Gastrointestinal bleeding with joint pain

A 22-year-old male presented with fever, diffuse abdominal pain and melena for 2 days. He also had symmetric polyarthralgia involving knee and ankle. Physical examination showed no peripheral lymphadenopathy or joint swellings. Investigations showed normal blood count, kidney function tests with raised serum transaminases, AST 76 U/L and ALT 82 U/L (normal <40U/L). Urinalysis revealed no hematuria or proteinuria. Computed tomography (CT) abdomen showed diffuse thickening of small bowel (Figure 1A). Esophagogastroduodenoscopy showed hyperemic edematous mucosa with ulcerations in the duodenum (Figure 1B). After two days patient developed multiple reddish purpura over bilateral lower limbs (Figure 2). What is the possible diagnosis?