Micro & Immunology · single question
Same patient. Four weeks later, they develop target lesions on skin. What is the diagnosis?
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Correct answer: A. Type IV hypersensitivity reaction
- A. Correct. Target lesions appearing 4 weeks after antigen exposure represent Type IV (delayed, cell-mediated) hypersensitivity. The delayed timing and target lesion morphology distinguish this from the earlier Type I acute reaction.
- B. Incorrect. Type I already occurred acutely. This new delayed presentation is Type IV.
- C. Incorrect. Lichen planus shows Wickham's striae, not target lesions.
- D. Incorrect. Pemphigus shows flaccid bullae with Nikolsky sign, not target lesions.
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