Butterfly rash (lupus) is an autoimmune disease where the immune system mistakenly attacks the body's own tissues and cells. It can affect the skin, joints, kidneys, gastrointestinal system, lungs, nervous system, mucous membranes, blood vessel walls, and other tissues or organs.

In butterfly rash, there are mutations in genes that code for structural proteins. This gene mutation alters how the body produces proteins that help bind and strengthen the skin. Because the layers of skin cannot bind normally, this makes the skin more prone to blistering. Blisters on the palms and soles are the most typical symptom, but in more severe subtypes, blistering and rashes can appear all over the body.