A 14-year-old boy is brought to the emergency department by his mother after he develops a sudden rash. He was trying to retrieve a baseball that had rolled under a log when he got stung by something. By the time he told his mom, his body was covered in welts. His mother gave him diphenhydramine, but the patient's face started to swell and he was having a hard time swallowing. The patient's blood pressure is 70/50 mm Hg and heart rate is 120/min. Physical examination shows erythematous, raised plaques over the trunk, extremities, and face. Lung auscultation reveals bilateral expiratory wheezes. The mother is not aware of the child having any similar reaction in the past. Which of the following most likely triggered this patient's condition?

Question

A 14-year-old boy is brought to the emergency department by his mother after he develops a sudden rash.  He was trying to retrieve a baseball that had rolled under a log when he got stung by something.  By the time he told his mom, his body was covered in welts.  His mother gave him diphenhydramine, but the patient's face started to swell and he was having a hard time swallowing.  The patient's blood pressure is 70/50 mm Hg and heart rate is 120/min.  Physical examination shows erythematous, raised plaques over the trunk, extremities, and face.  Lung auscultation reveals bilateral expiratory wheezes.  The mother is not aware of the child having any similar reaction in the past.  Which of the following most likely triggered this patient's condition?

Quizplus · Accepted Answer

Eductional Objective: Type I hypersensitivity reactions are mediated by the interaction of allergen with preexisting IgE bound to basophils and mast cells.  This facilitates cross-linking of the surface IgE molecules that signals the cell to degranulate releasing chemical mediators (eg, histamine, heparin).  These agents are responsible for the immediate signs and symptoms of allergy, from a local wheal and flare to life-threatening anaphylaxis.

A 14-Year-Old Boy Is Brought to the Emergency Department by His