Chest
Volume 117, Issue 2, February 2000, Pages 415-419
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Clinical Investigations
Distribution of α1-Antitrypsin Alleles in Patients With Bronchiectasis

https://doi.org/10.1378/chest.117.2.415Get rights and content

Study objectives

Bronchiectasis has been reported in a few patients with homozygous α1-antitrypsin (AAT) deficiency, but the distribution of AAT alleles among bronchiectatic patients is not known.

Patients and design

Two hundred two patients, 104 men and 98 women, with a mean age (SD) of 63.7 ± 15.4 years, had bronchiectasis diagnosed by CT scan alone (n = 178), bronchography with or without CT scan (n = 17), or radiography alone (n = 7). AAT phenotypes (classified according to the protease inhibitor [PI] system) were determined by isoelectric focusing in blood samples obtained from all patients. Bronchiectasis was primary in 121 cases and secondary in 81 patients. Allele and phenotype frequencies were compared retrospectively between bronchiectatic patients and healthy blood donors living in the same geographic area.

Results

The PI phenotype frequencies among patients were the following: MM, 81.18%; MS, 11.88%; MZ, 3.46%; IZ, 0.49%; IM, 0.49%; SS, 1.48%; SZ, 0.49%; and ZZ, 0.49%. The allelic frequencies among patients were the following: M, 89.1%; S, 7.67%; Z, 2.72%; and I, 0.49%. There was no difference in the distribution of alleles or phenotypes either between patients and control subjects or between patients with secondary and primary bronchiectasis. A significant difference was found between bronchiectatic patients with and without coexisting emphysema (p = 0.028). This difference was caused by an overrepresentation of PI*Z alleles in bronchiectatic patients with coexisting emphysema.

Conclusions

Our results do not support a physiopathologic implication of the AAT genes in the development of bronchiectasis. We suggest that bronchiectasis may be a consequence of emphysema in PI*Z patients rather than a primary effect.

Section snippets

Patients and Control Population

We retrospectively studied all the clinical files in our department between January 1991 and June 1996. Two hundred forty patients were classified as having bronchiectasis according to the World Health Organization International Classification of Diseases.9 All these subjects were hospitalized or were seen at the outpatient clinic of our department. AAT phenotype analysis was already available for a few patients or was retrospectively determined in as many patients as possible. Twenty-five

Patients' Data

The study population involved 202 patients (104 men and 98 women) with a mean age (SD) of 63.7 ± 15.4 years (range, 17 to 90 years). One hundred ninety-seven patients (97.5%) were white, 4 were African (2.0%), and one was Asian (0.5%). One hundred thirteen patients were nonsmokers (55.9%), 58 were ex-smokers (28.7%), and 31 were active smokers (15.3%). Diagnosis of bronchiectasis was assessed by CT scan alone in 178 patients, CT scan and bronchography in 16 patients, bronchography alone in 1

Discussion

Our study indicates that AAT phenotype distribution and gene frequencies are not different between patients with bronchiectasis and control subjects. We observed the presence of one PI*Z homozygous and two PI*I heterozygous individuals in the subgroup of bronchiectatic patients with emphysema. Although our observation regarding the Z allele is not surprising, inasmuch as this allele is associated with an increased incidence of emphysema, it is more surprising regarding the I allele, the

Acknowledgments

The authors thank Luis Carlos Molano and Richard Medeiros for their advice in editing the manuscript.

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