IS Case 349: Adrenal histoplasmosis
2009 URMC Imaging Sciences
Publication Date: 2009-11-09
Contrast enhanced CT demonstrates a 4.8 x 3.1 cm left adrenal mass and a 1.2 cm right adrenal nodule. There are multiple enlarged mesenteric nodes. At MRI the left adrenal mass enhances diffusely, is T2 hyperintense despite fat saturation technique, and does not show a drop in signal on the out-of-phase sequence.
Histoplasma capsulatum is a dimorphic fungus that flourishes in regions of the United States like the Mississippi and Ohio River valleys, as well as other humid parts of the world where soil is contaminated with bird droppings or in caves rife with bat guano . Histoplasmosis primarily involves the lungs, however every organ system can be affected. The infectious microconidia are inhaled when the soil is agitated and the host immune system may contain the infection through fibrosis or by forming granulomas especially in the lung parenchyma or lymph nodes. Over time the granulomas may caseate and calcify. Alternatively, H. capsulatum can proliferate and effectively evade the host response when ingested by cells of the reticuloendothelial system . The resultant asymptomatic fungemia lasts until immunosupression permits reactivation of disease. This is the likely scenario for the above patient who was taking immunosuppressive medication.
Findings that may occur with high incidence in disseminated disease are nonspecific and include bilateral adrenal masses often with central necrosis and associated adrenal insufficiency, hepatomegaly, splenomegaly (some with diffuse hypoattenuation), retroperitoneal and mesenteric adenopathy [2, 3]. The very young, the elderly and immunosupressed patients are at high risk of dissemination. Differential considerations for bilateral adrenal masses may include metastasis, lymphoma, hemorrhage, and other granulomatous infections like tuberculosis, cryptococcosis, and blastomycosis.
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