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NBME 23 Answers

nbme23/Block 1/Question#25

A 5-year-old boy who is undergoing induction ...

Varicella-zoster virus

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 +19  upvote downvote
submitted by sajaqua1(348),

Critical points for this question: 5 year old boy, immunosuppressed because of chemotherapy, 2 day history of fever, cough, shortness of breath, febrile (101.8 F), respirations 46/min, with cyanosis and generalized vesicular rash. Extensive nodular infiltration.

Of the options listed only measles and VZV give a rash. A rash from measles usually starts rostrally and descends caudally, and is flat and erythematous. By contrast, VZV (chickenpox) presents with generalized rash that quickly transitions from macular to papular then to vesicular.

sympathetikey  Good call. +3  
imnotarobotbut  Also, VZV causes pneumonia (what this patient probably had) and encephalopathy in the immunocompromised. +5  
nwinkelmann  What threw me off was that it didn't mention the synchronicity of the rash. I stupidly took failure to mention to mean that the rash was synchronous, which doesn't fit VZV because chickenpox rash is characterized as a dyssynchronous rash (i.e. all stages of the macule to papule to vesicle to ulceration are seen at the same time). MUST REMEMBER: don't add information not given! +1  
jboud86  If anyone wants to refresh info on Vaicella-Zoster virus, page 165 in FA 2019. +1  

Per multiple sources: measles can be vesicular and also can lead to giant cell pneumonia in the immunocompromised. ?!?!?!?

 -1  upvote downvote
submitted by seagull(724),

Did anyone think that influenza was right? I understand that Herpes-Z can cause pneumonia but why is this answer better over influenza?

jrod77  I believe it's the vesicular rash that gives it away. I thought it was influenza too, but i re-read the questions and I realized they included a rash which disqualifies influenza. +2  
charcot_bouchard  Also h/o of immunsupression, disseminated VZV. Influenza itself doesnt cause severe disease. secondary PNA does. which u will see in elderly. usually +1