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 polymorphism 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 increased
risk of developing a chronic cough.
methods: We recruited 47 patients (33 women), referred for
evaluation 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 challenge. ACE genotyping was performed on DNA samples from
patients using the polymerase chain reaction followed by agarose gel
electrophoresis. ACE genotypes in patients with chronic cough were
compared with those in 199 healthy control subjects. Serum ACE levels
were determined using a colorimetric assay.
Genotype frequencies for the ACE gene were similar between patients and
control subjects. There was no correlation between capsaicin
sensitivity and ACE genotypes or serum ACE levels.
Conclusion: Susceptibility to develop chronic cough is not
associated with ACE genotype.