S4007 Breaking the Mold: A Rare Case of Invasive Colonic Aspergillosis Causing Toxic Megacolon and Perforation in an Immunocompetent Patient

Introduction: Aspergillus is an opportunistic fungus that can affect the gastrointestinal (GI) tract, primarily in immunocompromised individuals. Invasive colonic aspergillosis is exceedingly rare, especially in immunocompetent patients. Previous studies report a 0% incidence in patients without underlying immunosuppression. We present a rare case of colonic aspergillosis causing toxic megacolon and perforation in an immunocompetent young adult. Case Description/Methods: A 24-year-old man with HLA-B27 positivity and intermittent steroid use for joint pain presented with a 1-week history of diarrhea, followed by 4 days of nausea, vomiting, and abdominal pain. Initial labs showed leukocytosis (white blood cell count 19.2 × 10⁹/L), hypokalemia (K 2.5 mmol/L), and elevated creatinine (1.5 mg/dL) with normal liver function tests and lipase. Initial computed tomography imaging revealed significant transverse and sigmoid colonic dilation, consistent with toxic megacolon. Infectious workup was negative. Repeat imaging showed colonic necrosis and perforation, prompting emergent laparotomy with partial colectomy. Histopathology revealed severe colitis with transmural necrosis and fungal elements consistent with Aspergillus. Viral stains for cytomegalovirus, herpes simplex virus, and adenovirus were negative. Despite broad antimicrobial coverage with voriconazole and broad-spectrum antibiotics, the patient remained septic. BAL cultures grew Candida albicans and imaging identified pleural effusions. Antimicrobial therapy was broadened to include amphotericin B and meropenem. Due to persistent hyperbilirubinemia magnetic resonance cholangiopancreatography was obtained showing no biliary obstruction. Extensive hepatic work-up revealed low ceruloplasmin with negative viral hepatitis and HIV. Due to continued fever and colonic inflammation, a colonoscopy was performed with biopsy negative for inflammatory bowel disease. The patient gradually improved over several days and was discharged in stable condition. Discussion: Our patient represents a case of severe fungal colitis with perforation in the absence of traditional risk factors of invasive fungal infections. While he did have remote history of corticosteroid use, it was intermittent and unlikely associated with ongoing immunosuppression. Only one other report describes colonic aspergillosis in an immunocompetent host, who had diabetic ketoacidosis—a known risk factor. This case highlights the need to consider invasive fungal infections in patients with toxic megacolon, even without obvious risk factors.