WBR0703

Author	[[PageAuthor::Mohamed Moubarak, M.D. [1]]]
Exam Type	USMLE Step 3
Main Category	Emergency Room
Sub Category	Infectious Disease
Prompt	19 year old boy present to the ER with generalized rash, he had fever and sore throat one week ago and got antibiotic prescription from his primary care physician 4 days ago. His past medical history is insignificant. He doesn’t smoke or consume recreational drugs or alcohol. He is sexually active with one partner and uses condoms regularly. Vital signs are normal except for temperature of 37.8 C(100 F). His physical examination reveals generalized maculopapular rash and posterior cervical lymphadenopathy. What is the most likely mechanism of rash development in that patient?
Answer A	Familial
Answer A Explanation	Incorrect Rash to ampicillin doesn’t represent familial predisposition
Answer B	Viral exanthema
Answer B Explanation	Incorrect Viral exanthema usually observed during active viral infections
Answer C	Immediate hypersensitivity
Answer C Explanation	Incorrect The rash doesn’t represent immediate hypersensitivity to ampicilline
Answer D	Delayed hypersensitivity
Answer D Explanation	Incorrect The rash doesn’t represent delayed hypersensitivity to ampicilline
Answer E	Immune complexes
Answer E Explanation	Correct Circulating IgG and IgM antibodies targeting penicillin derivatives is the cause of the well known ampicilline-associated maculopapular rash phenomenon in patients with infectious mononucleosis
Right Answer	E
Explanation	Ampicilline-associated maculopapular rash in patients with infectious mononucleosis is a well know phenomenon. It is caused by the circulating IgG and IgM targeting penicillin derivatives causing this immune vasculitic rash Educational Objective: References:
Approved	No
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