A 16-year-old girl is brought to the physician for recurrent episodes of shortness of breath, nonproductive cough, and chest tightness for 3 months. These episodes occur especially while playing sports and resolve spontaneously with rest. She appears healthy. Her pulse is 63/min, respirations are 15/min, and blood pressure is 102/70 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 98%. Physical examination shows no abnormalities. An x-ray of the chest shows no abnormalities. Skin testing is performed to determine symptom triggers. A pricking device is used to apply allergen extract underneath the skin. After 15 minutes, the patient develops raised, erythematous plaques with surrounding erythema at the application site. Which of the following mediators is the first to be released during the pathogenesis of this patient's skin findings?

Question

A 16-year-old girl is brought to the physician for recurrent episodes of shortness of breath, nonproductive cough, and chest tightness for 3 months. These episodes occur especially while playing sports and resolve spontaneously with rest. She appears healthy. Her pulse is 63/min, respirations are 15/min, and blood pressure is 102/70 mm Hg. Pulse oximetry on room air shows an oxygen saturation of 98%. Physical examination shows no abnormalities. An x-ray of the chest shows no abnormalities. Skin testing is performed to determine symptom triggers.  A pricking device is used to apply allergen extract underneath the skin.  After 15 minutes, the patient develops raised, erythematous plaques with surrounding erythema at the application site.  Which of the following mediators is the first to be released during the pathogenesis of this patient's skin findings?

Quizplus · Accepted Answer

Eductional Objective: Type I hypersensitivity reactions are an allergic response triggered by the binding of previously recognized antigen to IgE antibodies on mast cells.  In the early phase of the response, histamine, already stored in preformed granules in mast cells, is the first chemical mediator released.  Once released, histamine stimulates smooth muscle contraction (bronchoconstriction), increases vascular permeability (edema), and increases mucus secretion.

A 16-Year-Old Girl Is Brought to the Physician for Recurrent