A 25-year-old woman is being evaluated for chronic fatigue. She has a history of heavy menstrual periods since menarche and also recalls frequent nosebleeds as a child. Her past medical history is otherwise insignificant and she takes no medications. Laboratory studies show normal prothrombin time (PT), activated paial thromboplastin time (APTT), platelet count and fibrinogen levels. Which of the following is the most likely diagnosis?