People who have lupus tend to have an extra sensitivity to the sun called photosensitivity. There are a few different types of lupus, which is considered to be an autoimmune disease. Systemic lupus affects the entire body but cutaneous lupus predominately affects just the skin. Cutaneous lupus is further divided into two groups: discoid lupus erythematosus (DLE) and subacute cutaneous lupus erythematosus (SCLE). The actual cause of lupus is not known but researchers do think they understand why people with lupus react so strongly to sun exposure.
It is common for people with lupus to develop rashes after exposure to the sun. A butterfly rash which appears on the face across the nose and cheeks is the classic lupus rash. People with DLE may develop a “disk-like” rash on sun-exposed skin or those with SCLE may develop a red circular rash on their chest, back and arms that is scaly and raised.
“Patients with lupus are most sensitive to UVA and UVB light,” said Amita Bishnoi, MD, a rheumatologist at Henry Ford Hospital in Detroit. (1)
Why sunlight causes lupus photosensitivity:
According to Dr. Thomas Millard, Research Registrar in Dermatology at St. Thomas Hospital in London, UV light stimulates a type of allergic response on the surface of the skin. Protein antigens, two of which are called “Ro” and “La” react with antibodies such as, “anti-Ro” and “anti-La” which attach themselves to the proteins. White blood cells are then attracted to the skin and attack the skin cells causing a rash to develop. (2)
In addition, research has shown that certain skin cells in lupus patients die off and excessively accumulate. This over-accumulation of dead skin cells contributes to the inflammatory process increasing the rash. “Another recent study found too much nitric oxide may be made in the skin of lupus patients after sun exposure, which may lead to redness and inflammation. It is unknown why any of these mechanisms are more active in patients with lupus.” (2)
Recent research by Vicki Rubin Kelley M.D. has added further knowledge as to why sunlight’s UV rays can trigger cutaneous as well as systemic lupus in some people. Kelley and her colleagues have found through experiments with mice that a damaging substance called Colony Stimulating Factor 1 (CSF-1) is produced when susceptible people’s skin are exposed to the sun. CSF-1 “then recruits and modifies white blood cells, which in turn stimulates the most common form of skin lupus (DLE) in genetically susceptible individuals.” (3) Her desire in future research is to explore ways to block CSF-1 using a topical skin lotion.
It is most important for those suffering from lupus to make sure they have adequate protection from the sun. Use of sunscreen with an SPF above 15, wearing sun protective clothing and following general guidelines to avoid sun during the most intense UV ray radiation times of the mid-day are crucial to avoid stimulating lupus related rashes.
1. Sun exposure and Lupus
2. Sunlight and Lupus
3. Discovery: How Sunlight Triggers Lupus
Sunlight triggers cutaneous lupus through a CSF-1-dependent mechanism in MRL-Fas(lpr) mice. www.ncbi.nlm.nih.gov/pubmed/18981160?dopt=Abstract
Edited by Alison Stanton
Michele is an R.N. freelance writer with a special interest in woman’s health care and quality of care issues. Other articles by Michele are at www.helium.com/users/487540/show_articles