Genetic cause of 'spongy hands' identified

Scientists have identified the genetic cause of a rare skin condition that causes the hands and feet to turn white and spongy when exposed to water.
Diffuse non-epidermolytic palmoplantar keratoderma (NEPPK) is a rare condition in which individuals have thickened, yellowish skin over their palms and soles, thickened nails and suffer from excessive sweating.
When their hands and feet are exposed to water, the skin quickly turns white and spongy and individuals are prone to fungal infections.
A team led by David Kelsell, Professor of Human Molecular Genetics at from Queen Mary, University of London, studied DNA from a number of families of British and Swedish origin in which the skin condition is present.

Using DNA sequencing methods they were able to pin down the underlying cause of the condition to mutations in the AQP5 gene, which encodes a water channel protein known as aquaporin 5.
"Aquaporins are a family of proteins known as 'the plumbing system for cells' as they form pores which allow water to flow through cells rapidly," Kelsell said.

"We knew aquaporin 5 was present in high amounts in the sweat glands, salivary glands and tear ducts - routes by which the body loses water. Here we've demonstrated it is also found in the skin, with higher amounts in the hands and feet," he said.

"The AQP5 gene mutation appears to result in a protein that has a wider channel than usual, forming a bigger pore in the cell membrane allowing more water to permeate it," said co-author Dr Diana Blaydon, also from the Blizard Institute.
Further work is needed to understand exactly how the mutations identified and the associated changes in the skin barrier lead to NEPPK, researchers said.