A 16-year-old girl presented to the emergency room with severe swelling of her left hand and forearm. Her symptoms began 12 h earlier with left forearm swelling that progressed to the tips of her fingers. She reported her forearm felt normal, but her hand had a tingling sensation and she was barely able to move her fingers. She also reported having had moderately painful abdominal cramps earlier that day. She denied urticarial or pruritic rashes, respiratory distress, and throat tightness. During the previous week she had felt stressed because of schoolwork and also had developed a mild headache, clear rhinorrhea, and cough. She had never had episodes of swelling in the past.