🏥 USMLE Exam Prep

A patient develops a severe systemic reaction with bronchospasm, laryngeal edema, and hypotension minutes after receiving an antibiotic injection. This reaction is mediated primarily by IgE antibodies and mast cell degranulation. What type of hypersensitivity reaction is this?

A Type I hypersensitivity
B Type II hypersensitivity
C Type III hypersensitivity
D Type IV hypersensitivity

✓ Correct Answer: Option A

Type I hypersensitivity (anaphylactic reaction) is an immediate reaction mediated by IgE antibodies, which trigger mast cell and basophil degranulation, releasing histamine and other mediators. This leads to symptoms like bronchospasm and hypotension.

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