CHICAGO: People with a severe form of the skin disease Psoriasis are likely to die at a younger age than their healthy peers, according to a study.

The illness appears to shorten life expectancy by about five per cent in patients most afflicted, reducing more than three years of the life expectancy of a man and more than four of a woman, compared to people who don't have the condition.

The shortened life expectancy is comparable to what is seen in patients with a long history of hypertension, the researchers said on Monday.

"This study underscores just how serious this condition is," said Joel Gelfand, assistant professor of dermatology at the University of Pennsylvania School of Medicine in Philadelphia and lead author on the paper.

It's more than a disfiguring skin condition. It's an immunological illness that has a profound impact on the health and well-being of people who suffer with it and one that will probably cut their life short.

"Patients need to get regular health check-ups and follow a healthy lifestyle."

Psoriasis is a common, but incurable, skin disease characterised by outbreaks of scaly red patches of skin. The lesions can appear on any part of the body. Treatments include steroid medications and treatment with ultraviolet light.

The condition is thought to be at least partly genetic, and involves some immune dysfunction. It has been linked to depression, higher rates of smoking and alcohol use and diseases such as obesity, cardiovascular disease and some forms of cancer.