Z and S mutations of the alpha1-antitrypsin gene and the risk of chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) has been associated with heterozygosity for the Z and S alleles of the alpha1-antitrypsin gene in some studies, but these observations have not been confirmed by others. Cigarette smoking is the major risk factor for COPD and may have been a confounding factor in many of the previous studies. We investigated whether the Z or S alleles were more prevalent in a group of heavy smokers with COPD than in a group of nonobstructed smokers. Forced expiratory volume in 1 s and forced vital capacity were derived for 266 patients undergoing lobar or lung resection. These lung-function measurements were used to divide the patients into a COPD group and a group of nonobstructed control subjects. The subjects were typed for the Z and S alleles of the alpha1-antitrypsin gene using a polymerase chain reaction-based technique. In the COPD patients, 12 of 193 (6%) were heterozygous for the Z allele (MZ) compared with 0 of 73 control subjects, which gave a P value of 0.04 after correction for age, gender, and smoking history. There was no association of the S allele with COPD. The results indicate that the Z, but not the S, allele is a risk factor for COPD in the heterozygous state.