The chronic skin condition psoriasis has been linked to a higher risk for developing Type 2 diabetes and high blood pressure, say researchers who think inflammation could be to blame.

Psoriasis, which causes red, scaly patches on the skin, affects between one and three per cent of the population, says the team from Harvard Medical School and Brigham and Women's Hospital in Boston. 

In the April issue of Archives of Dermatology, Dr. Abrar Qureshi and his colleagues report that women were 63 per cent more likely to develop Type 2 diabetes and 17 per cent more likely to develop hypertension than those who were psoriasis-free.

The study looked at 78,061 female nurses, most of whom were white, and who were free of diabetes and high blood pressure at the start of the 14-year study.

During that time, 1,813 women or 2.3 per cent were diagnosed with psoriasis. A total of 1,560 (two per cent) developed diabetes and 15,724 (20 per cent) developed hypertension.

More than 'simply a skin disease'

The link between psoriasis and the other diseases remained strong after taking age, body mass index and smoking into account.

"These data illustrate the importance of considering psoriasis a systemic disorder rather than simply a skin disease," the study's authors concluded in the journal.

"Further research is needed to better understand the mechanisms underlying these associations and to find out whether psoriasis therapy can reduce the risk for diabetes and hypertension."

Inflammation, a risk factor for high blood pressure that may also contribute to insulin resistance in pre-diabetes, could explain the link, the researchers said.

Another possibility is that steroid or other treatments for psoriasis may promote the development of diabetes of hypertension, but no information on psoriasis-related therapy was available, they noted.

Ciclosporin, a drug used to treat moderate to severe psoriasis, had been linked to high blood pressure, the UK Psoriasis Association said in a statement on its website.

Also unclear is the effect therapy for psoriasis might have on the potential for developing Type 2 diabetes, said Dr. William Eaglstein of Stiefel Laboratories in Palo Alta, Calif., and Dr. Jeffrey Callen of University of Louisville, Ky., in a journal commentary.

Qureshi and the editorial writers have been consultants or speakers for several pharmaceutical companies.