The number of people diagnosed with lupus has more than tripled over the past four decades. This may simply indicate a greater degree of doctor training in recognizing the syndrome.
About 90% of lupus patients are women, most diagnosed when they are in their childbearing ages. Hormones may be an explanation. After menopause, women are only 2.5 times as likely as men to contract SLE. Flares also become somewhat less common after menopause in women who have chronic SLE.
African-Americans are three to four times more likely to develop the disease than Caucasians and to have severe complications. Hispanics and Asians are also more susceptible to the disease.
A family history plays a strong role in SLE. A brother or sister of a patient with the disorder has 20 times the risk as someone without an immediate family member with SLE.
The disease is rare in childhood. When it does occur, it is often associated with thrombotic thrombocytopenia purpura, a condition resulting from abnormally low levels of blood platelets. SLE in children may also be caused by certain medications, including minocycline and zafirlukast.
Rheumatoid Arthritis. Studies have investigated the relationship among hormones, SLE, and rheumatoid arthritis, another autoimmune disease. Higher levels of estrogen are associated with SLE, while lower levels are associated with rheumatoid arthritis. Some research suggests that some patients, in fact, progress from one disease to the other, and that such transitions occur during major hormonal shifts, such as the onset of menopause or pregnancy.
Many prescription drugs can cause lupus-like skin symptoms. These include high blood pressure (hypertension) medications, including hydrochlorothiazide, angiotensin-converting-enzyme inhibitors, and calcium-channel blockers. About 40 different drugs have been linked to lupus onset. Anyone diagnosed with cutaneous lupus erythematosus should be sure to tell their doctors all the medications (including herbs and supplements) that they are taking.
Smoking. Smoking may be a risk factor for triggering SLE and can increase the risk for skin and kidney problems in women who have the disease.
In genetically susceptible people, there are various external factors that can provoke an immune response. Possible SLE triggers include colds, fatigue, stress, chemicals, sunlight, and certain drugs.
Viruses. Patients with SLE may be more likely to have been exposed to certain viruses than the general population. These viruses include the Epstein-Barr virus (the cause of mononucleosis), cytomegalovirus, and parvovirus-B1. In particular, some research suggests a strong association between Epstein-Barr virus (EBV) and increased risk of lupus, particularly for African-Americans.
Sunlight. Ultraviolet (UV) rays found in sunlight are important SLE triggers. When they bombard the skin, they can alter the structure of DNA in cells below the surface. The immune system may perceive these altered skin cells as foreign and trigger an autoimmune response against them. UV light is categorized as UVB or UVA depending on the length of the wave. Shorter UVB wavelengths cause the most harm.
Chemicals. Clusters of SLE cases have occurred in populations with high exposure to certain chemicals. Chlorinated pesticides and crystalline silica are two suspects. A number of other chemicals are under investigation. However, it is very difficult to determine a causal role for any specific chemicals. (Silicone breast implants have been under intense scrutiny as a possible trigger of autoimmune diseases, including SLE. The weight of evidence to date, however, finds no support for this concern.) Some drugs have been associated with a temporary lupus syndrome (drug-induced lupus), which resolves when these drugs are stopped.
Hormones. Cytokines, major immune factors that are active in SLE, are directly affected by sex hormones. In general, estrogen enhances antibody production, and testosterone reduces antibody production, although their exact role in SLE may be more complicated than that since there are various ways in which each hormone might influence various immune cells. Women with SLE may have lower levels of several active male hormones (androgens), and some men who are affected by SLE may also have abnormal androgen levels.
Premature menopause, and its accompanying symptoms (such as hot flashes), is common in women with SLE. Hormone replacement therapy (HRT), which is used to relieve these symptoms, increases the risk for blood clots and heart problems. It is not clear whether HRT triggers SLE flares. Women should discuss with their doctors whether HRT is an appropriate and safe choice. Guidelines recommend that women who take HRT use the lowest possible dose for the shortest possible time. Women with SLE who have active disease, antiphospholipid antibodies, or a history of blood clots or heart disease should not use HRT.
Oral Contraceptives. Female patients with lupus used to be cautioned against taking oral contraceptives (OCs) due to the possibility that estrogen could trigger lupus flare-ups. However, recent evidence indicates that OCs are safe, at least for women with inactive or stable lupus. Women who have been newly diagnosed with lupus should avoid OCs. Lupus can cause complications in its early stages. For this reason, women should wait until the disease reaches a stable state before taking OCs. In addition, women who have a history of, or who are at high risk for, blood clots (particularly women with antiphospholipid syndrome) should not use OCs. The estrogen in OCs increases the risk for blood clots.
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