When Eosinophils Mislead: Gastrointestinal Basidiobolomycosis Initially Misdiagnosed as Eosinophilic Colitis

Gastrointestinal basidiobolomycosis (GIB) is a rare fungal infection caused by Basidiobolus ranarum that predominantly affects immunocompetent individuals in tropical and subtropical regions. It frequently mimics colonic malignancy or inflammatory bowel disease, leading to significant diagnostic delays.

A 36-year-old previously healthy Indian male presented with a 1-month history of abdominal pain, bleeding per rectum, and weight loss. Computed tomography scan revealed circumferential wall thickening of the ascending colon from the ileocecal junction to the hepatic flexure with loco-regional and para-aortic lymphadenopathy. Colonoscopy demonstrated a large circumferential inflammatory mass causing significant luminal narrowing. Initial histopathology from endoscopic biopsies was interpreted as eosinophilic colitis. However, expert review identified broad, pauciseptate fungal hyphae surrounded by eosinophilic material consistent with the Splendore-Hoeppli phenomenon, confirming GIB. The patient was commenced on oral itraconazole 200 mg twice daily with significant clinical, biochemical, and radiological improvement at 3-month follow-up, without the need for surgical intervention.

This case highlights the diagnostic pitfall of misinterpreting GIB as eosinophilic colitis on superficial endoscopic biopsies and demonstrates successful non-surgical management with itraconazole monotherapy.

GIB should be considered in the differential diagnosis of obstructing colonic masses in immunocompetent patients with eosinophilia. When initial biopsies suggest eosinophilic colitis in the context of a mass lesion, expert histopathological review with attention to fungal elements is essential.

Gastrointestinal basidiobolomycosis (GIB) can closely mimic colonic carcinoma or inflammatory bowel disease endoscopically and radiologically; a high index of suspicion is essential in immunocompetent patients presenting with obstructing colonic masses and peripheral eosinophilia in tropical and subtropical regions.Superficial endoscopic biopsies in GIB frequently yield dense eosinophilic infiltration misdiagnosed as eosinophilic colitis; expert histopathological review focusing on the Splendore-Hoeppli phenomenon on haematoxylin and eosin stain can be diagnostic, and special stains (Grocott-Gomori methenamine silver, periodic acid-Schiff) should be requested when available to further confirm the diagnosis.Early diagnosis of GIB enables curative antifungal therapy and may avert unnecessary surgical resection, underscoring the importance of including this entity in the differential diagnosis of colonic masses with inconclusive initial histopathology.