Selena Gomez's Diagnosis: What Is Lupus?
Selena Gomez
Credit: Joe Seer/Shutterstock.com

The pop star Selena Gomez recently announced that she was diagnosed with lupus and underwent chemotherapy for the condition in 2013.

The autoimmune diagnosis was behind her decision to cancel her 2013 tour and spend years out of the spotlight.

"I was diagnosed with lupus, and I've been through chemotherapy. That's what my break was really about. I could've had a stroke," Gomez told Billboard Magazine in a recent interview.

This may be the first time that Gomez fans have heard of the disease. Even so, Gomez, 23, fits the demographic for the autoimmune condition, which tends to strike women of childbearing age. Though doctors don't understand exactly what triggers lupus, they have developed several treatment options — including chemotherapy for the most serious cases. [10 Celebrities With Chronic Diseases]

What is lupus?

Lupus, or systemic lupus erythematosus, is a chronic autoimmune disease in which the body attacks its own cells as if they were harmful invaders. The disease can affect almost any tissue in the body, according to the Lupus Foundation of America. Though there are no precise estimates of the disease's prevalence, up to 1 in 250 women may have the disease, according to the Lupus Foundation of America.

Lupus can be tricky to diagnose because its symptoms are so varied: It can cause skin rashes, light sensitivity and mouth ulcers, while more serious cases can lead to seizures and psychosis, life-threatening kidney problems, pericarditis — an inflammation of the sac that surrounds the heart — and inflammation of the lung lining, called pleurisy, according the Centers for Disease Control and Prevention (CDC). Like other autoimmune diseases, those who contract the disease can also go into remission for years.

Ninety percent of lupus sufferers are women, and most first report symptoms between the ages of 15 and 44, according to the CDC. Nonwhite populations — particularly blacks, though also possibly Native Americans and Hispanics — seem to be both more prone to the disease and more likely to have severe cases, according to a 2001 study by the Arthritis Foundation.

Because it has such a varied presentation, doctors may not initially suspect that a patient has the disease. To diagnose it, doctors look for any of these symptoms and also test the blood for the presence of antinuclear antibodies, or ANAs. This marker reveals that the immune system has mounted an attack against the cell nucleus. However, about 5 percent of the healthy population will test positive for ANA.

Treatments for lupus

One of the most common treatments for mild cases of lupus is a steroid for skin rashes. Oral steroids can be used when internal organs are threatened, according to the Cleveland Clinic.

But Gomez said she underwent chemotherapy, suggesting she has a more serious form of the disease. Though she didn't identify the type of chemotherapy, in the most severe manifestations of lupus, doctors often turn to cyclophosphamide — a powerful chemotherapeutic agent that quiets the immune system. Methotrexate, another chemotherapy agent, can be used for severe cases of skin rashes or arthritis associated with lupus, according to the Cleveland Clinic.

Other forms of treatment include the administration of monoclonal antibodies, which bind to a specific type of antibodies produced by white blood cells that attack the body's cells. For severe cases of lupus, it's important to block the action of these white blood cells, because the antibodies can damage other tissues.

While lupus can be life-threatening, in most cases people have a normal lifespan. A 2015 study in the journal Arthritis and Rheumatology found that about 27 out of 1,000 Native Americans with lupus died from the disease every year. Asians and Hispanics had markedly lower rates, with just 7 out of 1,000 Hispanic patients and 5 out of 1,000 Asian patients dying of the disease every year. Overall, about 10 to 15 percent of those diagnosed with lupus will have a shortened life span as a result of their disease, according to the Lupus Foundation of America.

Gomez isn't the only high-profile celebrity to be diagnosed with the disease. Singers Toni Braxton and Seal both have the disease.

Follow Tia Ghose on Twitterand Google+. Follow Live Science @livescience, Facebook & Google+. Original article on Live Science.