Vascular Malformation in the Gastrointestinal Tract Mimicking Vasculitis: A Case Report.

Diagnosing vasculitis is challenging because it lacks pathognomonic signs and symptoms. Gastrointestinal vasculitis further complicates the picture, given its high mortality risk and the potential absence of systemic manifestations; thus, a systematic approach that includes ruling out vasculitis mimickers is useful. We report the case of a 29-year-old male evaluated for suspected intestinal vasculitis due to recurrent rectal bleeding, weight loss, fatigue, elevated inflammatory markers, high immunoglobulin E (IgE) levels, and positive anti-neutrophil cytoplasmic antibodies (ANCA), coupled with computed tomography (CT) showing diffuse parietal thickening of the anus, rectum, and sigmoid colon. These findings raised suspicion for eosinophilic granulomatosis with polyangiitis, prompting high-dose corticosteroid therapy before definitive diagnosis. However, contrast-enhanced magnetic resonance imaging (MRI) later revealed phleboliths and venous lakes, indicating gastrointestinal diffuse cavernous hemangioma (GDCH). Sirolimus was introduced to facilitate steroid tapering and to reduce bleeding, ultimately leading to significant lesion regression and symptom resolution. This case underscores the importance of excluding vasculitis mimickers - particularly vascular malformations - when evaluating potential gastrointestinal vasculitis.