Review Question - QID 108650

A 2-year-old male is accompanied by his parents to the emergency room following an injury to the child’s leg. He has been in significant pain since he tripped while walking two hours prior. The child has a history of fractures of the tibia and humerus following minimal trauma. His height and weight are in the 30th and 40th percentiles, respectively. On physical exam, the child demonstrates significant swelling and tenderness over the right femur. No bruises or lacerations are noted elsewhere on his body. A notable physical exam finding is shown in Figure A. A radiograph of the right thigh demonstrates a midshaft femur fracture. Which of the following is the most likely cause of this patient’s condition?