Membranous nephropathy is characterized by thickening of the glomerular capillary wall and subepithelial immune deposits. It is most commonly caused by antibodies against the phospholipase A2 receptor (PLA2R). Treatment involves immunosuppression like cyclophosphamide and corticosteroids to induce remission, as incomplete or no remission is associated with worse long-term outcomes like end stage renal disease. Recurrence after kidney transplantation is common in PLA2R antibody positive patients and predicts poor allograft survival.

1. MEMBRANOUS
NEPHROPATHY

2. INTRODUCTION
• The term membranous refers to thickening of the glomerular capillary
wall on light microscopy of a renal biopsy
• Membranous nephropathy is defined by immunofluorescence and
electron microscopy (EM).
• Immune deposits of immunoglobulin G (IgG) and complement
components beneath podocytes on the subepithelial surface of the
glomerular capillary wall
• Most common cause of primary nephrotic syndrome in older (>60
years)

3. PRIMARY MN
• Anti-PLA2R associated (70%-80%)
• Idiopathic (20%-30%)
• Anti-THSD7A (up to 5%)

4. SECONDARY MN
Infections
HBV, HCV, HIV, parasites (filariasis,
schistosomiasis, malaria), leprosy,
syphilis, hydatid disease, sarcoid
Malignancy
Solid tumors (lung 26%, prostate
15%, hematologic [plasma cell
dyscrasias, non-Hodgkin
lymphoma, CLL] 14%, colon 11%),
mesothelioma, melanoma,
pheochromocytoma; some benign
tumors

5. Autoimmune diseases
SLE (class V), thyroiditis, diabetes, rheumatoid arthritis,
Sjogren syndrome, dermatomyositis, mixed connective
tissue disease, ankylosing spondylitis, retroperitoneal
fibrosis, renal allografts
Anti-GBM disease, IgAN, ANCA-associated vasculitis
IgG4 disease
Membranous-like glomerulopathy with masked
IgG κ deposits

6. Alloimmune
diseases
Graft versus host disease, autologous stem cell transplants,
de novo MN in transplants/transplant glomerulopathy
Fetometernal alloimmunization to neutral endopeptidase
Drugs/toxins
NSAIDs and cyclooxygenase-2 inhibitors, gold, d-penicillamine,
bucillamine, captopril, probenecid, sulindac, anti-TNFα, thiola,
trimetadione, tiopronin
Mercury, lithium, hydrocarbons, formaldehyde, environmental air
pollution (China)
Miscellaneous
Cationic Bovine Serum Albumin (infants)
Sarcoidosis

7. Experimental Membranous Nephropathy
• Heymann nephritis model of MN in rats - late 1970s
• Subepithelial immune deposits form in situ when circulating
antibodies bind to an intrinsic antigen in the glomerular capillary wall
• Antigen was subsequently identified as megalin,(internsic)
• A large (~600 kD) transmembrane receptor of the low-density lipoprotein
receptor family expressed on the basal surface of rat podocytes
• Capping and shedding of the antigen-antibody complexes, where they
bind to the underlying GBM, resist degradation, and persist for weeks
or months as immune deposits characteristic of MN
• Sublethal podocyte injury induced by the complement membrane
attack complex C5b-9

8. • Podocyte foot process effacement is likely the result of the collapse of
the actin cytoskeleton and loss of cell-GBM adhesion complexes, and
the loss and displacement of slit diaphragms are associated with the
onset of severe, nonselective proteinuria
• ECM proteins that are laid down between and around the immune
deposits, giving rise to the characteristic “spikes” and GBM thickening
that are hallmarks of MN
• Planted antigens - ainimal models immunized with cationized bovine
serum albumin (cBSA). The cBSA binds to negatively charged residues
in the GBM where it serves as a target for circulating anti-BSA
antibodies

11. Human Membranous Nephropathy
• First demonstration of an intrinsic podocyte antigen -by an unusual
case of antenatal MN induced by the transplacental passage of
alloantibodies to neutral endopeptidase (NEP), a known podocyte
protein
• The mother of the affected child was found to be deficient in NEP and
had been immunized during a previous pregnancy
• Same mechanism seen in
• de novo MN after renal transplantation and
• MN in the setting of chronic graft-versus-host disease after allogeneic
hematopoietic stem cell transplantation

13. •AUTOANTIBODIES
•PLA2R
• autoantibodies directed at the M-type phospholipase
A2 receptor (PLA2R) on podocytes
• 75% to 80% of patients with primary MN
• IgG4
•THSD7A
• thrombospondin type 1 domain–containing 7A
• 5% of cases of primary MN

14. • Planted antigen mechanism in MN
• children with MN who have been exposed to cBSA,
presumably in bottled milk
• class V (membranous) lupus nephritis and
• hepatitis B virus (HBV)–associated MN

15. Serum Antibody (±) Glomerular Antigen (±)
Percent of Patients Who
Underwent Biopsy, %
Diagnosis
Anti-PLA2R (+) PLA2R (+) 70
PLA2R-mediated PMN
(active)
Anti-PLA2R (−) PLA2R (+) 15
PLA2R-mediated PMN
(inactive)
Anti-THSD7A (+) THSD7A (+) 3–5
THSD7A-mediated PMN
(active)
Anti-THSD7A (−) THSD7A (+) Unknown
THSD7A-mediated PMN
(inactive)
Anti-PLA2R/THSD7A (−) PLA2R/THSD7A (−) 10
Non-PLA2R/THSD7A–
mediated (pathogenesis
unknown)a

16. Pathology
• STAGE I
• Characteristic changes in MGN are in the glomerular capillary
walls.
• The initial phase of the glomerulopathy is marked by subepithelial
granular deposits
• Seen with light microscopy
• Trichrome stain-fuchsinophilic
• Methenamine-silver stain, -mottled aspect or very small orifices (“holes”)
• Can be missed if we do not have immunofluorescence (IF) or
electron microscopy (EM); these deposits are immune and will be
positive for IgG and, in most of cases, for C3, in addition, they are
electron-dense

18. • STAGE II
• Glomerular architecture is preserved and the capillary
walls appear thickened with routine stains
• Cellularity usually is not increased (if present it suggests a
secondary MGN)
• Projections perpendicularly to this GBM: “spikes” are seen
• Spikes are originated in reaction to the deposits and go
progressively surrounding them (type IV collagen)

21. • STAGE III
• Forming thus new layers of GBM leaving the deposits
immersed
• Deposits are seen intramembranous and with silver stain
capillary walls can take an aspect in “chain” or “rosary”
• Positive with the immunostaining (IF), although
progressively they are less electron-dense

23. •STAGE IV
•The GBM is irregularly thickened
•Without the presence of electron-dense deposits or
holes.
•In this phase it is considered that the deposits have
been resorpted leaving this irregular aspect.

25. IMMUNOFLUORESCENCE
• Granular parietal IgG positivity
• C3 deposits in approximately 75% of cases.
• The IgG immunostaining usually is more intense than C3.
• IgG4 sub-class is the most frequent

27. Primary Secondary
Immunofluorescence Microscopy
IgG4 > IgG1, IgG3 IgG1, IgG3 > IgG4
IgA, IgM absent IgA, IgM may be present
Mesangial Ig staining absent Mesangial Ig staining may be present
C1q negative or weak C1q positive
PLA2R positive and co-localizes with IgG PLA2R negative
Electron Microscopy
Subepithelial deposits only ± mesangial
rarely
Subepithelial deposits ± mesangial and
subendothelial deposits

28. ELECTRON MICROSCOPY
• Electron-dense deposits in the epithelial aspect (external) of the
GBM, between this one and the epithelial cell: subepithelials or
epimembranous
• Spikes are demonstrated as irregular projections of the GBM

31. CLINICAL FEATURES
• Rare in children: Less than 5% of total cases of nephrotic syndrome
• Common in adults: 15% to 50% of total cases of nephrotic syndrome,
depending on age; increasing frequency after 40
• Males > females in all adult groups
• Nephrotic syndrome in 60% to 70%
• Normal or mildly elevated blood pressure at presentation
• Benign urinary sediment
• Nonselective proteinuria
• Tendency to thromboembolic disease
• Other features of secondary causes: Infection, drugs, neoplasia,
systemic lupus erythematosus

32. Clinical features-correlating to Anti PLA2R
• 70%–80% of patients with PMN have anti-PLA2R/THSD7A antibody
• Anti-PLA2R antibody is about 80% sensitive and 100% specific for
PMN
• Anti-PLA2R antibody can be present for many months before
proteinuria appears
• In non-nephrotic patients, low, or declining, anti-PLA2R levels predict
spontaneous remission and high levels predict progression to
nephrotic syndrome
• Anti-PLA2R–negative patients can become positive later
• High antibody levels (before and after treatment) correlate with
proteinuria, response to therapy, and (after therapy) long-term
outcomes

33. • Patients with higher antibody levels require more prolonged
immunosuppression to achieve remission rates comparable to those
with lower levels
• Expansion of the specificity of anti-PLA2R antibody to include
additional epitopes (epitope spreading) correlates with a worse
prognosis
• Anti-PLA2R levels go down in remission and return with relapse
• Elevated anti-PLA2R levels after treatment predict relapse
• Elevated anti-PLA2R levels at the time of transplantation predict
recurrence
• Disappearance of anti-PLA2R antibodies (immunologic remission)
precedes renal remission (disappearance of proteinuria) by weeks to
months

34. • ELISA assay for PLA2R
• Cell-based ALBIA assay
(Mitogen Advanced
Diagnostics Laboratory,
Calgary, Canada)
ELISA assay, levels
>20 RU/ml are
considered positive

35. Predictors of Poor Outcome
Factors Predictor PPV (%)
Clinical Features
Age Older > younger 43
Gender Male > female 30
HLA type HLA/B18/DR 3/Bffl present 71
Hypertension Present 39
Serum Levels
Albumin <1.5 g/dL 56
Creatinine Above normal 61

36. Urine Protein
Nephrotic syndrome Present 32
Proteinuria >8 g for >6 months 66
IgG excretion >250 mg/day 80
β2-Microglobulin excretion >54 µg/mmol creatinine <54 79
C5b-9 excretion >7 mg/mg creatinine 67
Biopsy Changes
Glomerular focal sclerosis Present 34
Tubulointerstitial disease Present 48

37. TORANTO RISK SCORE
Low Risk Medium Risk High Risk
Normal serum
and creatinine
plus proteinuria
over 6 mo of
Normal or near-
creatinine clearance
persistent proteinuria
8 g/day over 6 mo
maximum
treatment
Deteriorating renal
function (>30%decline
GFR)and/or persistent
proteinuria >8 g/day
(up to 6) months of
observation

40. OUTCOME
Clinical Response Definition
Complete remission Proteinuria <0.3 g/d
Partial remission
>50% reduction from baseline and between 0.3
and 3.5 g/d
With stable GFR
No remission <50% reduction or >3.5 g/d
Relapse Recurrence of >3.5 g/d after remission
ESRD
GFR<15 ml/min or requirement for
dialysis/transplant

41. • Relapse from a complete remission occurs in approximately 25% to
40%
• Relapse rate is as high as 50% in those achieving only a partial
remission
• Review of 348 nephrotic patients with MN documented a 10-year
renal survival
• complete remission of 100%
• partial remission, 90%
• no remission, only 45%.
• A recent update suggested durability of remission, whether complete
or partial, drug-induced or spontaneous, is closely related to the long-
term outcome.
• Thus goal of therapy is Complete and partial remission

42. ST Regimen Drug, Dose Comments
Cytotoxic drugs KDIGO first choice
Modified Ponticelli
Months 1, 3, 5: 1 g
methylprednisolone iv on days 1, 2,
and 3 followed by oral prednisone,
0.5 mg/kg daily for 27 d
Monitor Uprotein and WBC weekly
×8, then every 2 mo; daily oral
prednisone and cyclophosphamide
may have similar efficacy. Increased
risk of malignancy above 36 g
Months 2, 4, 6: 2.0–2.5 mg/kg oral
cyclophosphamide daily
Relapse rate 20%–30%
Dutch protocol
Months 1, 3, 5: 1 g MP days 1–3
followed by oral prednisone, 0.5–1.0
mg/kg for 6 mo, then taper Same as above
Oral cyclophosphamide, 1.5–2.0
mg/kg daily for 12 mo

43. CNIs KDIGO second choice
Cyclosporin
3.5–5.0 mg/kg daily in divided doses adjusted
to level of 120–200 μg/L for 12–18 mo and
tapered
Used in patients resistant to cytotoxic drugs
but can be used as initial therapy. Taper slowly
Prednisone 5–10 mg daily or alt days
Discontinue at 6 mo if no response
Relapse rate 40%–50%
Tacrolimus
0.05–0.075 mg/kg daily in two divided doses
adjusted to level of 3–5 μg/L for 12–18 mo
and taper slowly
Same as above
Prednisone 5–10 mg/kg per day daily or alt
days
Preferable in young women
B cell depletion
Used for patients resistant to cytotoxic drugs
or CNIs
Utility as initial therapy not yet established by
RCTs
Rituximab
375 mg/M2 weekly times 4 Follow CD20 counts and repeat dose if counts
rise before remission in proteinuria or relapse
occurs
375 mg/M2 once and follow CD20/19 counts
1000 mg on days 1 and 15
ACTH
Tetracosactrin (Synacthen) (synthetic) 1 mg IM every 2 wk for 6–12 mo
Corticotropin (ACTHAR) (purified) 80 U IM every 2 wk for 6–12 mo

44. • MULTIDRUG THERAPY
• Rituximab with low-dose cyclophosphamide and an
accelerated taper of steroids reported a 100% remission
rate over a mean follow-up of 37 months
• Rituximab and CSA, achieved remissions in 92% and
antibody depletion in 100% in 9 months
• A combination of rituximab and plasma exchange showed
promise in a third small study

45. Transplantation in PMN
• In anti-PLA2R–positive patients, subepithelial deposits can appear in
the allograft within 6 days
• Proteinuria is seen within 13–15 months in about 40%–50% of
allografts and can diminish allograft survival
• Recurrence rate of subepithelial deposits in patients positive for anti-
PLA2R antibodies at the time of transplantation may approach 90%
• Anti-PLA2R–negative de novo MN is also a common cause of
transplant nephrotic syndrome, affecting about 2% of all renal
transplant recipients whose original disease was not MN

46. • Because patients with recurrent subepithelial deposits do not all go
on to manifest clinical recurrence, treatment for recurrent MN is
usually considered only when protein excretion reproducibly exceeds
1 g/d in patients with PMN or 4 g/d in patients with de novo MN
• Rituximab is usually added to regular immunosuppressive protocols,
which often already include CNIs -one dose of 200 mg

47. NEW THERAPY
• Belimumab, an inhibitor of B cell activation, in 11 anti-PLA2R–positive
patients reported a 90% reduction in anti-PLA2R levels and a
(delayed) 70% reduction in proteinuria in patients receiving monthly
iv doses of the drug over a period of 28 weeks

48. THANK U…