation of a high fever with polyarthritis. The levels of both rheumatoid factor and anticitrullinated protein antibody were negative. F-fluorodeoxyglucose/positron emission tomography-computed tomography showed lymphadenopathy with increased fluoro-2-deoxy-D-glucose uptake. Magnetic resonance imaging and musculoskeletal ultrasonography revealed active synovitis in the hands which was consistent with RA. We diagnosed iMCD based on human herpesvirus 8 negativity, HIV negativity, systemic lymphadenopathy, and pathologic findings of the lymph nodes. The patient did not satisfy the 2010 American College of Rheumatology and European League Against Rheumatism classification criteria for RA. Cytokine assay showed elevated serum levels of interleukin-17 and CXCL10, comparable to those in patients with RA. We administered 15 mg/d of predonisolone. After this treatment, the patient's symptoms showed improvement. As of this writing, we tapered the prednisolone to 7.5 mg/d, and the patient's remission has been maintained for >4 months. The present case suggests that RA-like active synovitis may coexist in iMCD, resulting from aberrant T-cell activation and histologic examination using lymph node biopsy may help enable early diagnosis of iMCD.