A 15-year-old boy with confirmed Epstein-Barr virus infectious mononucleosis is given ampicillin for a presumed streptococcal infection. He develops a diffuse maculopapular rash. What is the mechanism of this rash?
- A IgE-mediated hypersensitivity
- B Immune complex-mediated reaction ✓
- C Cytotoxic antibody reaction
- D Delayed-type hypersensitivity
Correct answer: B. Immune complex-mediated reaction
Explanation
The ampicillin rash in EBV infection is a benign, non-allergic maculopapular eruption caused by immune complex formation, not a true drug allergy. It occurs in over 90% of patients with EBV infection given ampicillin. IgE-mediated hypersensitivity would cause urticaria or anaphylaxis. Cytotoxic and delayed-type reactions are not typical in this setting.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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