What Do Pain And Swelling In The Joints Along With Fatigue Indicate?

20 year old female, my daughter college student, developed rapid onset of painful, red joint swelling, fatigue, pain with mobility, low grade fever, severe itching over entire body. Had c/o headache before rated 5/10. Had been on Macrobid for a UTI and had no reaction during the course of tx. Hx. of Hoshimoto s thyroid. On birth control pill. Some type of bug bite on knee but this was after headache. Runs and walks and general healthy has had episode of hypotension in the past. Went to ER. Prednisone 40mg qd, Augmentin x 10 days, CBC, CMP, CRP, thyroid normal. What is this? They didn t know.