Atypical bronchial tubes: a risk factor for lung disease

There is now strong evidence that chronic obstructive pulmonary disease (COPD) is not only a danger of smoking. Indeed, the way in which a patient’s bronchial tubes are configured can increase his or her risk of suffering from COPD, whether or not the individual is a smoker. This discovery, to which Benjamin Smith, researcher at the McGill University Health Centre, contributed, led to the identification of a marker to recognize patients who are at a higher risk for COPD, even before the earliest symptoms appear.

One-quarter of patients who suffer from COPD (emphysema or chronic bronchitis) are non-smokers.

COPD is the fourth leading cause of death in North America. In the past several years, the number of cases (90% of which are linked to smoking) has been on the rise despite the fact that there are fewer and fewer smokers. Recent studies have shown that one-quarter of patients who suffer from COPD (emphysema or chronic bronchitis) are non-smokers. And not all smokers develop this debilitating lung condition. While variations in the genes involved in bronchi development have been associated with COPD, the missing link remained.

Smith and a team of American researchers used computerized axial tomography—an x-ray medical imaging technology—to get a closer look at patients’ bronchial tree. Much like a set of different sized tubes, the bronchi and bronchiole help air and oxygen enter the lungs. Conventional medical wisdom believed that all human bronchi are configured in the same way, so it’s no wonder that the researchers were surprised to find that 26% of the 3 000 bronchial trees that were scanned were atypical, with more or fewer bronchi. Smith likens this malformation, which is hereditary, to having four or six fingers! When they linked the number of bronchi to the cases of COPD, the researchers noted that an extra bronchial tube increases a patient’s COPD risk factor by 40%. People missing a bronchi have a 50% higher risk but only if they smoke.

Benjamin Smith is currently following cohorts of smokers over time to see whether atypical bronchi have a negative impact on the progression of the disease. If they do, the findings will certainly reinforce the importance of butting out to breathe better!