Working with a laptop on your lap could lead to "toasted skin syndrome," say Swiss researchers who recommend placing a heat shield under such computers.

The condition is characterized by discoloured sponge-patterned skin caused by long-term heat exposure, according to medical reports.

Researchers at University Hospital Basel in Switzerland chronicle the case of a 12-year-old boy in a study released Monday in the peer-reviewed journal Pediatrics.

The youngest of 10 patients reported with the condition in medical journals since its first description in 2004, the boy had mottled skin on his left thigh after playing computer games a few hours every day for several months.

"He recognized that the laptop got hot on the left side. However, regardless of that, he did not change its position," the researchers wrote.

Swiss researchers say using your laptop on your lap could lead to 'toasted skin syndrome.' They recommend using a heat barrier. (CBC) Another case involved a Virginia law student who sought treatment for the mottled discolouration on her leg.

Dr. Kimberley Salkey, who treated the young woman, was stumped until she learned the student spent about six hours a day working with her computer propped on her lap. The temperature underneath registered 52 C.

The condition — which can also be caused by the long-term use of heating pads — is usually harmless but it can make the skin permanently dark.

While they don't cite skin cancer cases linked to laptop use, the researchers caution that it could cause damage leading to such cancers.

Computer manufacturers generally warn users against placing laptops on laps or exposed skin for extended periods of time because of the risk for burns.

With files from The Associated Press