Patient presentation: An otherwise healthy 29-year-old white woman presented to our emergency department with leg pain and edema. She was well until 2 weeks before, when she developed lower back pain following a 3-hour flight. Her pain progressed despite treatment with ice packs, nonsteroidal anti-inflammatory drugs, and stretching, and it became so severe that she was unable to sit comfortably at work. Five days before presentation, she began noticing tightness in both thighs and subtle swelling of both legs, as well. Over the subsequent 48 hours, she experienced rapidly worsening bilateral lower extremity swelling, primarily in her thighs, accompanied by pain in her legs. She denied dyspnea, palpitations, chest pain, abdominal distension, or lightheadedness. Her symptoms worsened to the point where ambulation was difficult, thus prompting her visit to the emergency department. Additional medical history was notable for no previous illnesses or surgeries. Medications included ethinyl estradiol and levonorgestrel (a combination oral contraceptive). She had no known drug allergies. She denied tobacco or illicit drug use and consumed alcohol in moderation. There was no family history of venous thromboembolism (VTE), stroke, or sudden death. © 2016 American Heart Association, Inc.