Is there an association between angiotensin-converting enzyme gene variants and chronic nonproductive cough?

Background: It is unclear why some patients develop a chronic nonproductive cough, Angiotensin-converting enzyme (ACE) inactivates tussive peptides in the airways such as bradykinin and tachykinins, An insertion/deletion poly morphism in the ACE gene accounts for variation in ACE levels, and patients with the II genotype have lowest serum ACE levels compared with ID and DD genotypes. We hypothesized that the II genotype would be associated with in creased risk of developing a chronic cough. Materials and methods: We recruited 47 patients (33 women), referred for ev aluation of cough (median cough duration, 24 months; range, 2 to 240 months ). Cough patients were evaluated using a comprehensive diagnostic protocol, and cough reflex sensitivity was measured using a capsaicin inhalation cha llenge. ACE genotyping was performed on DNA samples from patients using the polymerase chain reaction followed by agarose gel electrophoresis, ACE gen otypes in patients with chronic cough were compared with those in 199 healt hy control subjects. Serum ACE levels were determined using a colorimetric assay. Results: Genotype frequencies for the ACE gene were similar between patient s and control subjects, There was no correlation between capsaicin sensitiv ity and ACE genotypes or serum ACE levels, Conclusion: Susceptibility to develop chronic cough is not associated with ACE genotype.