Pop singer Selena Gomez announced yesterday that after laying low all summer, she had a kidney transplant, donated by her very best friend. In an Instagram post of Gomez with her friend, Francia Raisa, the 25-year-old explained that she needed a kidney transplant because of her struggle with lupus, and had spent the last few months recovering. The heartwarming and ultimately life-saving story went viral on Thursday, both updating Gomez’s fans on her condition and also drawing attention to her lupus diagnosis.

Gomez first opened up about being diagnosed with lupus in 2013. She decided to take some time off from her career to take care of her health, telling CNN, “I’ve discovered that anxiety, panic attacks, and depression can be side effects of lupus, which can present their own challenges.”

Gomez isn’t alone in her struggle. According to the Lupus Research Alliance, 90 percent of adults with lupus are women, and mostly between the ages of 15 and 44. African-American women are three times more likely than white women to have lupus, while Asian-American and Latina women are twice as likely to have lupus than white women. Native women are at higher risk than white women as well.

All of this means that millennials, particularly millennial women of color, are one among the highest risk groups for lupus right now. So, what is it?

What exactly is lupus, anyway?

Around 1.5 million Americans are living with lupus, according to the Lupus Foundation of America, and it’s very difficult for doctors to properly diagnose. Lupus is an autoimmune disease, which means the body essentially turns on itself and antibodies attack healthy substances in the body, instead of just harmful invaders like infections. It’s also a chronic illness, and can attack any part of the body, including skin, joints, and internal organs.

The list goes on: People with lupus can also experience hair loss and extreme fatigue. Lupus can also lead to strokes. All of the attacks on the body lead to severe pain and life-threatening damage to the body, which is why Gomez needed a new kidney.

When lupus damages the kidneys, it’s called lupus nephritis and comes with a host of painful symptoms. The Lupus Foundation of America explains that at first, lupus nephritis won’t cause any symptoms, but can eventually lead to blood in the urine, swollen extremities, legs, hands, and even eyelids. About 60 percent of people who have lupus have lupus nephritis, according to the Foundation.

What is the treatment?

Treatment for lupus can be complicated, and depends on a patient’s particular symptoms, according to the Mayo Clinic, and the disease is not curable. There are a variety of different medications that can be used to treat lupus, and patients typically have to make frequent doctor’s appointments. Because lupus can be so exhausting, people with lupus will need to sleep and rest more than people who don’t.

Gomez also underwent chemotherapy to treat her lupus, she told Billboard in 2015. While we usually associate chemotherapy with cancer treatment, certain chemotherapy medications can also effectively treat some of the symptoms and health issues caused by Lupus.

Though Lupus is a painful and exhausting disease, people living with Lupus can still live full lives, as Gomez has demonstrated. Though she’s had to take time away from work and the spotlight multiple times as she copes with Lupus, she has continued to make music, tour, and everyone’s favorite hobby: troll Justin Bieber.

Do you have thoughts on Selena Gomez’s kidney transplant from her best friend? Tell us on Twitter @BritandCo.

(Photos via Getty)