New York: American tennis star Venus Williams has revealed that she has been diagnosed with Sjogren`s syndrome - an autoimmune disease that has no known cure.
Williams pulled out of her second-round match at the US Open less than an hour before she was due to play Sabine Lisicki at New York`s Arthur Ashe Stadium on Wednesday.
She later explained in a statement that Sjogren`s syndrome is "an ongoing medical condition that affects my energy level and causes fatigue and joint pain."
"I am thankful I finally have a diagnosis and am now focused on getting better and returning to the court soon," it added.
Williams has been dogged by injury and illness lately. Her problems included a bad hip and a torn abdominal muscle, but she was also reported to have a persistent illness, media reports.
Sjogren`s syndrome is a systemic autoimmune disease in which immune cells attack and destroy the exocrine glands that produce tears and saliva.
It is named after Swedish ophthalmologist Henrik Sjogren (1899-1986), who first described it.
Nine out of ten Sjogren`s patients are women and the average age of onset is late 40s, although Sjogren`s occurs in all age groups in both women and men.
It is estimated to strike as many as four million people in the US alone making it the second most common autoimmune rheumatic disease.
Sjogren`s syndrome can exist as a disorder in its own right or it may develop years after the onset of an associated rheumatic disorder such as rheumatoid arthritis, systemic lupus erythematosus, scleroderma and primary biliary cirrhosis.