USMLE® Step 1 style questions USMLE
A 4-year-old girl is brought to the pediatrician's office by her grandmother because of multiple ecchymotic patches over both shoulders. Her medical history is relevant for multiple hospital admissions when she was born. Physical exam shows swollen gums, poor dental hygiene, and a petechial rash over her face. Her temperature is 36.4°C ( 97.52°F), pulse is 101/min, respirations are 17/min, blood pressure is 120/70 mmHg. Laboratory studies show prolonged bleeding time, but platelet count and coagulation tests are normal. Which of the following is the most likely cause of this patient's condition?