Angioedema due to acquired C1-esterase inhibitor deficiency in a patient with Helicobacter pylori infection.

The first component of the classical pathway of the complement system, C1 is regulated by a serum protein, the C1-esterase inhibitor (C1-INH). Deficiency of this protein leads to the release of vasoactive mediators (C2 kinin and bradykinin) that increase vascular permeability and can induce edema formation in subcutaneous and submucosal tissues. The genetic variant of C1-INH deficiency is inherited as an autosomal dominant trait and causes hereditary angioneurotic edema. The acquired form of C1-INH deficiency is characterized by similar manifestations and can occur in association with lymphoproliferative diseases, malignancy, immune disorders, and infections. The authors present a case of acquired C1-INH deficiency in a patient with Helicobacter pylori infection. Complete eradication of this pathogen was followed by the resolution of symptoms and normalization of serum complement levels. It seems therefore probable that in this patient, acquired C1-INH deficiency was related to Helicobacter pylori infection. To our best knowledge, no similar observations have been published so far. Specific immune reactions are important contributing factors in H. pylori. Excessive consumption of complement by antibodies directed against H. pylori is a potential cause of C1-INH deficiency observed in our case.