L93.1: Subacute cutaneous lupus erythematosus

The immune system protects the body from pathogens and foreign substances. The immune system can also destroy cells in the body that have pathologically changed. Some of the immune system’s antibodies can make pathogens and foreign substances visible to the immune system. Other antibodies attack pathogens or foreign substances directly. There are disorders that cause the immune system’s antibodies to attack the body itself.

Lupus involves the antibodies attacking the body’s own connective tissue. There are different forms of lupus. With this form of lupus, the antibodies target the connective tissue in the small blood vessels of the skin. Blood vessels transport the blood from the heart to the different tissues and organs in the body, and back again. In so doing, they provide the tissue and organs with oxygen and nutrients, and remove waste substances. The antibodies trigger an inflammation of the small blood vessels. Typical skin changes form as a result. The skin changes can be triggered or made worse by things like sunlight or certain medications.

The skin changes are mainly on the head, back and arms. Larger areas may also be affected. Red, raised patches form on the skin. These patches can be round and about as big as a coin. The skin in these places may be rough or scaly. The affected areas can have a dark red, wavy edge.

The lupus may affect other organs too. For example, the person may then have sore muscles or joints. Other organs, for example the kidneys, may also become affected over time.