How can sunlight trigger skin symptoms in systemic lupus erythematosus?

In systemic lupus erythematosus (SLE), sunlight triggers skin symptoms through a process known as photosensitivity, which is a common clinical manifestation of the disease.12

This reaction is linked to the presence of specific autoantibodies, particularly those known as anti-Ro and anti-La. These antibodies are suspected to play a direct role in the development of skin rashes following exposure to ultraviolet light.1

From a pathological perspective, SLE involves a breakdown of the immune system where the body produces autoantibodies that react with components of its own tissues, such as the nucleic acids and proteins within cell nuclei. When these autoantibodies bind to their targets, they form immune complexes that deposit in tissues, leading to inflammation and injury. Ultraviolet light acts as an environmental stimulus that can trigger or exacerbate this immune response in individuals who have a genetic predisposition to the disorder. Consequently, exposure to sunlight can induce the formation of these damaging complexes in the skin, resulting in the characteristic rashes associated with the disease.312