Scientists have pinpointed a gene which has been found to be a major cause of asthma in a significant proportion of cases.

The condition is caused by an allergic reaction leading to inflammation of the tissues of the lungs.

Our research could lead to entirely new ways of diagnosing and treating asthma

Professor Stephen Holgate

This in turn causes the airways to contract too readily, leading to coughing, wheezing and breathlessness.

The new discovery could lead to new treatments to prevent asthma from developing even if there are signs of an allergic reaction in the lungs.

At present the only way to treat the condition is to use drugs to suppress the inflammation or to dilate the constricted airways.

It could also allow childhood screening for asthma, so those found to be at risk could get earlier treatment.

Scientists from the Medical Research Council in the UK, and the Schering Plough Research Institute in the US carried out a comprehensive analysis of the genes of 460 pairs of brothers and sisters.

New treatments

They found that the way the lungs respond to the stimulants that can cause asthma seemed to be controlled by an area of genetic material found on chromosome 20.

Further analysis revealed that a gene in this area called ADAM33 plays a crucial role in making the airways of the lungs over-sensitive, thus increasing the risk of asthma.

The discovery will help us to understand why asthma might develop in the first place

Donna Covey

The scientists estimate that the gene could play a significant role in 40% of all cases of asthma.

MRC Professor Stephen Holgate, of Southampton University, who led the research said it was the first time that a comprehensive analysis had identified a gene as being a key component of asthma.

He said: "We're very excited about this discovery.

"Our research could lead to entirely new ways of diagnosing and treating asthma.

"This holds great promise for benefiting the huge numbers of people who suffer from this condition, one of the most prevalent chronic illnesses in children today."

Donna Covey, Chief Executive, UK National Asthma Campaign said the study was a "very excitng step forard in unravelling the genetics of asthma."

She said: "The discovery will help us to understand why asthma might develop in the first place and its findings will enable the scientific community to push forward with further research.

"This discovery leads onto further questions such as how asthma genes interact with environmental and lifestyle factors. It could potentially enable better and earlier targeting of treatment for people with asthma."

Common condition

Asthma affects one in five children and one in ten adults in the UK.

An estimated eight million people in the UK have been diagnosed with asthma at some stage in their lives and the disease worldwide is increasing.

The condition is thought to be linked to factors such as cold air and exercise as well as exposure to substances that provoke the allergic reaction such as house dust mites, animal fur, pollens and fungi.

Air pollution including passive smoking, virus infections and changes in diet have also been linked to the condition.

The research is published in an online edition of the journal Nature.