Lupus is a difficult disease to diagnose because its symptoms can be vague. And unlike some other diseases, it cannot be diagnosed with a single lab test. However, when certain clinical criteria are met, lab tests can help confirm a diagnosis of lupus. Blood work and other tests can also help monitor the disease and show the effects of treatment.
WebMD takes a look at the uses and limitations of the tests that are commonly used to diagnose and monitor lupus.
You can also help prevent skin reactions, too. The best way is to use sunscreen to protect yourself from the sun's ultraviolet (UV) rays.
Skin Changes From Lupus
You can have skin lupus with or without having full-blown systemic lupus erythematosus (SLE), the most common kind of lupus. Be on the lookout for some of these rashes that can be caused by skin lupus:
Butterfly rash: Called a "malar" rash, this may spread over your nose and cheeks in the shape of a butterfly.
The butterfly rash can be just a faint blush or a very severe, scaly rash. The sun's UV rays can trigger it and make it worse.
Sores and rashes. Some may be coin-shaped (called discoid lupus). Or you may develop red, scaly patches or a red, ring-shaped rash, especially where your skin gets sun or other UV light.
The sores get worse without treatment. They usually don't itch or hurt, but they can cause scarring. If this happens on your scalp, you may get patches of long-term baldness.
Small, red, coin-shaped sores. These are caused by exposure to the sun's UV rays and are called subacute cutaneous lesions. They'll likely appear on your arms, shoulders, neck, or upper torso in patches, like psoriasis.
They don't cause scarring, but they can darken or lighten the skin where they appear.
Other Skin Issues
Lupus may also cause skin problems in areas such as your mouth, scalp, lower legs, and fingers. Here are some skin changes to watch out for:
Mucous membrane lesions. These are sores in the mouth or nose.
Hair loss. In some cases, your immune system may destroy hair follicles and make hair fall out for a time. New hair may sometimes grow in.
A severe lupus flare can also make your hair fragile and brittle. This is most likely around the edge of your scalp.
Purplish spots on lower legs. These happen when the blood vessels in your skin become inflamed and damaged. Theymay show up as small spots or larger knots. They may also show up as lines or spots of red or purple bumps in the folds of your fingernails or on your fingertips.
These spots are called cutaneous vasculitis lesions. They can cause severe damage to skin tissue and gangrene. If you have small black spots on your fingers or toes, let your doctor know right away.
Color changes in fingers and toes. Blood vessels in your fingers and toes can tighten and slow the flow of blood there. The tips of your fingers or toes may turn red, white, or blue in cold weather or a cold room. They may also tingle, hurt, or go numb.
This problem is known as Raynaud's phenomenon. It helps to keep your toes and fingers warm by wearing mittens and thick socks.
Bluish, lacy pattern under the skin. This is known as livedo reticularis. It's likely to appear on your legs, where it can give a "fishnet" look. Like Raynaud's, it tends to be worse in cold weather.