Acquired C1-esterase inhibitor deficiency: a rare cause of episodic acute abdominal pain and ascites.

C1-esterase inhibitor deficiency is a rare yet classic medical cause of acute abdominal pain mimicking a surgical emergency. A hereditary form and a very rare acquired form of the disease exist, and both give rise to a similar clinical syndrome despite a different pathogenic mechanism. We describe a typical case of acquired C1-esterase inhibitor deficiency in a 65-year-old woman presenting with recurrent acute abdomen and ascites who had undergone two negative surgical interventions before diagnosis was eventually established. Both the diagnostic and therapeutic approach to this rare condition should be known by emergency physicians for two reasons: (1) it may present as an acute abdominal emergency resulting in unnecessary surgical intervention; and (2) it may cause life-threatening upper airway obstruction as a result of laryngeal oedema.