Review Question - QID 213668

A 2-year-old boy is brought to the emergency department after developing swelling of his left middle and ring fingers for the past day. The parents noticed that the boy had some redness of both fingers, and the boy had some agitation from pain yesterday. Today, the pain has become excruciating. The patient has no other medical conditions and was born at term after an uncomplicated pregnancy. On exam, the patient’s temperature is 98.3°F (36.8°C), blood pressure is 114/88 mmHg, pulse is 120/min, and respirations are 14/min. On exam, the patient has fusiform swelling of the left middle and ring fingers, with swelling starting to extend into the hand. The fingers are erythematous and warm and exquisitely tender to touch. After a thorough family history and lab testing, the diagnosis is confirmed. Which of the following is the likely mutation that has occurred in this patient’s condition?