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Significance of Bronchiectasis in Patients with ₁-Antitrypsin Deficiency

In their article, Dr. Parr and colleagues (1) substantiated the association between ₁-antitrypsin (AAT) deficiency and bronchiectasis, originally described by Guest and Hansell (2). Parr and coworkers noted that a previous study by Cuvelier and coworkers found no association between AAT deficiency and bronchiectasis (3). However, we believe that these two studies (1, 3) are not directly comparable and raise new questions. Parr and coworkers looked for the prevalence of bronchiectasis in a group of individuals with severe AAT deficiency. By contrast, beginning with a group of patients with established bronchiectasis, Cuvelier and coworkers did not identify allelic or phenotypic AAT anomalies as a risk factor. Parr and coworkers noted on CT scan that 95% of their 74 AAT-deficient patients had bronchiectasis involving an average of 3.7 lobes. They further defined "clinically significant bronchiectasis" as bronchiectasis affecting four or more lobes (still a very high prevalence of 77%) and "regular sputum production" (27%), arriving at their prevalence of clinically significant bronchiectasis in AAT-deficient patients of 27%. Thus, the prevalence of CT-diagnosed bronchiectasis affecting 3.7 lobes or more was 77–95%, whereas the prevalence of emphysema was approximately 81%.

The similarity in the frequency of bronchiectasis and emphysema would support the contention by others that bronchiectasis may be secondary to the emphysema (3), also mentioned by Parr and coworkers. Even taking into account different approaches, because diametrically opposing conclusions were reached by Parr and coworkers' and Cuvelier and coworkers' studies, we wonder about the true significance of bronchiectasis in the current study. Utilizing the presence of "regular sputum production" to distinguish clinically significant from nonclinically significant bronchiectasis is not reliable in patients who likely also have chronic obstructive pulmonary disease (COPD) and likely underestimated their report of "clinically significant bronchiectasis."

Since various infections may cause or propagate bronchiectasis, it would also be important to know the microbiologic culture history. In this regard, AAT has antagonistic activity against microbial pathogens (4–6). We recently showed that in 100 patients with primary bronchiectasis due to rapidly growing mycobacteria, the prevalence of AAT anomalies was 27% (6). However, 26 of the 27 AAT anomalies were phenotypically heterozygous (PiMX). Indeed, only 1 of the 27 was homozygous (PiZZ).

Despite our questions, we agree with Parr and coworkers that anomalies in AAT predispose to bronchiectasis. But because they found such a high prevalence of radiographically significant bronchiectasis in their AAT-deficient patients (77–95%), it would be important to perform a case-control study to compare the prevalence of CT-diagnosed bronchiectasis in emphysema patients with and without AAT deficiency.

Edward D. Chan and Michael D. Iseman

National Jewish Medical and Research Center
Denver, Colorado

FOOTNOTES

Conflict of Interest Statement: Neither author has a financial relationship with a commercial entity that has an interest in the subject of this manuscript.

REFERENCES

1. Parr DG, Guest PG, Reynolds JH, Dowson LJ, Stockley RA. Prevalence and impact of bronchiectasis in ₁-antitrypsin deficiency. Am J Respir Crit Care Med 2007;176:1215–1221.[Abstract/Free Full Text]
2. Guest PJ, Hansell DM. High resolution computed tomography (HRCT) in emphysema associated with a₁-antitrypsin deficiency. Clin Radiol 1992;45:260–266.[CrossRef][Medline]
3. Cuvelier A, Muir JF, Hellot MF, Benhamou D, Martin JP, Benichou J, Sesboue R. Distribution of a₁-antitrypsin alleles in patients with bronchiectasis. Chest 2000;117:415–419.[CrossRef][Medline]
4. Shapiro L, Pott GB, Ralston AH. Alpha-1-antitrypsin inhibits human immunodeficiency virus type-1. FASEB J 2001;15:115–122.[Abstract/Free Full Text]
5. Cantin AM, Woods DE. Aerosolized prolastin suppresses bacterial proliferation in a murine model of chronic Pseudomonas aeruginosa lung infection. Am J Respir Crit Care Med 1999;160:1130–1135.[Abstract/Free Full Text]
6. Chan ED, Kaminska AM, Gill W, Chmura K, Feldman NE, Bai X, Floyd CM, Fulton KE, Huitt GA, Strand MJ, et al. Alpha-1-antitrypsin (AAT) anomalies are associated with lung disease due to rapidly growing mycobacteria and AAT inhibits Mycobacterium abscessus infection of macrophages. Scand J Infect Dis 2007;39:690–696.[CrossRef][Medline]

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