WBR265

Author	[[PageAuthor::Ogheneochuko Ajari, MB.BS, MS [1] (Reviewed by Will Gibson and Yazan Daaboul, M.D.)]]
Exam Type	USMLE Step 1
Main Category	Microbiology
Sub Category	Pulmonology, Infectious Disease
Prompt	A 4-year old boy is brought to the emergency department by his mother with complaints of fever, cough, runny nose, and a rash. The mother reports that the rash began on the forehead and progressively moved downwards. The patient's past medical history is unremarkable. Physical examination is remarkable for post-auricular lymphadenopathy. Which of the following is the most likely pathogen responsible for this patient's symptoms?
Answer A	HHV-6
Answer A Explanation	HHV-6 causes Roseola, a macular rash over the body that appears several days after a high-grade fever.
Answer B	Varicella zoster virus
Answer B Explanation	Varicella zoster virus (VZV) causes chicken pox, in which the rash typically begins from the trunk and then spreads to the face and extremities.
Answer C	Mumps virus
Answer C Explanation	Mumps virus causes mumps, which typically presents with no rash but with parotitis and/or meningitis (pancreatitis, orchitis/oophoritis in young adults).
Answer D	Rubella virus
Answer D Explanation	Infection with the Rubella virus is associated with the development of a descending rash and post-auricular lymphadenopathy.
Answer E	Measles virus
Answer E Explanation	Measles virus causes measles. The rash in measles is preceded by cough, coryza, conjunctivitis and blue-white (Koplik) spots on the buccal mucosa.
Right Answer	D
Explanation	The patient is most likely diagnosed with Rubella virus infection (German measles). The primary symptom of rubella virus infection is the appearance of a rash (exanthem) on the face which spreads to the trunk and limbs and usually fades after three days. Other symptoms include low grade fever, swollen glands (typically post-cervical/post-auricular lymphadenopathy), joint pains, headache, and conjunctivitis. The swollen glands or lymph nodes can persist for up to a week, and the fever rarely rises above 38 oC (100.4 oF). The rash disappears after a few days with no staining or peeling of the skin. Educational Objective: Rubella virus causes German measles with the clinical presentation of post-auricular lymphadenopathy and rash. References: First Aid 2015 page 163
Approved	Yes
Keyword	Microbiology, Virus, Viruses, Rubella, Rash, Skin, Togavirus
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