Disseminated histoplasmosis presenting as primary adrenal insufficiency in an immunocompetent host in the United States: a case report

BACKGROUND: Histoplasma capsulatum is a dimorphic fungus that is mostly seen in immunocompromised individuals. Its presentation ranges from acute pulmonary infections to disseminated disease that can affect multiple organ systems, including the adrenal glands. Dissemination is uncommon in immunocompetent hosts, but involvement of the adrenal glands is largely reported in those with a competent immune system. Subsequent primary adrenal insufficiency is a rare finding, especially in the United States with only two such cases reported before. CASE PRESENTATION: We report the case of 62-year-old immunocompetent Caucasian man with a history of exposure to farm animals and bats who was referred to the emergency department for weight loss, fatigue, decreased appetite, and hyponatremia. Computed tomography (CT) imaging demonstrated bilateral adrenal thickening with no focal nodules. Low serum cortisol, elevated adrenocorticotropic hormone, and an absent cortisol response to cosyntropin confirmed primary adrenal insufficiency. Biopsy of the adrenal gland revealed caseating granulomas and fungal elements consistent with Histoplasma species. Multiple scattered pulmonary nodules were also observed on chest CT, though there were no accompanying pulmonary symptoms. The patient was initiated on isavuconazole for one year with the treatment currently underway. CONCLUSION: Clinicians should consider histoplasmosis in immunocompetent individuals with primary adrenal insufficiency and negative 21-hydroxylase antibodies. Immunosuppression and pulmonary symptoms should not be considered necessary prerequisites for it to be a differential diagnosis.