ABSTRACT
Background: Arthritis by Paracoccidioides brasiliensis is a remarkably unusual etiology of infectious joint disease. While osseous lesions can be present in systemic disease, intra-articular-restricted disease without typical lung or lymph node involvement is mostly anecdotal1,2. Objectives: We hereby describe a case of this fungal arthritis in a patient with rheumatoid arthritis (RA) without signifcant immunosuppression. Methods: Patient records review. Written informed consent was obtained. Results: A 65-year-old female Brazilian patient with a 35-year history of seropositive RA complained of a painful knee edema for the last three weeks. Skin surrounding the joint was erythematous, warm, and tender to the touch, which initially raised the suspicion of cellulitis. She had already received a 10-day course of amoxicillin-clavulanate, with no improvement. C-reactive protein was 17.8 mg/L, rest of blood chemistry panel was within reference range. Point-of-care ultrasound revealed joint effusion, and a diagnostic arthrocentesis was performed. Synovial fluid was slightly turbid, with 10,100 cells per mm3, of which 80% were lymphocytes. Cultures for bacteria and mycobacteria yielded negative results, but culture for fungi detected growth of P. brasiliensis. The patient had been solely on prednisone 5 mg once daily for the last year, given that, due to covid-19 pandemics, she lost regular follow-up and abandoned treatment with immunosuppressants. Aside from mild RA-related interstitial lung disease, she had no other comorbidity. She denied local trauma to the knee, which made hematogenous dissemination of the fungi the most probable source. Comprehensive work-up to search for organic involvement of paracoccid-ioidomycosis, including chest computed tomography and transthoracic echocardiogram, did not evidence any visceral compromise. Voricona-zole 200mg t.i.d. was started, with good response. Three months after the beginning of the azole, tofacitinib was started for moderate RA disease activity, which also responded satisfactorily. Repeat arthrocentesis and synovial biopsy were performed eight months after the start of antifun-gal treatment, the former being normal (770 cells per mm3, negative cultures), and the later only demonstrating non-specific chronic synovitis with fibrosis. Conclusion: We reported an exceedingly rare presentation of P. brasiliensis infection with exclusive joint involvement.