Photosensitivity or abnormal light sensitivity is very complex and is a major symptom of lupus. The American College of Rheumatology (ACR) loosely defines photosensitivity as "a skin rash as a result of unusual reaction to sunlight." Beyond skin rashes that can develop, exposure to the sun can cause those living with lupus to experience increased disease activity with symptoms such as joint pains, weakness, fatigue and fever. Two-thirds of people with lupus have increased sensitivity to ultraviolet rays, either from sunlight or from artificial inside light, such as fluorescent light -- or both.

Normally, skin and other cells that are sufficiently damaged die through a process known as programmed cell death, or "apoptosis." The body then gets rid of the dead cells. But in lupus, apoptosis in the skin seems to occur more often than it should, which may in turn lead to more inflammation and other complications. In addition to worsening of skin lupus lesions, many patients also experience more generalized skin or systemic reactions to light that are not their typical skin lupus.

According to the ACR, photosensitivity in lupus is determined by clinical examination or by patient history of unusual reaction to sunlight. It is important that physicians are able to recognize the varied manifestations of photosensitivity to ensure proper management of lupus.

Now, a new, small study conducted by Victoria P. Werth, MD and colleagues at the University of Pennsylvania sheds new light on photosensitivity among people with lupus. The study, published in the Journal of the American Academy of Dermatology, characterizes frequency and types of abnormal responses to sunlight in patients with different types of lupus, as well as the association of these reactions with systemic lupus. A pilot study to examine different cell types and numbers of these cells in the skin of patients with and without systemic reactions to light was also performed.

While the pathophysiology of photosensitivity is likely to vary depending on the type of reaction(s) experienced by patients, the researchers explain that defining what is meant by photosensitivity is important in evaluating the effectiveness of treatments that may impact this important problem and in further recognizing the symptoms that fulfill criteria for photosensitivity in lupus patients.

The Lupus Foundation of America is dedicated to finding new ways to better understand and treat lupus, and we thank Dr. Werth and her colleagues for their continuous efforts to help solve the cruel mystery of lupus.

More about this study

In the study conducted by Dr. Werth and her colleagues, 83% of lupus patients reported having some form of photosensitivity. Overall, worsening of skin lupus in response to sunlight was reported by 69% of the group. Many people reported early transient skin lupus lesions that occurred after a few hours to a day and then resolve within a week, while others had lesions that occurred early after sun exposure, but persisted for a few weeks to months. About 10% of people noted the worsening of skin lupus in response to sun happens only after a number of days. 60% of patients who felt their skin lupus worsened after sun exposure also had other reactions to the sun. Some patients report a transient skin eruption after sun exposure that was not their typical skin lupus, termed polymorphous light eruption (PMLE)-like reaction. Others had a generalized sense of itching, stinging, or burning of skin that affected their skin, but without a skin eruption. Lastly, 33% of patients had systemic symptoms after sun exposure, including joint pain, weakness, fatigue, or headaches. These different types of reactions can occur sometimes in the same patient.

The researchers found no relationship between race and any photosensitivity presentation. Subjects with generalized cutaneous reactions (PMLE-like and sting/itch) and those who experienced sun-induced systemic symptoms of joint pain, weakness, fatigue or headaches, tended to have more systemic lupus disease activity. The study noted a novel subset of CLE patients who experienced systemic reactions after sun exposure despite not meeting criteria for SLE. A small study of a subset of the photosensitive patients had a greater density of specific types of inflammatory cells in normal skin compared to those without systemic symptoms.

The results are based on self-report by patients using a photosensitivity questionnaire that is currently undergoing further validation. The patients predominantly had cutaneous lupus, with or without systemic lupus. The findings in patients with primarily systemic forms of lupus may be different.

Characterization of clinical photosensitivity in cutaneous lupus erythematosus
Kristen Foering, Aileen Y. Chang, Evan W. Piette, Andrew Cucchiara, Joyce Okawa, Victoria P. Werth.
Journal of the American Academy of Dermatology. 2013 August 1.