Acquired C1 esterase inhibitor deficiency

Acquired C1 esterase inhibitor deficiency is a rare condition associated wi th autoimmune or low-grade lymphoproliferative disorders. Adults or elderly patients are most commonly affected. The diagnosis is suspected when patie nts present with recurrent angioedema and low serum levels of C4 with norma l levels of C3. Low levels of Clq and low C1 esterase inhibitor activity co nfirm the diagnosis. In this paper, we summarize experience with 22 cases of acquired C1 esteras e inhibitor deficiency in the context of a review of the published literatu re on diagnosis and treatment of this condition.