WASHINGTON, July 6 (Reuters) - European researchers said on Sunday they had identified a new gene that, when mutated, almost doubles the risk of developing a paralyzing disease.

People with the mutations had 1.8 times the risk of developing amyotrophic lateral sclerosis, also known as motor neuron disease or Lou Gehrig's disease, they found.

Peter Carmeliet of the Flanders Interuniversity Institute for Biotechnology in Leuven, Belgium, and colleagues also found that mice bred with a similar mutation were unusually prone to paralytic disease.

The gene they looked at, VEGF, had not previously been associated with ALS, which affects between 1 and 2 in every 100,000 people around the world.

ALS usually develops after age 50, causing gradual weakness, then paralysis and death. There is no cure, although some people progress more quickly than others.

Carmeliet's team had found that mice with a defective version of VEGF, which caused their bodies to produce less VEGF protein than normal, developed a disorder similar to ALS.

They looked at samples from 1,900 people from Sweden, Belgium and Britain and found those with certain mutations of VEGF produced low levels of the protein, too -- and had a 1.8 times higher risk of ALS than the general population.

Furthermore, when they gave VEGF to mice with artificially induced ALS symptoms, the mice got better, they reported in the journal Nature Genetics.

The findings suggest that VEGF plays a role in ALS, they wrote. "The findings also raise the intriguing question whether more long-term treatment with VEGF might delay the onset or slow the progression of adult-onset motoneuron degeneration as well," they wrote.

VEGF, short for vascular endothelial growth factor, is known to play an important role in blood vessel growth and development, so the finding may also shed light on the underlying causes of ALS.