Supplement: Ultraviolet Light and Dermatomyositis

Dermatomyositis is a connective-tissue disease that is characterized by inflammation of the skin and the muscles. Exposure to sunlight, either occupationally or recreationally, is anecdotally associated with flare-ups and even with onset of the condition in some cases. Inspired by those stories, Frederick Miller, chief of the environmental autoimmunity group at the National Institutes of Health, and his colleagues performed the first worldwide evaluation of dermatomyositis to determine whether ultraviolet radiation could explain variations in the frequency of disease.

"We did an evaluation of many centers around the world and found that the proportion of patients who have dermatomyositis or the anti-Mi-2 autoantibody strongly correlated with the amount of UV light measured at that location," says Miller. In contrast, the frequency of a...