A case of angioedema due to acquired C1 esterase inhibitor deficiency masquerading as suspected peritonitis: a case report.

Angioedema due to acquired C1 esterase deficiency is a rare condition and a non-inflammatory disease characterized by episodes of edema of the mucosa of the upper airway or gastrointestinal tract. The purpose of this case report is to heighten awareness among emergency physicians of a peritonitis-like condition that can develop into angioedema due to acquired C1 esterase inhibitor deficiency, and thereby help to prevent false diagnosis resulting in unnecessary surgical intervention. We report the case of a 21-year-old man who presented to the Emergency Department (ED) with abdominal pain. He was later diagnosed with angioedema of the gastrointestinal tract due to acquired C1 esterase deficiency that was initially suspected as peritonitis. Careful evaluation of the acute abdomen in acquired C1 esterase deficiency is very important in the ED to distinguish between medical and surgical causes of an acute abdomen.