9/22- Cases Membranous, Crescentic, Post-infectious and Membranoproliferative GN Flashcards

1
Q

Into what 3 categories can renal diseases be divided?

A

Diseases affecting:

  • Glomeruli
  • Tubulo-interstitium
  • Vessels
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2
Q

Clinical presentations of:

  • Nephrotic syndrome
  • Nephritic syndrome
  • Acute renal failure
  • Chronic renal failure
A

Nephrotic syndrome

  • Proteinuria, edema, hypoalbuminemia, hypercholesterolemia, lipiduria

Nephritic syndrome

  • Hematuria, mild proteinuria, hypertension

Acute renal failure

  • Oliguria or anuria, elevated BUN and creatinine

Chronic renal failure

  • Chronic elevation of BUN and Creatinine
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3
Q

Case)

  • A 56 year-old woman without any significant past medical history presented with progressive edema for the past two months
  • An annual check-up 10 months ago showed no protein excretion and normal serum creatinine (0.7mg/dl)
  • Currently, the serum creatinine was 1.1 mg/dl.
  • There was 4+ proteinuria by dip stick and the 24-hour urine collection revealed 5 grams of protein.
  • Urine analysis showed 5 RBCs and no WBCs/HPF.
  • All serologic studies including ANA, anti-DNA, and viral hepatitis panel were negative.
  • A renal biopsy was performed.

What renal syndrome does this pt have?

Why is a renal biopsy indicated?

A

NEPHROTIC syndrome.

The two most important elements of this syndrome:

  • Proteinuria > 3 g/day
  • Peripheral edema

(Other elements include: hypeprlipidemia, lipiduria, hypoalbuminemia; plasma albumin under 3 g/dL)

There are a variety of renal lesions that can cause nephrotic syndrome and a specific diagnosis is needed for proper management of this patient.

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4
Q

Protein loss implies disease at what level?

A

Glomerulus

  • Abnormal filtration and excretion of proteins
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5
Q

What provides the negative charge on the glomerular filtration membrane?

A
  • Heparan sulfate -> GBM (-)
  • Sialoproteins -> podocyte/endothelium (-)
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6
Q

What are possible causes of nephrotic syndrome?

A

Many; limited number account for a majority

Pediatrics:

  • Minimal change disease (#1 in kids)
  • Focal segmental glomerulosclerosis (idiopathic)

Adults:

  • Membranous glomerulonephropathy
  • Focal segmental glomerulosclerosis (idiopathic)
  • Diabetic nephropathy
  • Amyloidosis
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7
Q

What is seen here?

A

Membranous glomerulopathy (inset = normal)

  • Diffuse thickening of the glomerular capillaries
  • Glomerular capillary loops appear thickened, eosinophilic and “stiff
  • Some capillary loops may actually appear “fuzzy” and special stains may shows a “spiked” GBM or “hair on end” appearance
  • Epi- or intramembranous deposits (red dots) may be seen on Trichrome staining
  • It is not uncommon to have increased mesangial matrix and even segmental lesions
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8
Q

What does the IF staining for IgG show in Membranous GN?

A

Global, diffuse, and granular staining for IgG along the glomerular capillaries

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9
Q

What do you see in the EM of membranous GN?

A
  • Multiple subepithelial or intramembranous immune deposits
  • Thickened basement membrane
  • Effacement of foot processes

(Don’t confuse with “humps”; latter are more like haystacks)

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10
Q

What will show up on silver stain in membranous GN?

A

EM with subepithelial electron dense deposits, separated by spikes of basement membrane material.

  • Silver stains basement membrane but not deposits
  • Results in “hair on end”, spiked look
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11
Q

What are the different types of Membranous GN?

A

Primary: idiopathic

Secondary:

  • Solid tumors*
  • Systemic lupus
  • HepB
  • Some drugs

*Up to about 5-10% of cases of membranous glomerulonephropathy (esp in elderly) are associated with neoplasms

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12
Q

Treatment: membranous GN?

A
  • Investigate for 2ndary causes
  • then start on steroid therapy?
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13
Q

Case 2)

  • A 62 year-old woman without a significant past medical history presented with sore throat, malaise, arthralgia, and weight loss
  • Physical examination was unremarkable.

Lab findings:

  • Serum creatinine 3.6 mg/dl
  • Urine analysis 3+ blood, 1+ protein + P-ANCA 1:600; + MPO-ANCA 20U/dl; negative C-ANCA, ANA, anti-DNA antibody, anti-GBM antibody, hepatitis serology, rheumatoid factor; normal serum C3 and C4.
  • A renal biopsy was performed.

What renal syndrome does this patient have?

Why was a renal biopsy performed in this patient?

A

NEPHRITIC syndrome

  • Decreased renal function
  • Hematuria (RBCs in urine)
  • Classically: grossly visible hematuria, mild-mod proteinuria and HTN

Why renal biopsy?

  • Possibility of a glomerulonephritis
  • The positive ANCA suggests that the glomerulonephritis may be related to ANCA.
  • However, there is still reason to perform the kidney biopsy in this patient
  • ANCA may be positive in many unrelated conditions including inflammatory bowel disease, some types of hepatitis, and other non-renal immune-mediated diseases
  • In addition, there are well-illustrated cases in which there is a discrepancy between the clinical presentations and the renal lesions revealed by kidney biopsy
  • Therefore, the kidney biopsy findings serve not only to confirm the diagnosis of crescentic glomerulonephritis but also to determine how severe and how active the renal lesions are.
  • These features are important for treatment decisions.
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14
Q

What is the underlying pathophysiology of nephritic syndrome?

A

Disruption of capillary loops with spillage of protein and red cells

  • Active urinary sediment Spilled proteins may incite crescent formation
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15
Q

What is the significance of the laboratory findings, especially the serologic tests?

  • Serum creatinine 3.6 mg/dl
  • Urine analysis 3+ blood, 1+ protein

+ P-ANCA 1:600; + MPO-ANCA 20U/dl; negative C-ANCA, ANA, anti-DNA antibody, anti-GBM antibody, hepatitis serology, rheumatoid factor; normal serum C3 and C4.

A

Help with DDx for crescentic glomerulonephritis

  • Negative ANA, anti-DNA, and anti-GBM and other negative serological tests help to rule out lupus nephritis, anti-GBM antibody mediated disease and viral hepatitis-related glomerular lesions
  • Positive ANCA supports possibility of ANCA-related glomerulonephritis
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16
Q

What is ANCA?

A

AntiNeutrophilic Cytoplasmic Antibodies

  • Mainly in primary granules of neutrohpils, but also lysosymes of monocytes and endothelial cells
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17
Q

What are the 2 ANCA patterns?

A

Cytoplasmic (C-ANCA)

  • Proteinase 3 (PR-3)
  • Lysosomes of neutrophils and monocytes
  • Rule in neutrophil maturation
  • Digest tissues to facilitate neutrophil migration to inflammatory sites Perinuclear (P-ANCA)
  • Myeloperoxidase (MPO)
  • In lysosomes of neutrophil and monocytes
  • Helps generate reactive oxygen mcls that are bactericidal

THINK: C3PO

18
Q

How is ANCA detected?

A

Immunofluorescent (IF) technique

  • Normal human alcohol fixed neutrophils as substrate
  • Cytoplasmic pattern (C-ANCA)
  • Perinuclear pattern (p-ANCA): artifactual due to redistribution of the MPO to perinuclear location during alcohol fixation

Enzyme linked immunosorbent assay (ELISA)

  • C-ANCA PR3-ANCA
  • P-ANCA MPO-ANCA
19
Q

What does biopsy show?

A

Crescentic glomerulonephritis

  • Circumferential cellular crescent (outlined) compressing the underlying glomerular caps
  • Collapsed glomerular tufts with a crescent shaped mass of proliferating cells and leukocytes internal to Bowman capsule
  • The crescents are formed by proliferation of parietal epithelial cells and by migration of monocytes and macrophages into Bowman’s space
  • Neutrophils and lymphocytes may be present.
  • The crescents eventually obliterate Bowman’s space and compress the glomerular tuft
  • Fibrin strands are present between the cellular layers in the crescents.
20
Q

What is seen here?

A

Crescentic glomerulonephritis

  • A cellular crescent with focal rupture of Bowman’s capsule (arrow) with surrounding inflammation
  • Intact Bowman’s capsule (arrow head).
21
Q

What is seen here?

A

Crescentic glomerulonephritis

  • Cellular crescent, associated with fragmentation of the glomerular capillaries (black strands)
22
Q

What is expected on EM in crescentic glomerulonephritis?

A

Fragmentation of glomerular caps

23
Q

What is seen here?

A

Crescentic glomerulonephritis

  • A fibrous crescent (green), associated with sclerosis of the underlying glomerular capillaries
24
Q

What are possible causes of crescentic glomerulonephritis?

A
  • ANCA associated
  • Pauci-immune
25
Q

Pathogenesis of crescentic GN?

A
  • Crescents forms when there is rupture of the glomerular capillary loops and fibrin is extruded into the urinary space
  • The parietal epithelial cells (cells lining Bowman’s capsule) proliferate to form the crescent, along with inflammatory cells.
  • Bowman’s capsule may rupture leading to interstitial inflammation, even granuloma formation.
26
Q

What is the standard treatment for the renal disease identified in the biopsy and how is the prognosis?

A
  • The standard treatment for ANCA-related crescentic GN is cyclophosphamide
  • Usually the patient responds well to therapy, especially in those with a kidney biopsy showing active and acute lesions
  • Renal function may return to near normal.
  • However, the disease may recur later and recurrences may be heralded by elevations of serum ANCA levels.
27
Q

Case 3)

  • A 6 year old child presented with a 5 day history of vomiting, diarrhea, and fever
  • The patient’s mother noted that the child had cola colored urine along with markedly decreased urine output
  • Swelling of the face, abdomen, and legs was noted physical examination.

Lab findings:

  • Serum creatinine 6.7 mg/dl
  • Normal serum C3 and C4 levels
  • Urine analysis 3+ blood and 3+ protein
  • Antistreptolysin O (ASO) titer was in process.
  • A renal biopsy was performed.

What renal syndrome is this?

A

Gross hematuria and is edematous, suggesting overlapping nephritic and nephrotic syndrome

28
Q

What would a positive ASO titer suggest?

A

Previous strep infection (possibly strep throat or skin infection)

  • Titer elevations may suggest post-infectious GN
29
Q

What is seen on this biopsy?

A

Post-infectious glomerulonephritis

  • Glomeruli are cellular and small crescent is noted (arrow)
  • Diffuse endocapillary proliferation with many neutrophils (“exudative glomerulonephritis”) with crescent formation
30
Q

What is expected to be seen in EM of Post-infectious glomerulonephritis?

A
  • Epimembranous “humps” by electron microscopy
31
Q

What is expected to be seen in IF of Post-infectious glomerulonephritis?

A
  • Coarse globular deposits are seen on C3 immunofluorescence staining and correspond to epimembranous “humps” by electron microscopy
32
Q

What is seen here?

A

Post-infectious glomerulonephritis

  • Contains many neutrophils (“exudative glomerulonephritis”)
33
Q

What is seen here?

A

Post-infectious glomerulonephritis

  • Trichrome staining shows large red collections (“humps” on the GBM(arrows and inset)
34
Q

Case 3 cont’d)

  • Child diagnosed with Post-infectious glomerulonephritis and treated with steroids
  • The child responds well to steroids and is discharged home and seen in follow-up over the next year
  • 15 months after the original hospitalization there is recurrent hematuria and edema. Another renal biopsy is performed

What does it show? What is this?

A

Dense deposit disease (DDD), formerly known as MPGN type II

  • Hypercellular glomeruli; increased matrix but no crescents or neutrophils are seen
  • The glomerular basement membranes appear thickened and eosinophilic on PAS stain with some reduplication on Jones staining
  • Linear “sausage-like” intramembranous densities are seen on EM.
35
Q

What is seen here?

A

Dense deposit disease (DDD), formerly known as MPGN type II

  • On PAS the basement membranes appear thickened with some reduplication on Jones stain.
36
Q

What is expected on EM with Dense deposit disease (DDD), formerly known as MPGN type II?

A
  • On EM thick section the GBM appears ribbon like (black arrow)
  • Ultrastructural examination shows increased density and darkening of the lamina densa of the GBM (yellow arrow).
37
Q

What is seen here?

A

Dense ribbon like expansion of the GBM in dense deposit disease (DDD), also known as MPGN type II (see schematic ).

38
Q

How does type II change the diagnosis?

A
  • PIGN has a good prognosis (many are self-resolving) with only rare patients progressing to chronic renal failure.
  • DDD quickly progresses to end stage disease (50% of patients in 10 years) and often recurs after transplant.
  • DDD occurs due to abnormalities in the alternative complement pathway (C3 glomerulopathies). Humps may be seen and PIGN may precede development of DDD.
39
Q

In nephrotic syndrome, what part of the glomerulus is damaged? Result?

A
  • Increased permeability of GBM -> leak of protein (heavy proteinuria, hypoalbuminemia, hyperlipidemia, edema)

Could be due to:

  • Charge issues (increased matrix of GBM with diabetes or electron dense deposits with membranous glomerulonephropathy)
  • Podocyte changes (effaced foot processes like in minimal change disease or focal segmental glomerulonphritis)
  • Diffuse!

Think: chain link fence intact but missing privacy screen (podocyte processes)

40
Q

In nephritic syndrome, what part of the glomerulus is damaged? Result?

A
  • Disruption of capillary loops with spillage of protein and red cells -> active urinary sediment
  • Spilled proteins may incite crescent formation
  • FOCAL PROCESS ALONG THE GBM!

Think: car driving through opening in totally intact chain link fence

  • GBM underlying structure may be intact but it is disrupted in regions (the gate is open)