Lupus is an autoimmune disease in which your immune system attacks your own healthy tissue instead of foreign invaders like bacteria and viruses. It can affect the skin, joints, kidneys, brain, heart, and lungs. About 204,000 people in the United States have systemic lupus erythematosus (SLE), the most common form, and 9 out of 10 of them are women.
You don’t “catch” lupus the way you catch a cold. It develops from a combination of genetic vulnerability, hormonal factors, and environmental triggers that together push the immune system into attacking the body’s own cells. No single cause has been identified, which is part of what makes it so difficult to predict or prevent.
What Happens Inside the Body
Normally, when cells die as part of their natural life cycle, your body clears away the debris quickly and quietly. In lupus, that cleanup process is defective. Dead cell remnants accumulate, and the immune system begins to treat them as threats. This activates immune cells that are normally kept dormant, and they start producing antibodies against the body’s own tissues.
Once that process starts, it can target virtually any organ. In roughly half of people with systemic lupus, a major organ like the heart, lungs, kidneys, or brain becomes involved. The kidneys are especially vulnerable. The disease tends to cycle between flares, when symptoms worsen, and quieter periods of remission.
Genetics Set the Stage
Lupus runs in families, but it doesn’t follow a simple inheritance pattern like eye color. Researchers have identified 330 genetic locations associated with increased lupus risk. The vast majority of these, over 90%, are found in non-coding regions of DNA, meaning they don’t change the structure of proteins directly. Instead, they act more like volume knobs, turning immune-related genes up or down in ways that make the immune system more likely to misfire.
The genetic pathways involved include how immune cells activate and differentiate, how the body produces and responds to inflammatory signals (especially a group called type I interferons), and how effectively the body clears dead cells and immune complexes. Some of the strongest genetic risk factors involve genes that regulate complement proteins, which are part of the body’s first-line defense system. When these genes don’t work properly, the immune system loses its ability to clean up after itself.
Having these genetic variants doesn’t guarantee you’ll develop lupus. Most people who carry risk genes never do. But genetics load the gun, and environmental factors pull the trigger.
Why Women Are Far More Affected
Women develop lupus at roughly nine times the rate of men, and the highest-risk group is women of childbearing age, between 15 and 44. That pattern strongly implicates estrogen.
Estrogen generally enhances immune responses, while androgens (male hormones) and progesterone tend to suppress them. In women with lupus, estrogen appears to amplify a specific chain reaction: it increases the activity of a key enzyme in T cells, which then overstimulate B cells into producing antibodies that attack the body’s own tissue. Interestingly, this enzyme doesn’t respond the same way to estrogen in healthy women or in men with lupus, suggesting that the estrogen receptor itself functions differently in women who develop the disease.
This hormonal connection explains why lupus symptoms sometimes fluctuate with the menstrual cycle and why pregnancy can trigger flares.
Environmental Triggers
In someone with genetic susceptibility, certain environmental exposures can set the disease in motion or worsen it once it’s active.
- Sunlight. In up to 80% of lupus patients, UV exposure triggers both skin inflammation and systemic flares, including kidney damage. Research from Dartmouth has shown that UV light hitting the skin activates inflammatory pathways involving a type of white blood cell called neutrophils, which then circulate and cause damage far from the original sun exposure.
- Infections. Epstein-Barr virus, the virus that causes mono, has one of the strongest links to lupus onset. The immune response to certain infections may cross-react with the body’s own proteins, jumpstarting the autoimmune process.
- Medications. Some drugs can cause a temporary form called drug-induced lupus. The most common culprits include isoniazid (a tuberculosis drug), hydralazine (a blood pressure medication), procainamide (a heart rhythm drug), and TNF-alpha inhibitors used for conditions like rheumatoid arthritis. Drug-induced lupus typically resolves after the medication is stopped.
Who Is Most at Risk
Beyond being female, race and ethnicity play a significant role. Black, Hispanic, Asian, and American Indian/Alaska Native populations are affected at higher rates than white populations. Black and American Indian/Alaska Native women are two to three times more likely than white women to develop lupus. These disparities reflect a combination of genetic factors, differences in access to early diagnosis, and potentially different environmental exposures.
Recognizing the Symptoms
Lupus is notoriously difficult to pin down because its symptoms overlap with many other conditions. The most common early signs include persistent fatigue, unexplained fevers, and joint pain with stiffness and swelling. Many people also develop a butterfly-shaped rash across the cheeks and bridge of the nose that worsens with sun exposure, though not everyone with lupus gets this rash.
Other symptoms include shortness of breath, chest pain, headaches, confusion, memory problems, and fingers or toes that turn white or blue in cold temperatures or during stress (a condition called Raynaud’s phenomenon). Hair loss without scarring and mouth ulcers are also common. The pattern of symptoms varies enormously from person to person, which is one reason diagnosis often takes years.
How Lupus Is Diagnosed
There is no single test for lupus. Diagnosis relies on a combination of blood work and clinical symptoms. The first screening step is a blood test for antinuclear antibodies (ANA). A positive ANA result doesn’t confirm lupus on its own, since many healthy people test positive, but a negative result makes lupus very unlikely.
If ANA is positive, doctors use a scoring system that assigns points across multiple categories: skin involvement, joint inflammation, kidney function, blood cell counts, neurological symptoms, and specific antibody markers. A score of 10 or more, with at least one clinical symptom present, leads to a lupus classification. Kidney involvement through biopsy carries the highest weight in this scoring system, reflecting how central kidney disease is to the severity of lupus.
The Different Types of Lupus
Systemic lupus erythematosus is the most common and most serious form, capable of affecting multiple organ systems. Some people develop only skin symptoms, a form called discoid lupus, which causes chronic round or coin-shaped rashes that can scar. Discoid lupus sometimes, but not always, progresses to the systemic form.
Drug-induced lupus, as mentioned, is triggered by specific medications and is generally milder. It rarely involves the kidneys or brain and typically clears up within weeks to months of stopping the offending drug. Neonatal lupus is a rare condition affecting newborns of mothers who carry certain antibodies. It’s usually temporary, though it can occasionally cause serious heart problems in the infant.