S5566 Periaortic Histoplasmoma Causing Hepatic Artery Stenosis in a Liver Transplant Recipient

Introduction: Histoplasmomas are mycotic granulomatous nodules caused by the fungus Histoplasma capsulatum that present primarily as pulmonary nodules. We present a rare case of a histoplasmoma manifesting as a periaortic mass causing hepatic artery stenosis in a liver transplant recipient. Case Description/Methods: A 65-year-old woman 2 years status post deceased donor liver transplantation for hepatitis C-related decompensated cirrhosis and hepatocellular carcinoma with excellent graft function undergoes routine surveillance liver ultrasound. Labs were normal: aspartate aminotransferase 15 U/L (8-33), alanine aminotransferase 27 U/L (7-56), total bilirubin 0.3 mg/dL (0.2-1.1), alkaline phosphatase 123 IU/L (45-117), and international normalized ratio 1 (0.8-1.2). Abdominal imaging demonstrated low resistive indices of the hepatic arteries with a parvus tardus pattern suggestive of anastomotic narrowing. Computed tomography (CT) angiography revealed a 2.6 cm periaortic soft tissue mass causing severe stenosis of the proximal vascular anastomosis from the distal abdominal aorta into the hepatic artery. The mass was biopsied and histology demonstrated small, uniform, oval yeasts with narrow-based budding and nuclei clustered within histiocytes consistent with a histoplasma infection. Patient was initially treated with itraconazole but due to the lack of improvement in size and concern for vascular anastomosis compromise, patient underwent hepatic artery stenting. She was transitioned to amphotericin B due to concern for reactivation in the setting of immunosuppression with ultimate resolution of histoplasmoma. Discussion: H. capsulatum is a ubiquitous and dimorphic fungus which is transmitted via inhalation of spore-containing dusts or aerosols. Although rare, chronic infection can lead to histoplasmoma formation, a slow-growing nodule that can be difficult to distinguish from malignancy or tuberculoma. The gold standard for diagnosis is biopsy which will show H. capsulatum under GMS or PAS stains and granulomatous inflammation. While histoplasmomas classically present as solitary pulmonary nodules, our case highlights a unique complication of a histoplasmoma due to its proximity to the arterial anastomosis in a liver transplant recipient. A key risk factor for histoplasma infection is chronic immunosuppression. Antifungal treatment with itraconazole or amphotericin B is typically used for patients that are symptomatic or immunocompromised. Early recognition and targeted management of histoplasmoma in at-risk populations are critical to preventing severe complications and optimizing outcomes.