Back in 2015 Selena Gomez announced to the public her diagnosis of Lupus, an inflammatory disease caused when the immune system attacks its own tissues. On Thursday, September 14, she shocked millions of her fans revealing that she had received a kidney transplant from one of her best friends.

The pop star took it to Instagram posting a photo of her and her best friend, Francia Raisa, holding hands lying in their hospital beds.

In her post Gomez explains why she went under the radar during the summertime, not promoting her work.

“I’m very aware some of my fans had noticed I was laying low for part of the summer and questioning why I wasn’t promoting my new music, which I was extremely proud of.”

During the summer she found out she needed the transplant due to her disease, as well as time to recover to improve her health.

“It was what I needed to do for my overall health,” Gomez said.

Even though people have two kidneys, they only need one to live. There are about 16,000 transplants per year due to the long waiting list for a kidney transplant. Receiving a kidney when put on a waiting list is like winning the lottery, very rare. Finding a donor that is a match can be difficult, ideal matches are usually family members. In Gomez’s case it was her best friend, Raisa.

“And finally, there aren’t words to describe how I can possibly thank my beautiful friend Francia Raisa. She gave me the ultimate gift and sacrifice by donating her kidney to me.”

Her fans were overjoyed with the fact that she is well and one step closer to recovery in her medical journey, but they also had many questions of concern.

The singer continues to live her everyday life and gradually recover hoping people are more aware of the disease.

“Lupus continues to be very misunderstood,” Gomez wrote. “but progress is being made.”