U.S. Tennis star Venus Williams withdrew Wednesday from the U.S. Open after recently being diagnosed with an energy-draining autoimmune disease called Sjogren's syndrome.

The 31-year-old player was forced to drop out of the U.S. Open on Wednesday due to Sjogren's syndrome, an autoimmune disease that causes fatigue and pain.

“I’m not sure what my journey will be, but I feel really positive about getting back on the court and getting to at least get back to normal,” Venus Williams told ABC’s Good Morning America Thursday. “My normal might not be everyone else’s normal, but I feel like now I can get better.”

Symptoms of the condition include swelling, numbness and fatigue. The illness isn't considered life threatening, but may keep the two-time U.S. Open champion away from the court for a conceivable future.

In rare cases, the disease can cause arthritis and joint pain, Dr. John Fitzgerald, director of clinical rheumatology at UCLA told the Associated Press.

Fitzgerald is not involved in treating Williams and does not know her symptoms or medical history, however, he said, if Williams has the common symptoms, it does not seem life-threatening or career-ending.

Williams, who was supposed to play second-round match against Sabine Lisicki, is reportedly nearing the end of her career and the new diagnosis could expedite that process.

I'm really disappointed to have to withdraw from this year's U.S. Open, Williams said in a statement. I have recently been diagnosed with Sjogren's syndrome, an autoimmune disease which is an ongoing medical condition that affects my energy level and causes fatigue and joint pain.

What is Sjögren's Syndrome?

According to the Sjogren's Syndrome Foundation, it is a chronic autoimmune disease in which people's white blood cells attack their moisture-producing glands. Today, as many as four million Americans are living with this disease.

It's an autoimmune disease that is typically characterized by inflammation in the tear ducts and salivary glands. We're not sure why it focuses on these tissues, Dr. Victoria Shanmugam, an assistant professor of rheumatology at Georgetown University, to explain the condition, told TIME.

More than 4,000,000 Americans suffer from Sjögren’s syndrome, which on average, takes nearly seven years to be diagnosed of the syndrome that affects nine out of 10 female patients.

A small proportion of people will go on to have multi-organ system disease that behaves a little more like lupus [another autoimmune disease in which the body's own immune cells start to attack healthy tissues, particularly in the joints], added Shanmugam.

Joint and muscle inflammation and fatigue can also occur, ABC News reports.