Gastrointestinal Klippel-Trénaunay Syndrome Mimicking Ulcerative Colitis: A Case Report.

Introduction: Klippel-Trénaunay syndrome (KTS) is a rare congenital syndrome characterized by the triad of capillary malformation, varicosities, and limb hypertrophy, with an incidence of 2-5 per 100,000. Gastrointestinal (GI) involvement in KTS may be present in over 30% of patients, typically presenting with pain and bleeding. While bleeding is a well-described symptom of GI involvement in KTS in the medical literature, diarrhea remains an uncommon and underreported manifestation. This report highlights this unique finding and the diagnostic complexity it presents. Case Presentation: A 64-year-old male presented to the hospital with recurrent foul-smelling bloody diarrhea over the past two months. He had been previously diagnosed and treated for ulcerative colitis. Physical examination revealed pallor, macrodactyly, and segmental hypertrophy of the lower left limb. Investigations demonstrated severe iron-deficiency anemia, splenomegaly, fundal varices, and a continuous 15-cm colonic involvement from the anal verge with varicosities and bleeding. This led to the establishment of a diagnosis of KTS. Conclusion: This case highlights the diagnostic challenge that may arise from the complexity and variability of KTS presentations, which can mimic inflammatory bowel disease (IBD) due to findings like bloody diarrhea and extensive colonic involvement. Although diarrhea is rarely reported as a manifestation of KTS, it might result from existing GI vascular and lymphatic malformation, potentially leading to protein-losing enteropathy. Awareness of this atypical presentation and early multidisciplinary evaluation are crucial for symptom control, preventing complications, and improving quality of life.