USMLE® Step 1 style questions USMLE
A 14-year-old girl comes to the pediatrician's office because of recurrent nose bleeding. Her medical history is relevant for heavy menstrual bleeding and easy bruising. Upon further interrogation, the patient mentions that she always bleeds when she brushes her teeth. Physical exam shows purple discolored spots on her right leg that do not blanch on applying pressure and petechial rash over her face. Her temperature is 36.8°C (98.2°F), pulse is 106/min, respirations are 16/min, blood pressure is 90/70 mmHg. Laboratory studies show moderate thrombocytopenia and prolonged bleeding time. A peripheral blood smear is obtained and shows the presence of multiple large platelets.
Which of the following abnormalities is the most likely cause of these findings?