WBR0295

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::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::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::See explanation
Answer D	AnswerD::The swelling is due to histamine mediated decrease in permeability of venules
Answer D Explanation	AnswerDExp::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::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 Educational Objective: The tissue redness of Erysipelas is caused by histamine-mediated vasodilation of aterioles. References: First Aid 2014 page 244]]
Approved	Approved::Yes
Keyword	WBRKeyword::Histamine, WBRKeyword::Infection, WBRKeyword::Rubor, WBRKeyword::Rash
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::