Question: A 48-year-old man was referred to our hospital with a 12-hour history of acute massive upper gastrointestinal (GI) bleeding. He denied previous similar episodes or chronic medical illnesses. Two days before admission, he was seen in another hospital for acute febrile illness, for which he was given an empirical antibiotic in a form of clavulanted amoxicillin and oral paracetamol, and his fever subsided. On the day of admission, he developed severe hematemesis and hematochezia, but no bleeding from other sites. On arrival to our hospital, he was very pale, afebrile, and hemodynamically unstable with a pulse rate of 120 beats/min and a blood pressure of 80/50 mm Hg. He exhibited no peripheral stigmata of chronic liver disease, and the abdominal examination disclosed no organomegaly or ascites. The liver span was within normal limits. Physical examination of other systems was unremarkable. His initial laboratory tests revealed low hemoglobin (6 g/dL), a platelet count of 50,000/cm 3 leucopenia, high prothrombin time and partial thromboplastin time, normal D-dimer, normal renal function tests and normal liver function tests, except for hypoalbuminemia. Ultrasound examination of the abdomen showed normal liver texture and no features suggestive of portal hypertension. After intensive resuscitation (with intravenous fluids, blood, fresh frozen plasma, and platelet transfusion) urgent upper GI endoscopy was done (Figure A, B). The next day, again he developed severe upper GI bleeding and lapsed into hypovolemic shock. He was resuscitated and underwent repeat upper GI endoscopy, which showed the same findings. On the same, day his platelet count decreased to 35,000/cm 3. Blood culture was negative for gram-positive organisms, gram-negative organisms, and anaerobes. He was given platelet and fresh frozen plasma transfusions. His condition gradually improved. A few days later, he was discharged in good condition with normal complete blood counts. What is the most likely diagnosis? See the Gastroenterology web site (www.gastrojournal.org) for more information on submitting your favorite image to Clinical Challenges and Images in GI.