Genetic cause of 'spongy hands' discovered 4 July 2013 Last updated at 06:27 By Helen Briggs BBC News Scientists have mapped the gene behind a rare skin condition where hands turn white and spongy in water. Studies of British and Swedish families with the condition revealed a genetic change in a key chemical that controls water loss from the body. About one in 40,000 people have the disease, which causes thickened skin on the palms and soles. Researchers in London say the discovery will aid understanding of how the skin moisturises itself. The genetic study gives an insight into how the skin barrier functions, said David Kelsell, professor of human molecular genetics at Queen Mary, University of London, who led the team. He said the research, published in The American Journal of Human Genetics, could also help investigations into other skin conditions. "This may help us understand more about how the skin moisturises itself naturally," Prof Kelsell told BBC News. Everyone knows that when you sit in the bath for an hour your skin goes white and wrinkly. This is what happens in people [with the skin condition]- but it just happens a bit quicker. The condition is called diffuse non-epidermolytic palmoplantar keratoderma. The underlying cause is a fault in a substance called aquaporin 5, which plays a role in the generation of saliva, tears and other secretions. The research shows it is also present in the skin, with higher amounts in the hands and feet. The gene change appears to make the skin more porous, allowing water to permeate the skin more rapidly.