Asthma is not a genetic disease, according to a new study. Commonly found genetic mutations account for only a small part of the risk of acquiring the disease, a study by scientists at the University of Chicago has shown. Mutations occurring have been thought to explain the occurrence of a genetic disease when it is not hereditary, but in a genome study of about 11,000 individuals, the study found mutations in just three genes associated with asthma.

The study, published in Nature Communications, suggests that previous studies overestimated the heritability of asthma. Since people of the same family share the same environment, diseases that are caused by the environment may seem to be genetic.

Asthma affects more than 25 million people in the United States. In the new study, led by Carole Ober, PhD, Blum-Riese professor and chair of the Department of Human Genetics at the University of Chicago, evaluated nearly 33,000 rare or low frequency mutations in 11,000 people across ethnicities using a technique that allowed the researchers to study mutations common in one ethnicity and rare in others.

Mutations in the GRASP, GSDMB and MTHFR genes were found to be statistically associated with asthma risk. Mutations in the first two genes were found primarily in Latino individuals, and mutations in the last gene in individuals of African ancestry. These mutations were found in just 5 per cent of the population. The rarity and ethnic specificity of these mutations mean they cannot account for asthma, which is widespread across ethnicities.

The GRASP, GSDMB and MTHFR genes are involved in protein-building, regulating cell death and metabolising vitamin B9. Although they do not account for asthma risk, these genes could serve as therapeutic targets. This process has been used before in the discovery of a treatment for high cholesterol.

Asthma kills nine people every day in the United States.

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