A 14-year-old girl presented with diarrhea and bloody stools was initially diagnosed with infectious colitis and anal fissure. The patient was treated with antibiotics
however, the symptoms persisted and purpura appeared on the patient's lower abdomen. Abdominal computed tomography indicated diffuse wall thickening of the entire colon. A colonoscopy revealed extensive edema, several ulcers, and mucosal friability, resulting in the diagnosis of ulcerative colitis. Blood tests revealed hypoalbuminemia, increased inflammatory marker levels, and high proteinase3 anti-neutrophil cytoplasmic antibody (PR3-ANCA) levels. Urinalysis showed hematuria and casts, raising the suspicion of concurrent vasculitis syndrome. Esophagogastroduodenoscopy revealed multiple punched-out ulcers in the esophagus. Granulomatosis with polyangiitis with gastrointestinal involvement was diagnosed combined with the positive PR3-ANCA results and skin and renal involvement. Steroid therapy was initiated, leading to the rapid improvement of diarrhea, purpura, and esophageal ulcers. While high PR3-ANCA levels are occasionally observed in ulcerative colitis, esophageal ulcers in patients with granulomatosis with polyangiitis often result in poor symptoms. Thus, esophagogastroduodenoscopy should be considered in patients with high PR3-ANCA levels, even in the absence of upper gastrointestinal symptoms.