Case 21: Pathology

Case 21 Index

Excellent work, your patient tolerated the kidney biopsy well. Let’s take a look at the stain below.  Click here for some quick pathology tips.

Light Chain Cast with Cellular Reaction.jpg

First things first. What type of stain do you see above?
Hematoxylin & Eosin (H&E) stain
In the stain above, we see a deep pinkish/magenta staining of collagen and the tubular basement membrane. We would not see that with and H&E stain. Try again!
Periodic Acid-Schiff (PAS) stain
Correct! The PAS stain allows us to visualize collagen structures better by staining it a deep pink/magenta color as seen here in the tubular basement membrane.
Silver stain
Though the silver stain does stain for collagen, we would see this as a black color rather than a pink/magenta. Try again!
Positive immunohistochemistry (IHC) stain
IHC stains look for a specific antigen and stain this antigen a brown color. We don’t see that here.
Masson’s trichrome stain
The trichrome stain is used to look for fibrosis – which typically stains a bright blue color. Try again!

A couple of days later, the immunofluorescence (IF) stains are ready for you. Here they are below (Kappa staining on the right, lambda staining on the left) :

Given the pathology findings above, which of the following is the next best test to confirm this diagnosis?
Serum protein electrophoresis (SPEP) and immunofixation
Nailed it! The SPEP reveals a monoclonal spike in the gamma zone, and the immunofixation confirms that the protein is IgG. The serum and urine free light chains will provide us with information
Immunoglobulin levels
Though this test result may be abnormal, it is not the highest yield test to confirm the diagnosis in this case.
Hepatitis C antibody
The finding above would not be caused by Hepatitis C infection. HCV-associated GN often presents with a membranoproliferative GN pattern.
Hepatitis B antibody
The finding above would not be caused by Hepatitis B infection. HBV-associated GN often presents with a membranous nephropathy pattern
Parvovirus serum PCR
Parvovirus is associated with focal segmental glomerulosclerosis (FSGS), which we don’t see here.
Vancomycin random level
Vancomycin can cause acute tubular necrosis. Though we do see tubular injury, vancomycin toxicity would not explain the main finding above.

Click here once you are confident in your final diagnosis!

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Case 21 Introduction
Case 21 Physical Exam
Case 21 Diagnostic Testing