Fogo, Ch. 16 - Bence Jones cast nephropathy

Question 1

How does BJ cast nephropathy clinically present?

Answer 1

AKI and BJ proteinuria.

Question 2

What causes precipitation of BJ proteins into casts?

Answer 2

Usually a trigger like contrast, dehydration, infection, or NSAID use. Rarely acquired fanconi syndrome (note plasma cell and tubular intracytoplasmic crystal inclusions)

Question 3

Describe the LM appearance of BJ casts.

Answer 3

Large, eosinophilic and “brittle” casts. Can be lamellated. Staining is variable but usually PAS-, congo-.

Question 4

Describe the tubular LM findings in BJ nephropathy.

Answer 4

Proximal tubular cells have numerous cytoplasmic vacuoles. Can have tubular necrosis with discontinuous basement membranes.

Question 5

Describe the interstitial findings in BJ nephropathy.

Answer 5

Interstitial monocytic inflammation. Giant cells react to the crystals which can leak into the interstitium.

Question 6

What are the IF findings in BJ nephropathy?

Answer 6

Strong kappa or lambda staining. Can have other plasma proteins too (less intense).

Question 7

What are the EM findings in BJ nephropathy?

Answer 7

Casts are deeply electron dense. They can be homogeneous or incorporate cytoplasmic debris.

Question 8

Describe the pathogenesis of BJ nephropathy.

Answer 8

Light chain is freely filtered and is somehow toxic to tubular cells. Tubular necrosis can result.

Question 9

Where do casts usually appear? What are they composed of?

Answer 9

Usually in distal tubule (coprecipitate with THP), but can be proximal (solo).

Question 10

Why are light chains toxic to tubular cells?

Answer 10

Unknown