Asthma and heterozygous α1‐antichymotrypsin deficiency: a possible association

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Abstract
During studies of families with .alpha.1-antichymotrypsin deficiency heterozygotes, an apparently increased prevalence of asthma among first degree relatives was noticed. In a case control study, the prevalence of asthma among first degree relatives of 12 women with heterozygous .alpha.1-antichymotrypsin deficiency was compared with that of first degree relatives of 58 matched controls. Secondly, the strength of association between asthma and low or subnormal plasma ACT concentration, in first and second degree relatives to heterozygotes, was assessed. The prevalence of asthma among first degree relatives of women with heterozygous .alpha.1-antichymotrypsin deficiency was significantly higher [prevalence ratio 3.22 (1.06-9.83), P = 0.04]. Among heterozygotes, the prevalence of asthma in first and second degree relatives with low plasma .alpha.1-antichymotrypsin concentration was higher than in relatives with normal plasma ACT concentration, but the difference in prevalence did not reach statistical significance [prevalence ratio 3.1 (0.96-9.83), P = 0.059]. The findings are in agreement with previous studies and suggest a possible association between asthma and heterozygous .alpha.1-antichymotrypsin deficiency.