Scientists have discovered a gene fault which makes people more likely to develop leprosy.
Leprosy patients in East Delhi, India, waiting for treatment
Although many perceive it as a "biblical disease", leprosy still affects up to a million people a year.
Experts from McGill University in Montreal, Canada, found the genetic variation means a person has five times the normal risk of developing leprosy.
Writing in the journal Nature, they say the finding will help develop ways to prevent and treat the disease.
Leprosy is a chronic disease caused by the bacteria Mycobacterium leprae, which is passed on through direct personal contact or contaminated respiratory droplets.
Symptoms include pigmented skin lesions, permanent nerve damage leading to numbness of the feet and hands.
If it is left untreated, people can lose fingers, toes, feet or hands to the disease.
The researchers from McGill, along with scientists from France's National Institute for Health and Medical Research, analysed DNA samples from almost 200 Vietnamese families who had a history of leprosy.
The human cell nucleus contains 23 pairs of chromosomes, which carry genetic information necessary for developing and running the body correctly.
The McGill researchers found the families shared a variation of the Parkin gene and a neighbouring gene called PACRG which are both found on chromosome 6.
The results were confirmed by DNA testing of 1,000 people in Brazil.
Both genes have also been linked to Parkinson's disease.
Dr Erwin Schurr, who led the leprosy research, said: "This discovery will now allow us to study how the gene works and how it influences the infectious process.
"This is an important step toward the development of innovative prevention and treatment strategies for leprosy", stated Dr Schurr.
Dr Marcel Behr, an infectious disease specialist at McGill, added: "Leprosy has plagued humans for many centuries and it continues to be a concern in many countries.
"These studies lead the way to developing better treatment and a possible vaccine."