A drug used to treat rheumatoid arthritis could help asthma patients, scientists said on Friday, as they identified two mutant genes that may predispose a person to asthma. Over 235 million people worldwide suffer from asthma and it is the most common chronic disease among children, according to the World Health Organization. In a paper published in The Lancet medical journal, researchers in Australia said they had identified the two rogue genes after comparing 58,000 DNA samples of people living in Australia, Europe and the United States with and without asthma.