Lupus is a chronic autoimmune disease where the body’s immune system becomes hyperactive and attacks normal tissue. It can lead to the destruction of the kidney, heart, brain, spine and lungs.
The disease is treated by drugs, and by chemotherapy designed to suppress the action of the immune system.
According to the BBC concerns about the 23-year-old’s health were first raised in 2013, when she cancelled a tour of Asia and Australia.
The singer has revealed her break was “really about” her lupus diagnosis, adding: “I could have had a stroke.”
Speaking to Billboard magazine the pop star was scathing about gossip websites that suggested she was addicted to drugs.
“I wanted so badly to say: ‘You guys have no idea. I’m in chemotherapy. You’re assholes’.”
“I locked myself away until I was confident and comfortable again.”
The immune disease affects around 1.5 million Americans, with women between the ages 15 and 44 making up the largest percentage of diagnosis.
Selena’s diagnosis has brought much needed attention to a disease that affects over 5 million people worldwide.
Gomez, who began her career as a child star on programmes like Barney and Friends and Wizards of Waverley Place, is currently promoting her new album Revival.