OSTEOARTICULAR INFECTION CAUSED BY HISTOPLASMA CAPSULATUM

Osteoarticular fungal infections are chronic, debilitating, and challenging diseases with considerable morbidity. Tenosynovitis caused by Histoplasma capsulatum is very uncommon: only seven confirmed reports exist in the literature. We report the case of a 53-year-old woman with hypertension and a history of chronic synovitis of the right knee for more than 18 months, during which she received two corticosteroid injections. She sought care in November 2022 with erythema of the right lower limb associated with ipsilateral knee pain. She had mild leukocytosis with neutrophilia and normal inflammatory markers. Knee MRI showed patellar chondropathy with bone marrow edema in the medial femoral condyle; periarticular marrow signal changes with an edema pattern at the margins of the medial and lateral tibial condyles; moderate joint effusion; and synovial lining thickening and heterogeneous signal, suggesting synovitis. Arthrocentesis with biopsy was performed and empirical ampicillin-sulbactam was given for 7 days; she was discharged for outpatient follow-up. Biopsy showed chronic granulomatous synovitis with multinucleated giant cells, areas of necrosis, and a large number of yeasts suggestive of H. capsulatum . She was admitted in December 2022 with worsening knee pain, underwent surgical debridement, material collection (culture grew H. capsulatum ), and started itraconazole 200 mg every 8 hours. She was discharged on the same regimen but was re-admitted 2 months later with clinical, radiological, and laboratory worsening, though cultures were negative. She underwent another surgical debridement and started liposomal amphotericin B; she completed 4 weeks and was discharged on itraconazole. One month later, she returned with moderate joint effusion with synovitis and pericapsular collections, increased bone marrow edema focus, and worsening pain. She underwent surgical debridements, synovectomy, and vacuum-assisted dressing, and received liposomal amphotericin B for 90 days. She was discharged on itraconazole in September 2023, her last hospitalization. She remains under outpatient follow-up with an infectious disease specialist, continues itraconazole, has good clinical evolution, and has not required further admissions. Histoplasma tenosynovitis is a rare cause of inflammatory arthritis, and early diagnosis is essential for successful treatment.