How does a lupus rash develop after sun exposure?
A current theory, based on experimental evidence, is that UV light causes skin cells to express particular proteins on their surface. These proteins, including one called “Ro,” may then be the targets of antibodies which latch on to them. The attached antibodies are thought to attract white blood cells which attack the skin cells, leading to the inflammation that causes the rash. 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. Another contributor to the lupus rash may be that too much of the inflammation-promoting substancenitric oxideis made in lupus skin after sun exposure. This then leads to further redness and inflammation. The reasons for these abnormal reactions (beyond a genetic tendency to them) are unknown, but many potentially exc
