WBR0153

Author	PageAuthor::William J Gibson
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Microbiology, MainCategory::Pathophysiology
Sub Category	SubCategory::Dermatology, SubCategory::General Principles
Prompt	[[Prompt::A mother brings her two-year-old son into your office complaining of irritability, poor appetite and diarrhea for the past two days. He has developed a rash surrounding his mouth (pictured below) and a similar rash on his hands and feet. Which of the following describes the most likely causal organism? ]]
Answer A	AnswerA::Enveloped ssRNA virus with icosahedral capsid symmetry
Answer A Explanation	[[AnswerAExp::Enveloped ssRNA viruses with icosahedral capsid symmetry encompasses several families of RNA viruses including flaviviruses, togavirsuses, and retroviruses. For example, Rubella virus is an enveloped ssRNA virus with icosahedral capsid symmetry. It causes a fine truncal rash and postauricular lymphadenopathy. Rubella virus is not the cause of hand, foot and mouth disease.]]
Answer B	AnswerB::Enveloped dsDNA virus with icosahedral capsid symmetry
Answer B Explanation	[[AnswerBExp::The herpesviridae family is composed of dsDNA viruses, including HSV1 and VZV. HSV1 can cause an vesicular rash near the mouth like the one pictured, but does not cause rash on the hands or feet.]]
Answer C	AnswerC::Nonenveloped dsDNA virus with icosahedral capsid symmetry
Answer C Explanation	AnswerCExp::This describes adenovirus which is responsible for pink eye, not hand foot and mouth disease.
Answer D	AnswerD::Nonenveloped ssRNA virus with Icosahedral capsid symmetry
Answer D Explanation	[[AnswerDExp::Coxsackie A is the etiologic agent of hand foot and mouth disease. It is a picornavirus, which is a nonenveloped, ssRNA virus with icosahedral capsid symmetry.]]
Answer E	AnswerE::Spirochete
Answer E Explanation	[[AnswerEExp::While Syphillus can cause a rash on the hand and feet it does not cause this sort of rash on the mouth and it is much more likely that the child has hand foot and mouth disease.]]
Right Answer	RightAnswer::D
Explanation	[[Explanation::The child in this vignette is affected by hand foot and mouth disease as a result of infection with Coxsackievirus A, an intestinal virus of the picornaviridae family. Hand foot and mouth disease is a contagious disease that usually affects infants and children. Affected individuals experience fever, headache, fatigue, malaise, sore throat, and a characteristic body rash followed by sores with blisters on palms of the hands, soles of the feet and around the mouth. Picornaviridae such as coxsackie are nonenveloped ssRNA viruses with icosahedral capsid symmetry. It is also worth remembering that the closely related Coxsackie B virus causes myocarditis. Educational Objective: Coxsackie A virus causes hand foot and mouth disease. Coxsackie A is a picornavirus which is a nonenveloped, ssRNA virus with icosahedral capsid symmetry. References: First Aid 2014 page 175]]
Approved	Approved::Yes
Keyword	WBRKeyword::Microbiology, WBRKeyword::Virus, WBRKeyword::RNA virus, WBRKeyword::Coxsackie, WBRKeyword::Pediatrics, WBRKeyword::Rash, WBRKeyword::Skin, WBRKeyword::Hand foot and mouth disease
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