Heterozygous alpha 1-antichymotrypsin deficiency may be associated with cold urticaria.

Proteins of the serpin family (serine protease inhibitor) control key steps in the inflammatory, coagulation and complement systems. C1-inhibitor deficiency predisposes to hereditary angioneurotic oedema, and other serpins control proteolytic enzymes that may cause complement activation or the forming of oedema. We investigated whether deficiency of proteins of the serpin family may predispose to cold urticaria and therefore screened 7 male patients with severe cold urticaria for the presence of deficiency alleles of some of the members of the serpin antiprotease family. There were no findings of C1-inhibitor, alpha 1-antitrypsin, alpha 2-antiplasmin, antithrombin III, tissue plasminogen activator inhibitor or thyroxine binding protein deficiency. The prevalence of heterozygous alpha 1-antichymotrypsin deficiency was significantly higher than expected (prevalence ratio 25.8 (95% confidence interval 6.0-112), p < 0.0001). This finding is in concert with previous studies that have shown lower mean levels of alpha 1-antichymotrypsin among patients with cold urticaria and suggests that heterozygous deficiency of this antiprotease, which controls neutrophil cathepsin G and mast cell chymase may predispose to cold urticaria. The present series is, however, small and the results need confirmation in larger materials.