Fogo, Ch. 17 - Monoclonal immunoglobulin deposition

Question 1

What is depositing in monoclonal immunoglobulin deposition disease?

Answer 1

Intact monoclonal protein, either light+heavy or light/heavy chains alone.

Question 2

How do monoclonal immunoglobulin depositions clinically present?

Answer 2

Heavy proteinuria, renal insufficiency, hypertension. Half will have overt myeloma.

Question 3

Describe the LM findings in light chain deposition disease (LCDD).

Answer 3

Nodular glomerular lesions and capillary microaneurysms (similar to DN). Thickened BM with outer light-PAS-staining band.

Question 4

Describe the LM findings in heavy chain deposition disease (HCDD)

Answer 4

More frequently nodular than in LCDD. Can be hypercellular/proliferative.

Question 5

Describe the IF findings in LCDD.

Answer 5

Tubular and glomerular basement membrane staining for usually kappa. Can also be in PTC or vascular smooth muscle.

Question 6

Describe the IF findings in HCDD.

Answer 6

Like LCDD (kappa/lambda basement membrane staining), but also with complement deposition if IgG3.

Question 7

Describe the EM findings in monoclonal immunoglobulin deposition diseases.

Answer 7

Clustered punctate dense desposits external to tubular and within vascular basement membranes. Fewer deposits in mesangium.

Question 8

What determines if a monoclonal gammopathy results in AL-amyloidosis or LCDD?

Answer 8

Some intrinsic property of the abnormal light chains, yet to be determined.

Question 9

What parts of the nephron are affected in LCDD?

How many are kappa-related?

Answer 9

All renal basement membranes + mesangium.

80% have abnormal kappa.

Question 10

What immunoglobulin is involved in HCDD?

Answer 10

Usually IgG (recall: If IgG3, hypocomplementemia may result).