What causes lupus?
Many (but not all) scientists believe that lupus develops in response to a combination of factors both inside and outside the body, including hormones, genetics, and environment.
Hormones are the body’s messengers. They regulate many of the body’s functions. Because nine of every 10 occurrences of lupus are in females, researchers have looked at the relationship between estrogen and lupus. While men and women both produce estrogen, its production is much greater in females. Many women have more lupus symptoms before menstrual periods and/or during pregnancy when estrogen production is high. This may indicate that estrogen somehow regulates the severity of lupus. However, no causal effect has been proven between estrogen, or any other hormone, and lupus. And, studies of women with lupus taking estrogen in either birth control pills or as postmenopausal therapy have shown no increase in disease activity.
No gene or group of genes has been proven to cause lupus. Lupus does, however, appear in certain families, and certain genes have been identified as contributing to the development of lupus, but these associations alone are not enough to cause the disease. This is especially evident with twins who are raised in the same environment and have the same inherited features yet only one develops lupus. Although, when one of two identical twins has lupus, there is an increased chance that the other twin will also develop the disease (25 percent chance for identical twins; 2-3 percent chance for fraternal twins). Lupus can develop in people with no family history of lupus, but there are likely to be other autoimmune diseases in some family members.
Certain ethnic groups (people of African, Asian, Hispanic/Latino, Native American, Native Hawaiian, or Pacific Island descent) have a greater risk of developing lupus, which may be related to genes they have in common.
Most researchers today think that an environmental agent, such as a virus or possibly a chemical, randomly encountered by a genetically susceptible individual, acts to trigger the disease. Researchers have not identified a specific environmental agent as yet but the hypothesis remains likely. While the environmental elements that can trigger lupus and cause flares aren’t fully known, the most commonly cited are ultraviolet light (UVB in particular); infections (including the effects of the Epstein-Barr virus), and exposure to silica dust in agricultural or industrial settings.
Other examples of known environmental triggers include:
- Ultraviolet rays from the sun
- Ultraviolet rays from fluorescent light bulbs
- Sulfa drugs, which make a person more sensitive to the sun, such as: Bactrim® and Septra® (trimethoprim-sulfamethoxazole); sulfisoxazole (Gantrisin®); tolbutamide (Orinase®); sulfasalazine (Azulfidine®); diuretics
- Sun-sensitizing tetracycline drugs such as minocycline (Minocin®)
- Penicillin or other antibiotic drugs such as: amoxicillin (Amoxil®); ampicillin (Ampicillin Sodium ADD-Vantage®); cloxacillin (Cloxapen®)
- Cold or a viral illness
- Emotional stress, such as divorce, illness, death in the family, or other life complications
- Anything else that causes stress to the body such as surgery, physical harm, pregnancy, or giving birth
Seemingly unrelated factors can also trigger the onset of lupus in a susceptible person. Scientists have noted some common features, including:
- Exposure to the sun
- Drugs taken to treat an illness