Eosinophilic Colitis and Crohn’s Disease: A Rare Overlapping Entity in an Adult

Background: Eosinophilic colitis (EC) is a rare form of primary eosinophilic gastrointestinal disorder, predominantly affecting neonates and young adults. Unlike eosinophilic esophagitis, EC remains poorly understood, with limited data derived from small case series and reports. It is characterized by eosinophilic infiltration of the intestinal wall, submucosal edema, and peripheral eosinophilia. However, the presence of eosinophils in colonic biopsies necessitates ruling out secondary causes, making EC a diagnosis of exclusion. Case Presentation: We report the case of a 32-year-old male with no significant medical history who presented with recurrent watery diarrhea over seven months, associated with atypical diffuse abdominal pain, predominantly in the right iliac fossa. Laboratory findings revealed an inflammatory syndrome, mild peripheral eosinophilia, and positive ASCA antibodies, while biochemical tests were unremarkable. An abdominal CT scan showed thickening of the right colon and cecum with adjacent infiltration. Colonoscopy revealed erythematous cecal mucosa with superficial ulcerations, along with edematous and erythematous mucosa in parts of the right colon. Histopathological analysis of colonic biopsies demonstrated overlapping features of eosinophilic colitis and Crohn’s colitis. The patient was treated with corticosteroids and azathioprine (2.5 mg/kg/day), leading to significant clinical and biological improvement. Discussion: A review of the literature reveals considerable variability in the role of eosinophils in both inflammatory bowel disease and eosinophilic colitis. While eosinophilic infiltration is commonly observed in IBD, its exact significance remains unclear. The coexistence of EC and Crohn’s disease is rare and raises questions regarding a possible shared immunopathological mechanism. Conclusion: This case underscores the importance of considering eosinophilic colitis in the differential diagnosis of chronic diarrhea with eosinophilia, pa