What you need to know about the mysterious illness that's causing Selena Gomez to go on hiatus

Last year, Selena Gomez revealed she had been diagnosed with lupus, an autoimmune disease that required the singer to go through chemotherapy.

And now, after spending months traveling around on her Revival concert tour, Gomez announced that she's taking some time off to focus on her health.

The singer told People that she's been suffering from "anxiety, panic attacks and depression," which can be side effects of the disease.

"I want to be proactive and focus on maintaining my health and happiness and have decided that the best way forward is to take some time off," Gomez said in a statement.

Lupus is a chronic autoimmune disease that can "affect people in different ways," Gomez said.

According to the Lupus Foundation of America, the disease can damage any part of the body, including joints, skin and internal organs, and causes the immune system to be unable to tell the difference between foreign invaders and healthy tissues.

Lupus therefore creates antibodies that can kill healthy tissue, in addition to causing inflammation, damage, and pain throughout the body. In other words, it causes the immune system to be overactive.

The disease isn't contagious, and it tends to affect women more than men, though most people develop the disease between the ages of 15 and 44.

Lupus can cause a myriad of symptoms, beyond those Gomez is suffering from.

Kenneth M. Farber, co-CEO and co-president of the Lupus Research Alliance, told People that the disease is "sometimes very misunderstood."

"It is not commonly known that depression, anxiety, and panic attacks can be side effects of lupus," Farber said.

The disease can also bring about a ton of other symptoms, including swollen joints, fever, fatigue, rashes, chest pain, hair loss, anemia, and more.

There is no cure for lupus at the present time.

Yet, while there isn't yet a cure for the disease, there are a bunch of different treatment options for lupus.

The disease is treated by a variety of different medicines, ranging from mild to strong, according to the Lupus Foundation of America.

The drugs are geared towards reducing inflammation, suppressing the immune system, preventing flare ups, controlling symptoms and minimizing organ damage.

A number of other celebrities have opened up about their struggle with lupus, as well.

Lady Gaga told CNN's Larry King in 2010 that she tested "borderline positive" for lupus, though she hasn't suffered from any symptoms. However, she noted that the disease runs in her family.

Nick Cannon revealed in 2012 that he has lupus, and even spoke with the Lupus Foundation of America about living with the disease in a 2014 interview.

Additionally, singers Toni Braxton and Seal also suffer from the disease, and have spoken about their struggles.