Gynecologic — Abnormal vaginal bleeding

A 13-year-old girl is brought to the emergency department by her mother because of 8 days of heavy vaginal bleeding. Menarche was at age 12, and her periods since have lasted 7 to 10 days with clots. Today she has been soaking a pad every 1 to 2 hours and feels dizzy when she stands. She has frequent nosebleeds, and her mother needed iron infusions for heavy periods. She takes no medications and has no personal or family history of thrombosis. When interviewed alone, she states she has never been sexually active. She looks pale, and her abdomen is soft and non-tender.