Infliximab-treated patient develops delayed primary cutaneous histoplasmosis, initially misdiagnosed

Patients with rheumatoid arthritis (RA) often receive immunosuppressive therapies, including TNF-alpha inhibitors like infliximab, which can increase susceptibility to opportunistic infections. Primary cutaneous histoplasmosis (PCH), a rare fungal infection caused by Histoplasma capsulatum, presents with polymorphic skin manifestations, making diagnosis challenging and often leading to misdiagnosis. This case highlights the diagnostic gap for unusual infections in immunocompromised individuals, where standard treatments for common conditions like cellulitis fail.

This case report describes a woman in her 60s with rheumatoid arthritis receiving infliximab and long-term prednisone. She presented with progressive, non-healing lesions on her left forearm. Initially, the lesions were treated as cellulitis without improvement. Further investigation involved a biopsy of the persistent lesions, followed by fungal culture to identify the causative pathogen. The primary endpoint was the accurate diagnosis and subsequent clinical resolution of the skin lesions.

After initial misdiagnosis and failed cellulitis treatment, further investigation confirmed a diagnosis of primary cutaneous histoplasmosis (PCH). The causative agent was identified as Histoplasma capsulatum through fungal culture. This confirmed the presence of an atypical fungal infection in an immunocompromised patient. Systemic antifungal therapy was initiated following the definitive diagnosis. > The patient experienced clinical resolution of the progressive, non-healing lesions on her left forearm after receiving appropriate systemic antifungal treatment.