WBR0295

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Author [[PageAuthor::Ogheneochuko Ajari, MB.BS, MS [1]]]
Exam Type ExamType::USMLE Step 1
Main Category MainCategory::Pathophysiology
Sub Category SubCategory::Dermatology
Prompt [[Prompt::A 42-year-old male presents to the ER with a fever, chills, and facial pain, which had began three days prior. Upon further questioning, he states that he accidentally cut his face while shaving. Physical examination reveals a very red and swollen skin lesion with blisters and a raised border that is warm to touch on the left side of the face. Which of the following mechanisms is true about the lesion?]]
Answer A AnswerA::The redness and warmth is due to histamine-mediated vasoconstriction of arterioles
Answer A Explanation AnswerAExp::Incorrect. The redness and warmth is due to histamine-mediated vasodilation of arterioles and not due to vasoconstriction of arterioles
Answer B AnswerB::The redness and warmth is due to histamine-mediated vasodilation of venules
Answer B Explanation AnswerBExp::Incorrect. The redness and warmth is due to histamine-mediated vasodilation of arterioles and not due to vasodilation of venules
Answer C AnswerC::The redness and warmth is due to histamine-mediated vasodilation of arterioles
Answer C Explanation AnswerCExp::Correct. See explanation
Answer D AnswerD::The swelling is due to histamine mediated decrease in permeability of venules
Answer D Explanation AnswerDExp::Incorrect. The swelling is due to histamine mediated increase and not a decrease in permeability of venules
Answer E AnswerE::The pain is caused by PGE2 sensitization of specialized nerve endings to the effects of serotonin
Answer E Explanation AnswerEExp::Incorrect. The pain is caused by PGE2 sensitization of specialized nerve endings to the effects of bradykinin
Right Answer RightAnswer::C
Explanation [[Explanation::This is a case of Erysipelas of the face due to group A streptococcus. Signs of acute inflammation present in this patient include Rubor (redness), Calor (warm to touch), Tumor (swelling) and Dolor (pain). The infection is associated with a warm skin (calor) and pain (dolor). The redness and warmth experienced by this patient is due to histamine-mediated vasodilation of arterioles

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