NBME 21 Membranous glomerulonephritis (NBME Answers)

Retired NBME 21 Answers

nbme21/Block 3/Question#34 (reveal difficulty score)
A 39-year-old woman with rheumatoid arthritis ...
Membranous glomerulonephritis 🔍 / 📺 / 🌳 / 📖
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submitted by ∗mcl(671)

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Membranous glomerulopephritis (aka membranous nephropathy, p 584 FA 2019) may occur secondary to drugs such as penicillamine. Immunofluorescence shows granular deposits due to immune complex deposition. Will also see diffuse capillary and GBM thickening, and SEM will show spike and dome appearance due to subepithelial deposits.

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submitted by deannosancuck(6)

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Membranous Glomerulonephritis is Nephrotic; ONLY PROTEINURIA is in the vignette

It can't be MPGN because MPGN is Nephritic with possible Nephrotic

Other choices are eliminated by Renal Biopsy

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hungrybox agreed "granular deposits" rules out MCD (the only other nephrotic syndrome) because MCD is IF (-) +4

cooldudeboy1 could someone explain why the other choices are ruled out by biopsy? +

arlenieeweenie @cooldudeboy1 PSGN does have a granular immunofluorescence, but there is no previous illness or hematuria mentioned so you can rule that out. Goodpasture is classically linear IF since they're antibodies against the GBM. IgA nephropathy is mesangial IF so it would deposit more in the middle. Minimal change wouldn't show anything on IF +3

qball I know First Aid states MPGN as a nephritic disease but I think it can present as nephritic or nephrotic syndrome. https://emedicine.medscape.com/article/240056-clinical. Of course, the renal biopsy helps give it away but I wouldn't be so quick as to rule out MPGN +1

taediggity Totally agree w/ you Qball... I thought MPGN too, but I think Penicillamine makes it Membranous Nephropathy +

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submitted by stefanmil(2)

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Why we have deposits in the glomerular membrane. It supposed to be subepithelial - spike and dome - granulations, right?

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lovebug @stefanmil Yap. you're right. I think "Spike and dome" @ EM. and Diffuse capillary and GBM thickening in @ LM. +1

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submitted by ∗sahusema(173)

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It sounds a lot like PSGN, but PSGN is nephritic and we would see pronounced hematuria with minimal proteinuria.

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