Sunlight triggers attack on organs.

• Position: Lupus

A variant of the human gene for tumor necrosis factor-alpha (TNF-alpha) as the cause for photosensitivity in lupus patients has been identified by physicians at the University of Pennsylvania School of Medicine, Philadelphia. This discovery not only will help in curtailing photosensitivity, but advance research on treating this potentially damaging symptom and possibly point to one of the genetic causes of lupus.

Victoria Werth, associate professor of dermatology and medicine, and Kathleen E. Sullivan, associate professor of pediatrics, identified a variant of the TNF-alpha promoter that demonstrated increased activity when exposed to sunlight. This is crucial to understanding photosensitivity and lupus because TNF-alpha has been shown to stimulate apoptosis, the process of cellular death. As skin cells die, intracellular proteins move to the cells' surfaces where they stimulate an immune reaction. The immune system makes new antibodies against these proteins and triggers further inflammation, causing the body to attack its own internal organs--just from exposure to sunlight.

A large percentage of patients with subacute cutaneous lupus erythematosus (SCLE), a highly photosensitive form of the disease, has one or even...