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NBME 24 Answers

nbme24/Block 1/Question#13

A 4-year-old boy is brought to the emergency ...

Proliferative glomerulonephritis

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Directly from wikipedia:

"Acute proliferative glomerulonephritis is a disorder of the glomeruli (glomerulonephritis), or small blood vessels in the kidneys. It is a common complication of bacterial infections, typically skin infection by Streptococcus bacteria types 12, 4 and 1 (impetigo) but also after streptococcal pharyngitis, for which it is also known as postinfectious or poststreptococcal glomerulonephritis."

 +2  upvote downvote
submitted by usmile1(34),

Membranous nephropathy and minimal change disease can be easily ruled out as they are nephrotic syndromes. Tubulointerstitial nephritis (aka acute interstitial nephritis) can be ruled out as it causes WBC casts not RBC as seen in this question. Papillary necrosis - either has no casts or it might show WBC casts but not RBC because the problem is not in the glomeruli.

table of nomenclature on page 582 explains that proliferative just means hyper cellular glomeruli. Given the patients history of sore throat two weeks ago, now presenting with Nephritic Syndrome with RBC casts, proliferative glomerulonephritis is the only reasonable answer.

medguru2295  This was my precise login. I wound up getting it by elimination. But, didn't like that answer as its uncommon in small children and the child seemingly had no risk factors. +  
thotcandy  @medguru2295 FA says it's most commonly seen in children and it's selflimited vs adults is rare and can lead to renal insuff +  

 +1  upvote downvote
submitted by mousie(129),

is this subacute endocarditis associated Membrano-proliferative GN?

jus2234  The question describes how he had a strep infection 15 days ago, and now this is poststreptococcal glomeruloneprhitis, which can also be described as proliferative glomerulonephritis +8  
seagull  The question would be too fair if it just said PSGN. Instead we need to smell our own farts first. +42  
yotsubato  And they used terminology NOT found in FA +5  
water  who said they were limited to FA? +2  
nbmehelp  FA uses the common nomenclature and the fact most of our other resources use the same nomenclature for this, I think we can agree that is is the accepted terms. If they're gonna decide not to use the nomenclature that most medical students are taught then they should provide their own study materials at that point for us to use. The test shouldn't be this convoluted for no reason. +3  

 +1  upvote downvote
submitted by nbmehelp(17),

This is BS bc PSGN is like the only nephrotic/nephritic syndrome I thought I had down cold

 +0  upvote downvote
submitted by ap88(0),

Why can this not be papillary necrosis? Given the gross Hematuria and proteinuria with a history of analgesic use... I thought that was what this was getting at?

biaancadb  I was confused about this too. Only thing I had to go on is that I wrote down from somewhere that you see papillary necrosis in middle-aged adults and that it's uncommon in children (except those with sickle cell). Also I'm assuming PSGN is technically a proliferative glomerulonephritis since on FA pg. 578 the definition of proliferative is "hypercellular glomeruli", and for PSGN, you see hypercellular glomeruli on LM (due to leukocyte infiltration). +1  
gubernaculum  also papillary necrosis tends to be the cause of these 4 (SAAD papa): Sickle cell, Acute pyelonephritis, Analgesics, Diabetes, which the patient does not have +  

 +0  upvote downvote
submitted by diabetes(11),

RBC casts===> glomerulonephritis the only option there.

thotcandy  I saw BUN/cr > 20 and instantly though prerenal --> ischemic pap necrosis due to analgesics. Are nephritic syndromes just excluded from that whole thing? FA says BUN and Cr are increased for nephritic syndromes but does the ratio just not matter? +  

 -4  upvote downvote
submitted by nwinkelmann(198),

So actually.... Medscape says that PSGN can progressive to a proliferative glomerulonephritis mechanism and so proliferative glomerulonephritis should be considered as a differential diagnosis for PSGN.

https://emedicine.medscape.com/article/980685-overview#a5: "The presence of acute kidney injury may suggest an alternate diagnosis (eg, membranoproliferative glomerulonephritis [MPGN], Henoch-Schönlein purpura [HSP], systemic lupus erythematosus [SLE]) or a severe or worsening APSGN, such as observed in those with crescentic glomerulonephritis or rapidly progressive glomerulonephritis... Differential Diagnosis: This includes most other types of childhood glomerulonephritides. These include IgA nephropathy, membranoproliferative glomerulonephritis, hereditary nephritis, and other forms of postinfectious glomerulonephritis."

Ironically enough, this must be what they were asking, i.e. complications of PSGN, because AMBOSS (another Step resource) directly linked the above article I found before looking farther and coming across the AMBOSS section.