Prather Pediatric and Allergy Center - Ask Doctor Brent

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Title: Is There a Single Gene for Asthma?

Category: Asthma and Allergy



Since Dr. Vander Veer studied the heredity of asthma and hay fever in 1916, we have wondered just how allergies are inherited. There is no doubt that heredity is a big factor. We know that children of allergic parents are much more likely to have allergies including asthma and to develop them at a younger age. However, we still, to this day, do not know exactly how asthma or allergies are inherited. In the last few years, studies seem to isolate a specific marker on chromosome 11 which codes for asthma. These studies are fascinating but have not been totally accepted by genetic experts and further studies will have to clarify their significance.

One of the best ways of studying the inheritance of allergies or anything else is to study twins. Most twin studies show a much higher likelihood of having similar allergies if the twins are identical as opposed to being fraternal twins. I did a twin study in the late seventies at Tulane and LSU involving about 60 sets of twins. My findings showed a much higher concordance in identical twins for all types of allergies such as hay fever, asthma and eczema. Interestingly, the exact match of either asthma, hay fever or eczema did not occur but the general tendency to have one of these allergies was higher among identical twins than fraternal. I read the results of thousands of studies preceding mine and hundreds since mine and they all add bits of information to the puzzle. No single study, however, gives us a specific answer as to a defect on any given gene or chromosome causing all the allergy problems.

Besides genetic tendencies which are probably found somewhere in our chromosomes, inherited from our parents and affected by our family trees, another factor which is of critical importance in developing asthma and allergies include environmental exposure. In other words, is there cigarette smoke in the home, particularly during a child's infancy? If so, that child is more likely to have respiratory problems including asthma. Does the home have a high quantity of house dust mite? If so, studies show a greater chance of developing both hay fever and asthma and at a younger age. Was the child born premature? If so, there is a greater likelihood of the child developing respiratory problems including asthma. Other factors include air pollution, the time of day that the child is exposed to certain environmental allergens and irritants, the sex of the child, what infections they encounter particularly in the early months of life, and what medications children are given. All of these other factors which contribute to the development of asthma and allergies greatly complicate the original question, "Is there an asthma gene?" The answer is still unknown, but keep watching; we may have a definitive answer very soon.