A 17-year-old girl presents with a four-day history of fever, malaise, and migratory joint pain involving the right knee, right ankle, right elbow, and left knee in turn. The affected joints were tender and swollen, but not erythematous. There was no morning stiffness. She had a sore throat two weeks ago, which resolved spontaneously. Her medical, surgical, family, and drug histories are unremarkable. She is not on any medications, including over-the-counter medicines or supplements. She has no known allergies. All vaccinations are up-to-date. She denies recreational drug use. She is currently single but is sexually active. Her last episode of intercourse was around one month ago.