MON-356 Disseminated Histoplasmosis Mimicking Metastatic Rectal Cancer

Background: Various etiologies account for bilateral adrenal masses including infections, malignancies and adrenal hemorrhage. Accurate diagnosis is needed to provide the best care for the patient. Clinical case: A 63-year-old Thai male patient with locally advanced rectal cancer was treated with concurrent chemoradiotherapy in 2013. He had been followed up at the oncology clinic regularly after his cancer treatment and there was no evidence of cancer recurrence. In early 2018, he presented with anorexia, weight loss and non-productive cough. His chest X-ray showed the presence of patchy opacity of the left lung. The CT of the chest and whole abdomen revealed multiple bilateral pulmonary nodules, bilateral adrenal masses (sized 3.4x5.4 and 4.3x5.5 cm) and an enlarged spleen without definite space-taking lesion. At that time, he was diagnosed with recurrent rectal cancer and presented at the emergency department due to acute diarrhea and hypotension. Multiple discrete umbilicated papules at face, tongue and hands were noted on the physical examination. Hypotension persisted after volume resuscitation. Random cortisol level was 11 µg/dL before hydrocortisone was initiated. Wright stain of the skin lesion showed intracellular yeast-like organism and culture of the skin biopsy showed Histoplasma capsulatum. Bone marrow involvement from the same organism was also documented. After reviewing his clinical course, the diagnosis was compatible with disseminated histoplasmosis (skin, pulmonary, adrenal, spleen and bone marrow involvement). He was treated with amphotericin B for 3 weeks before switching to itraconazole. Two months after antifungal treatment, CT showed increased in size and number of multiple hypodensity lesions at spleen. Therefore, bilateral adrenalectomy with splenectomy was performed without complication. Pathological findings showed diffuse necrotizing areas with surrounded histiocytes, foamy macrophages and multinucleated giant cells in both adrenal glands and spleen. GMS showed presence of numerous small ovoid yeasts, compatible with histoplasmosis. This patient had been doing well with his long-term treatment with itraconazole and glucocorticoid replacement. Conclusion: This was the case of disseminated histoplasmosis whose presentation mimicked metastatic rectal cancer. Misdiagnosis caused delay in the diagnosis and treatment of adrenal insufficiency. References: Koene RJ, Catanese J, Sarosi GA. Adrenal hypofunction from histoplasmosis: A literature review from 1971 to 2012. Infection. 2013;41:757-9.