Upper extremity Histoplasma capsulatum treatment with isavuconazole

Extrapulmonary Histoplasma capsulatum infections in the immunocompetent population are rare and pose a diagnostic challenge. Upper extremity histoplasmosis without a primary lung infection is uncommon. It is possible to acquire it by inadvertent trauma with direct inoculation. Our case describes an immunocompetent patient with progressive swelling with minimal pain in the wrist associated with a small puncture wound on the left dorsal forearm. The initial workup failed to identify a specific etiology. For the following six weeks, the patient experienced progressive worsening of symptoms, warranting a referral to an orthopedic hand surgeon. Left lower extremity magnetic resonance imaging (MRI) findings were non-specific. The surgeon performed a surgical exploration and debridement with the excision of hypertrophic tissue. Initial stains showed a granulomatous tissue but did not reveal an organism; however, a month later, mold was identified on the growth medium. The patient was initiated in isavuconazole empiric therapy. Four weeks later, a matrix assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) confirmed the diagnosis as Histoplasma capsulatum. The patient had clinical remission with isavuconazole used as the United States Food and Drug Administration (FDA) off label use.