my sister developed red spots on right arm that gradually grew to raised red blotches with blisters and fever. The blotches grew bigger and spread to her chest and stomach and is slightly painful. A day later she felt pain in her right knee and could not straighten her leg. I took her to ER AT A HOSPITAL. while there her right wrist became slightly red and 5 hrs later her wrist grew swollen. Drs there decided to extract fluid from her knee and found it was full of pus and blood. The next morning Drs had sister in surgery to flush the knee and also tested the wrist, found and extracted fluid there. She is now on antibiotics, shots to prevent blood clots, and intravenous hydration. Sister is still in hospital since no clear cause has been found yet. What is it?