Disseminated Histoplasmosis Presenting with Panniculitis and Macrophage Activation Syndrome in a Patient Undergoing Immunosuppressive Therapy for Mixed Connective Tissue Disease (MCTD).

Histoplasmosis, a fungal infection caused by Histoplasma capsulatum, is endemic in many parts of the world. However, this is not common in Japan. We herein present a unique case of military histoplasmosis in a 45-year-old female with mixed connective tissue disease (MCTD) who was receiving immunosuppressive therapy. The histological findings coupled with molecular confirmation led to final a diagnosis. This case emphasizes the diagnostic challenges associated with histoplasmosis in immunocompromised patients and underscores the importance of considering it in the differential diagnosis of any atypical presentation in rheumatic patients.