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You are seeing a 7 year old patient with his third lifetime episode of angioedema. He has swelling around both eyes and his right upper lip, but none of his tongue or pharynx, and he is maintaining his airway. He has a history of multiple food allergies. Besides lack of urticaria or itching, which of the following findings supports hereditary bradykinin-mediated angioedema over allergic histamine-mediated angioedema as the underlying pathophysiology?