Researchers are unlocking the causes of a painful condition that swells the arms and legs of sufferers.
Genes connected with lymphoedema have emerged
Thousands in the UK suffer from lymphoedema, which happens when excess fluid cannot be drained from the body's extremities.
Some cases are thought to be inherited and Finnish scientists have found a body chemical which appears to play a key role.
The discovery could eventually help produce effective treatments.
The lymph system runs parallel to the bloodstream, and one of its jobs is to transport excess fluid from the body's tissues back into the blood.
When this process fails, there is fluid buildup in the arms and legs, which can be extremely uncomfortable for sufferers.
At present there are only limited measures to reduce the problem once it has developed, and while some cases have an obvious cause - such as cancer surgery in the armpit which disrupts the lymphatic vessels, scientists are still unsure in many cases what exactly is going wrong.
Researchers from the University of Helsinki have been working to identify the chemical processes which operate the lymphatic drainage system.
There is hope that if some cases are due to malfunctioning genes, they might be able to partially or even wholly correct the problem in some patients.
The Finnish team have focused their attentions on a chemical called vascular endothelial growth factor C (VEGF-C).
Experiments in mice suggest that those bred lacking one or both copies of the correct gene in their DNA are severely affected by lymphatic drainage problems.
Those completely missing the correct gene die before birth, their organs distorted by excess fluid.
Those with only one good copy develop swollen paws.
They also have problems with the movement of immune cells throughout the body - another key function of the lymphatic system.
Combination of genes
Dr Kari Alitalo, who led the research, said that mutations in the gene for VEGF-C, might be responsible for some inherited cases of lymphoedema.
The mice created for the experiment could provide a valuable animal model of the disease which would help produce new therapies.
Glen Brice, a researcher in the genetics of lymphoedema at St George's Hospital Medical School in south London, said that research there had identified a related gene as having a role in some forms of the condition.
However, he said that it was likely that a combination of faulty genes was at work in many inherited cases, rather than just one.
"We have made significant progress against lymphoedema in the past five or six years - when we found the location of this first gene," he said.