American Olympians With Health Scares

In September 2011, Venus Williams (right) was diagnosed with Sjogren's syndrome, an autoimmune disease, just six months after her younger sister Serena Williams was rushed to a Los Angeles hospital for complications from a blood clot in her lung. Now the tennis star siblings, 32 and 30, are back in the game, landing a spot in the pairs semi-finals Friday. Serena made the semis for singles, too. (Paul Gilham/Getty Images)