Synovitis due to Histoplasma capsulatum: a case series and literature review.

Musculoskeletal manifestations of Histoplasma capsulatum infection are uncommon but can mimic inflammatory arthritis. Early diagnosis of this complication is of critical importance in the era of potent immunosuppression for rheumatologic diseases. We conducted a retrospective chart review for patients with histoplasmosis and tenosynovitis, synovitis, or arthritis, diagnosed and treated at our institution between January 1, 2000, and December 31, 2019. We also reviewed the relevant literature. Four patients with biopsy-proven, culture-proven histoplasma tenosynovitis were identified at our institution. All four patients had wrist or hand involvement in an asymmetric pattern, and one patient had lower extremity involvement as well. Two patients were not immunocompromised at baseline. One patient underwent a lengthy evaluation and received immunosuppression for 4 years without improvement prior to the diagnosis of histoplasmosis. Histoplasma serologic tests varied among patients with localized infection. Pathologic findings revealed non-caseating granulomatous inflammation. Three patients recovered after 6-12 months of antifungal treatment. One patient still had recurrent infection despite 20 months of treatment. Histoplasma tenosynovitis and synovitis are rare causes of inflammatory arthritis. Infectious causes should be considered and carefully evaluated when patients present with asymmetric oligoarthritis. Early recognition is crucial for successful treatment, especially in patients with concomitant rheumatologic diseases receiving immunosuppressive treatment.