Thursday, September 13, 2012
Lupus and the Sun
When people ask 'what is lupus?' I'm getting better at explaining the general gyst of it so it makes sense to them, but as to why the sun makes me ill, I still have to resort to my info filed away for reference. This information was taken from a site called PhysiciansforPatients. The page from which I found this information doesn't seem to exist anymore but The Lupus Site is also very good.
Photosensitivity or sensitivity to ultraviolet (UV) light, is a common symptom of lupus. It can take different forms. Some people actually become ill after exposure with nausea, fatigue and headaches. Others may suffer a flare-up with arthritis, alopecia, pleurisy or mucosal ulcerations. The most common problem with UV exposure is the lupus rash. The rash may be limited to just those areas of exposure or it may pop up on different parts of the body.
Researchers at John Hopkins University found that after UV exposure, skin cells die and undergo apoptosis, a clearance mechanism through which the body removes and recycles dead cells. During apoptosis, the dying skin cells transiently express a protein called Ro on their surfaces. Usually the Ro protein is hidden far from the skin surfce deep in the nucleus of the cell where immune cells (lymphocytes) cannot see it. Some lupus patients develop autoantibodies that bind to the Ro antigen. Therefore, after UV exposure, the massive cell death induced in the skin in turn results in massive expression of Ro protein. Then the anti-Ro antibodies that are circulating in the patient's blood and circulating lymphocytes that recognize Ro will migrate to the skin and bind to the Ro protein, generating inflammation in the skin-seen as a rash. This is why many lupus patients who have measureable anti-Ro (also called anti-SSA) antibodies also have problems with rash and sun sensitivity. Not all patients with lupus rashes have anti-Ro antibodies, yet nearly all lupus rashes worsen with sun exposure.
Darkness or hyperpigmentation of the skin occurs in lupus for different reasons. Usually we see patchy dark spots in the same areas that were involved by an active rash that has not gone away, meaning that the bumpiness and scaling and redness of the rash has cleared. What happens at a cellular level is that the inflammatory mediators that cause the rash also turn on pigment production in pigment producing skin cells at the base of the skin called melanocytes. It can take months or years for the extra pigment to be absorbed and cleared from the skin so the post-inflammatory hyperpigmentation tends to stay around longer than the red, bumpy initial rash. An exception to this process may occur in discoid lupus rashes. In discoid rashes, the inflammatory process is more intense and tends to destroy skin cells and skin infrastructure. As a result, the skin scars, leaving behind thin shiny skin devoid of hair follicles, sweat glands, and melanocytes. As a consequence, areas of skin may appear white or colorless, called vitiligo. Since melanocytes cannot migrate back into scarred skin, this form of vitiligo is usually permanent.
There really aren't any therapies to change photosensitivity in lupus patients. Plaquenil is helpful in reducing the risk of a flare-up, but for many the best way is to reduce sun exposure in the first place. The sun is at its zenith point between 11 a.m. and 2 p.m. so limit being exposed during those hours. Otherwise, wear your sunhat and use sunscreen. The hat worn in the picture is from Sunday Afternoons. I love this hat being it is attractive enough to wear in public, has a wide brim with all-around protection and has a tie to keep it on. I've often been asked where I got my hat. I guess there are many people frustrated with the many unpractical sunhats available that either aren't big enough or too easily blow right off.
So we do what we have to do and make the best of it. Think of it as preventing wrinkles down the road. :)