WBR0153

Author	[[PageAuthor::William J Gibson (Reviewed by Yazan Daaboul, M.D.)]]
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 2-year-old son into the pediatrician's office for complaints of irritability and poor appetite for the past 3 days. The patient has developed a rash that surrounds his mouth and on his tongue with a similar rash on his hands and feet. Physical examination is remarkable for a temperature of 38.3 °C (101 °F) and a rash shown below. Which of the following organisms is most likely responsible for the patient's condition? ]]
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. Recall that all DNA viruses have icosahedral capsid symmetry (except for smallpox).]]
Answer C	AnswerC::Nonenveloped dsDNA virus with icosahedral capsid symmetry
Answer C Explanation	AnswerCExp::All DNA viruses have icosahedral capsid symmetry (except for smallpox). Nonenveloped dsDNA viruses include adenovirus, papillomavirus, and polyomavirus. Adenovirus 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::Hand, foot, and mouth disease (HFMD) is a viral infection characterized by the presence of a vesicular or a maculopapular rash that surrounds the mouth, in the oral cavity, and on the hands and feet. Patients with HFMD may also have eruptions on their buttocks and the trunk. The disease is caused by Coxsackievirus A virus that belongs to 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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