Review Question - QID 109746

A 4-year-old boy is brought by his mother to the emergency room after the child was bitten by a rattlesnake one hour prior to presentation. The child was reportedly playing in the backyard alone when his mother heard the child scream. She rushed out to her child and found a snake with a rattle on its tail slithering away from the child. On examination, the child has a bleeding bite mark and significant swelling over the dorsal aspect of his right hand. He is in visible distress and appears pale and diaphoretic. The child undergoes fluid resuscitation and is placed on supplemental oxygen. He is administered rattlesnake antivenom and is admitted for observation. He is subsequently discharged 24 hours later feeling better. However, 6 days after admission, he presents again to the emergency department with a temperature of 102°F (38.9°C), diffuse wheals, and knee and hip pain. This patient’s condition is caused by which of the following?