Crohn's Disease Developing After Hirschsprung's Disease in a Child With Down Syndrome: A Rare Clinical Overlap.

We describe a rare pediatric case of an eight-year-old boy with Down syndrome who developed Hirschsprung's disease in the neonatal period and was later diagnosed with Crohn's disease, representing an exceptionally uncommon clinical overlap. The patient experienced a complex clinical course marked by necrotizing enterocolitis, intestinal perforation, multiple abdominal surgeries, and persistent gastrointestinal dysfunction from infancy. Despite definitive surgical management of Hirschsprung's disease, he continued to have chronic diarrhea, malabsorption, failure to thrive, and recurrent inflammatory symptoms. Further evaluation revealed markedly elevated fecal calprotectin levels and endoscopic evidence of erosive-ulcerative colitis with pseudopolyps. Radiologic, endoscopic, and histologic findings ultimately confirmed a diagnosis of Crohn's disease with ileocolonic involvement and a recurrent disease course. Initial treatment with corticosteroids and immunomodulators resulted in only partial and transient responses, and therapy was complicated by drug-induced renal impairment. The patient was subsequently escalated to biologic therapy with infliximab, achieving partial control of intestinal inflammation, alongside ongoing nutritional support with a peptide-based enteral formula. This case underscores the diagnostic and therapeutic challenges of inflammatory bowel disease in children with Down syndrome and prior Hirschsprung's disease, in whom postoperative complications and chronic enterocolitis may obscure the diagnosis. It highlights the importance of maintaining a high index of suspicion for Crohn's disease in this population and emphasizes the need for long-term surveillance and a multidisciplinary approach to management in children with complex congenital and inflammatory gastrointestinal disorders.