LONDON (Reuters) - Scientists have found a link between genetic variants in an area of the genome that controls immune response and the risk of contracting podoconiosis, a disfiguring and disabling leg disease that affects almost 4 million people, mainly in Africa.
In a study published in the New England Journal of Medicine on Wednesday, researchers compared the genomes of 194 people in southern Ethiopia affected by the disease with 203 people in the same region who were not affected. They found three genetic variants that increase the risk of developing the disease.
Podoconiosis, or “podo” as it is often called, is a type of elephantiasis, or leg swelling, caused by an abnormal reaction to minerals found in soil.
It is found in farming communities in tropical Africa, Central America and northwest India, often among people who cannot afford shoes. It was added to a World Health Organisation (WHO) list of neglected tropical diseases in 2011.
“There are still many places round the world where people cannot afford a pair of shoes,” said Gail Davey, a co-researcher on the study. “For some people, this means cold, cut or bruised feet, but for others it can lead to podoconiosis, which can have a significant impact on their quality of life”.
Experts say years of walking, ploughing or playing barefoot on soils of volcanic origins which contain irritant mineral particles appears to trigger changes in the lymph system in the legs, which in time can lead to swelling in the feet and legs.
According to the Geneva-based WHO, around a million people in Ethiopia and another 500,000 in Cameroon are estimated to be affected by podoconiosis.
The economic consequences are severe, the WHO says, with productivity losses amounting to 45 percent of working days per year for each patient - suggesting economic losses to a country like Ethiopia of more than $200 million per year.
The disease often runs in families, implying there is likely to be a genetic component to it, but until now no genetic variants had been linked to it.
Melanie Newport from Britain’s Brighton & Sussex Medical School, who led the study, said the three variants she and her team found were all in a region of the genome that plays an important role in controlling the immune system.
“Although this is still early days for identifying potential treatments, it suggests that drugs that target immune responses may be useful,” she said in a statement about the findings.
Fasil Tekola Ayele of the Armauer Hansen Research Institute in Ethiopia, who also worked on the team, said that this sort of genetic study is still fairly uncommon in African populations but the results of the latest one highlight their importance.
The research team said the next step would be to try to pinpoint exactly which molecules are involved in podoconiosis, and which specific genetic mutations affect the function of those molecules.
“This will shed a lot more light on potential therapeutic options,” said Abraham Aseffa, also from the Armauer Hansen Research Institute.
Editing by Hugh Lawson