Recent research suggests that genetics plays an important role; however, no specific "lupus gene" has been identified yet. Studies suggest that several different genes may be involved in determining a person's likelihood of developing the disease, which tissues and organs are affected, and the severity of disease. However, scientists believe that genes alone do not determine who gets lupus and that other factors also play a role. Some of the factors scientists are studying include sunlight, stress, certain drugs, and infectious agents such as viruses.
In lupus, the body's immune system does not work as it should. A healthy immune system produces proteins called antibodies and specific cells called lymphocytes that help fight and destroy viruses, bacteria, and other foreign substances that invade the body. In lupus, the immune system produces antibodies against the body's healthy cells and tissues. These antibodies, called autoantibodies, contribute to the inflammation of various parts of the body and can cause damage to organs and tissues. The most common type of autoantibody that develops in people with lupus is called an antinuclear antibody (ANA) because it reacts with parts of the cell's nucleus (command center). Doctors and scientists do not yet understand all of the factors that cause inflammation and tissue damage in lupus, and researchers are actively exploring them.
Symptoms of Lupus
Each person with lupus has slightly different symptoms that can range from mild to severe and may come and go over time. However, some of the most common symptoms of lupus include painful or swollen joints (arthritis), unexplained fever, and extreme fatigue. A characteristic red skin rash-the so-called butterfly or malar rash-may appear across the nose and cheeks. Rashes may also occur on the face and ears, upper arms, shoulders, chest, and hands. Because many people with lupus are sensitive to sunlight (called photosensitivity), skin rashes often first develop or worsen after sun exposure.
Common Symptoms of Lupus
Other symptoms of lupus include chest pain, hair loss, anemia (a decrease in red blood cells), mouth ulcers, and pale or purple fingers and toes from cold and stress. Some people also experience headaches, dizziness, depression, confusion, or seizures. New symptoms may continue to appear years after the initial diagnosis, and different symptoms can occur at different times. In some people with lupus, only one system of the body, such as the skin or joints, is affected. Other people experience symptoms in many parts of their body. Just how seriously a body system is affected varies from person to person.
The following systems in the body also can be affected by lupus:
Diagnosing lupus can be difficult. It may take months or even years for doctors to piece together the symptoms to diagnose this complex disease accurately. Making a correct diagnosis of lupus requires knowledge and awareness on the part of the doctor and good communication on the part of the patient. Giving the doctor a complete, accurate medical history (for example, what health problems you have had and for how long) is critical to the process of diagnosis. This information, along with a physical examination and the results of laboratory tests, helps the doctor consider other diseases that may mimic lupus, or determine if the patient truly has the disease. Reaching a diagnosis may take time as new symptoms appear.
No single test can determine whether a person has lupus, but several laboratory tests may help the doctor to make a diagnosis. The most useful tests identify certain autoantibodies often present in the blood of people with lupus. For example, the antinuclear antibody (ANA) test is commonly used to look for autoantibodies that react against components of the nucleus, or "command center," of the body's cells. Most people with lupus test positive for ANA; however, there are a number of other causes of a positive ANA besides lupus, including infections, other autoimmune diseases, and occasionally as a finding in healthy people. The ANA test simply provides another clue for the doctor to consider in making a diagnosis. In addition, there are blood tests for individual types of autoantibodies that are more specific to people with lupus, although not all people with lupus test positive for these and not all people with these antibodies have lupus. These antibodies include anti-DNA, anti-Sm, anti-RNP, anti-Ro (SSA), and anti-La (SSB). The doctor may use these antibody tests to help make a diagnosis of lupus.
Some tests are used less frequently but may be helpful if the cause of a person's symptoms remains unclear. The doctor may order a biopsy of the skin or kidneys if those body systems are affected. Some doctors may order a test for anticardiolipin (or antiphospholipid) antibody. The presence of this antibody may indicate increased risk for blood clotting and increased risk for miscarriage in pregnant women with lupus. Again, all these tests merely serve as tools to give the doctor clues and information in making a diagnosis. The doctor will look at the entire picture-medical history, symptoms, and test results-to determine if a person has lupus.
Other laboratory tests are used to monitor the progress of the disease once it has been diagnosed. A complete blood count, urinalysis, blood chemistries, and the erythrocyte sedimentation rate (ESR) test can provide valuable information. Another common test measures the blood level of a group of substances called complement. People with lupus often have increased ESRs and low complement levels, especially during flares of the disease. X rays and other imaging tests can help doctors see the organs affected by SLE.