Venus Williams' revelation that she is coping with a rare auto-immune disorder shocked the tennis world, but the seven-time Grand Slam champion insisted she will not quit.
In an interview on ABC's "Good Morning America," the 31-year-old American said she was relieved that doctors had finally diagnosed her Sjogren's Syndrome, a condition in which the body's immune system attacks its own healthy tissues.
"I think I've had issues with Sjogren's for a while," Williams said. "It just wasn't diagnosed.
"The good news for me is now I know what's happening."
Williams withdrew abruptly from the US Open on Wednesday, shortly before she was to tackle Wimbledon semi-finalist Sabine Lisicki for a third-round berth.
She had already pulled out of two tournaments in recent weeks because of illness.
Williams said she "absolutely" plans to return to tennis, a sport in which she and her younger sister Serena caused a sensation when they burst on the scene as teenagers.
Sometimes controversial, always colorful, they have been a dominant force in women's tennis.
Serena Williams, winner of 13 Grand Slam titles, recently returned from an 11-month absence with a litany of health concerns, including dangerous blood clots in her lungs.
"If you think about their story (Serena and Venus Williams), I think we take it for granted," America's former world number one Andy Roddick said. "A lot of times they've drawn a lot of criticism. But, trust me, five years, when they're gone, everyone is going to miss them.
"Everyone is going to realize they're going to be living legends for the rest of their lives. Two girls from Compton dominating tennis, that's not an everyday story."
Symptoms of Sjogren's, which can be triggered by an infection, can include dryness in the mouth and eyes, joint and muscle inflammation, and fatigue.
"I had trouble with stamina," Williams said, adding that she was diagnosed with exercise-induced asthma four years ago.
It wasn't until she developed more symptoms that a more accurate diagnosis was made.
"I had swelling and numbness and fatigue, which was really debilitating. I just didn't have any energy," Williams said. "And it's not that you don't have energy - you just feel beat up."
Williams said it was a heartbreaking decision to pull out of the US Open, which was just her fourth tournament of the year.
"I just felt like, 'Okay, I could walk out on the court. I'm a tough woman, I'm a tough athlete, I've played through a lot of things.'
"But what kind of match it would be?" she said. "It was a tough decision, but at the same time I've had to come to accept what I'm going through."
Having a diagnosis, Williams said, at least gives her a means to manage her health, even though there is no cure for Sjogren's syndrome.
"Sjogren's is something you live with your whole life," Williams said. "The good news for me is now I know what's happening after spending years not knowing. I feel like I can get better and move on."