How does lupus affect the skin?

Approximately two-thirds of people with lupus will develop some type of skin disease, called cutaneous lupus erythematosus. Skin disease in lupus can cause rashes or sores (lesions), most of which will appear on sun-exposed areas such as the face, ears, neck, arms, and legs.
40-70 percent of people with lupus will find that their disease is made worse by exposure to ultraviolet (UV) rays from sunlight or artificial light.
A dermatologist, a physician who specializes in caring for the skin, should treat lupus skin rashes and lesions. He or she will usually examine tissue under a microscope to determine whether a lesion or rash is due to cutaneous lupus: taking the tissue sample is called a biopsy.
The Forms of Cutaneous Lupus
Lupus skin disease can occur in one of three forms:
1.    Chronic cutaneous (discoid) lupus
2.    Subacute cutaneous lupus
3.    Acute cutaneous lupus.
Chronic cutaneous lupus (discoid lupus) appears as disk-shaped, round lesions. The sores usually appear on the scalp and face but sometimes they will occur on other parts of the body as well.
Approximately 10 percent of people with discoid lupus later develop lupus in other organ systems, but these people probably already had systemic lupus with the skin rash as the first symptom.
Discoid lupus lesions are often red, scaly, and thick. Usually they do not hurt or itch. Over time, these lesions can produce scarring and skin discoloration (darkly colored and/or lightly colored areas). Discoid lesions that occur on the scalp may cause the hair to fall out. If the lesions form scars when they heal, the hair loss may be permanent.
Cancer can develop in discoid lesions that have existed for a long time. It’s important to speak with your doctor about any changes in the appearance of these lesions.
Discoid lupus lesions can be very photosensitive so preventive measures are important:
•    Avoid being out in the sunlight between the hours of 10 a.m. and 4 p.m.
•    Use plenty of sunscreen when you are outdoors
•    Wear sun-protective clothing and broad-brimmed hats
•    Limit the amount of time spent under indoor fluorescent lights
Subacute cutaneous lesions may appear as areas of red scaly skin with distinct edges or as red, ring-shaped lesions. The lesions occur most commonly on the sun-exposed areas of the arms, shoulders, neck, and body. The lesions usually do not itch or scar, but they can become discolored. Subacute cutaneous lesions are also photosensitive so preventive measures should be taken when spending time outdoors or under fluorescent lights.
Acute cutaneous lupus lesions occur when your systemic lupus is active. The most typical form of acute cutaneous lupus is a malar rash–flattened areas of red skin on the face that resemble a sunburn. When the rash appears on both cheeks and across the bridge of the nose in the shape of a butterfly, it is known as the "butterfly rash." However, the rash can also appear on arms, legs, and body. These lesions tend to be very photosensitive. They typically do not produce scarring, although changes in skin color may occur.