Veteran American tennis star Venus Williams has quit the US Open, saying she is suffering from a chronic illness that could threaten her future in the sport.
The two-time US Open champion withdrew less than an hour before she was due to play Germany's Sabine Lisicki in the second round in New York on Wednesday.
Williams issued a statement explaining that she has recently been diagnosed with Sjogren's Syndrome, an energy-draining auto-immune disease.
Nine out of 10 patients are women and most experience extreme fatigue and joint pain, Reuters reports.
Williams has been battling health problems for the past year. She retired from her third-round match at the Australian Open with a hip problem and did not play again until June.
The 31-year-old played only a handful of matches since making her comeback and had not played since Wimbledon, pulling out of recent tournaments in Toronto and Cincinnati.
Williams, whose achievements have been largely overshadowed by her sister Serena's, has not won a grand slam title since 2008, but says she has no thoughts of retiring.