A 65-Year-Old Man With Abdominal Pain, Duodenal Ulceration, and Skin Lesions

QuestionA 65-year-old man with hypertension presented to the emergency department with one month of persistent abdominal pain and postprandial distress that had not improved despite two hospitalizations at an outside clinic.One month before the current admission, he had developed pain in the right foot along with erythematous skin lesions on the bilateral lower extremities, which had been attributed to cellulitis.Urinalysis revealed elevated white blood cell counts, epithelial cells, and microscopic hematuria.Laboratory workup showed a blood urea nitrogen of 24 mg/dL and creatinine of 0.8 mg/dL.Upper endoscopy demonstrated extensive mucosal hemorrhage and deep ulceration in the duodenum (Fig. 1).CT of the abdomen revealed edematous mural thickening involving the duodenum through the terminal ileum, with multifocal skip lesions most prominent in the duodenum, proximal jejunum, and ileum.Palpable purpura with erythematous to violaceous patches and papules was observed on the bilateral lower extremities.What is the most likely diagnosis?