Acute consumption of C1 inhibitor in a patient with acquired C1-inhibitor deficiency syndrome.

Acquired C1-inhibitor (C1 INH) deficiency is usually found in association with an underlying disease that is believed to be responsible for increased C1 INH catabolism, ultimately leading to the development of C1 INH deficiency. We report a remarkable patient with acquired C1 INH deficiency in whom a unique progression of complement- and contact-system abnormalities has been observed. S. G. suffers from recurrent episodes of angioedema and hypotension. Results of repeated complement studies were initially normal, and the patient was diagnosed as having idiopathic anaphylaxis. Two years later, the patient was found to develop acute consumption of C1 INH with activation of the complement and contact systems during episodes of angioedema. The patient continued to have normal C1 INH levels and to have no evidence for complement- or contact-system activation between attacks of angioedema. One year later, her course evolved into a more typical course for acquired C1 INH deficiency consisting of continuously low functional C1 INH levels with evidence of activation of the complement and contact systems. S. G. provides a unique insight into the development of acquired C1 INH deficiency.