HONG KONG (Reuters) - Genes may explain why some people are more susceptible than others to leprosy, an extensive study in China published in the New England Journal of Medicine appears to have found.
The study found mutations of seven genes which appear to increase a person's susceptibility to leprosy, which is in sharp contrast to what experts have believed for a long time - that the disease is not congenital, or inherited.
"All along, people thought it was caused (only) by an infectious agent but our study found it is influenced by genetics. If a parent has the disease, it is highly likely that the child will develop the disease," one of the researchers Zhang Furen at the Shandong Provincial Institute of Dermatology and Venereology in northeast China said by telephone.
"What is interesting is that between couples, if one has the disease, the other remains uninfected for decades ... so how can this (strictly) be an infectious disease? Maybe this disease has to do with inheritability."
"What we found was that apart from the infectious agent, there is an internal reason, we found seven (susceptibility) genes ... it may have a lot to do with genetics (inherited susceptibility)," Zhang told Reuters.
The finding may have similar implications for other germs belonging to the family, like the bug that causes tuberculosis - which killed 1.8 million people last year.
The experts analyzed genes of 706 leprosy patients and 1,225 others without the disease, and mutant versions of the seven genes turned up consistently in those who had the disease. The participants were ethnic Chinese from eastern China.
Five of the genes appear to be involved in regulating the human immune system, said the researchers from China and Singapore.
"Leprosy has a long incubation period of 8 to 10 years, and once the symptoms surface, they would have caused the patient irreversible damage," Zhang said.
"But in future, if we can tell whether a person is susceptible to the disease before symptoms show, we can proceed to take preventive action."
Leprosy, or Hansen's disease, is caused by the Mycobacterium leprae. It affects the skin, mucous membranes, peripheral nerves and eyes. As nerve damage is permanent, even those who have recovered can't feel pain. Minor cuts and abrasions on fingers and toes often turn into gaping, inflamed ulcers because of unsanitary living conditions.
Although leprosy is no longer a problem in advanced countries, this discovery is important because the disease plagues many developing nations.
There were 254,525 new cases of leprosy in 2007 mostly in tropical and sub-tropical countries, according to the World Health Organization.
"In China, there are 2,000 new cases each year," Zhang said.
Reporting by Tan Ee Lyn; Editing by Sanjeev Miglani