Sunlight may cause some women to develop autoimmune diseases, including forms that can weaken muscles or cause rashes, according to new research.

A media release from the National Institute of Environmental Health Sciences said the conditions are known as myositis, dermatomyositis and polymyositis.

In general, autoimmune diseases are those that cause the body to attack itself.

According to Dr. Frederick Miller, women are more likely than men to develop many autoimmune diseases, but the reasons for this have not been clear.

"We only found the association between UV exposure and dermatomyositis in women and not in men, and it could be that inherent differences in how women and men respond to UV radiation may play a role in the development of certain autoimmune diseases," he said.

Other studies have shown that that female mice develop more skin inflammation after UV light exposure.

The results were based on information on 380 patients with some form of myositis.

The study was published in the August issue of Arthritis & Rheumatism.