• AL amyloidosis
• MGRS
• light chain cast nephropathy
• monoclonal gammopathy of renal significance
• multiple myeloma

• AKI
• HTRA1
• Lupus nephritis
• Masked IgG
• Subepithelial EDD

• Glomerular antigens
• Immunofluorescence
• Immunoglobulin subclass
• Immunohistochemistry
• Paraffin-IF

• gammopathy
• kidney
• monoclonal
• pathogenesis
• plasma cells
• renal
• significance
• treatment

• C3G
• C3GN
• Exostosin
• FAT1
• GVHD
• MGMID
• MPGN
• NCAM1
• NELL1
• PGNMID
• PLA2R
• Semaphorin 3B
• TGFBR3
• TMA
• aHUS
• antigens
• dense deposit disease
• glomerulonephritis
• infection-related
• kidney
• lupus
• membranous nephropathy
• monoclonal
• paraffin IF
• post-infectious
• renal pathology

• Humans
• Child
• Glomerulonephritis/diagnosis
• Glomerulonephritis/pathology
• Glomerulonephritis/immunology
• Glomerulonephritis/metabolism
• Glomerulonephritis, Membranous/diagnosis
• Glomerulonephritis, Membranous/immunology
• Glomerulonephritis, Membranous/pathology
• Kidney Glomerulus/pathology
• Kidney Glomerulus/metabolism

• Electrophoresis
• Glomerulonephritis
• Immunoglobulin
• Nephrotic syndrome
• Plasma cells

• IA/CPHS/22/1/506541 DBT-Wellcome Trust India Alliance

• Amyloidosis
• Cryoglobulinemia
• Glomerular disease
• Immunotactoid glomerulopathy
• Light chain deposition disease
• Monoclonal gammopathy
• Nephrotic syndrome
• Paraproteinemia

• Humans
• Paraproteinemias/pathology
• Paraproteinemias/diagnosis
• Paraproteinemias/metabolism
• Glomerulonephritis/pathology
• Glomerulonephritis/metabolism
• Glomerulonephritis/diagnosis
• Kidney Glomerulus/pathology
• Kidney Glomerulus/metabolism
• Paraproteins/metabolism
• Kidney Diseases/pathology
• Kidney Diseases/metabolism
• Biopsy
• Amyloidosis/pathology
• Amyloidosis/metabolism
• Amyloidosis/diagnosis

• IgM kappa
• MGRS
• monoclonal immunoglobulin deposition
• nocardiosis dermatitis
• proliferative glomerulonephritis

• complement
• fibrosis
• glomerular disease
• gn
• immunology and pathology

• Humans
• Kidney Diseases/pathology
• Kidney Glomerulus/pathology
• Mass Spectrometry
• Laser Capture Microdissection/methods
• Glomerulonephritis, Membranous/metabolism
• Amyloidosis

• P30 CA015083 NCI NIH HHS

• Immunofluorescence
• Kidney
• Renal pathology
• Review

• Diabetes
• membranous nephropathy
• nondiabetic kidney disease

• Humans
• Glomerulonephritis, Membranous/complications
• Glomerulonephritis, Membranous/diagnosis
• Kidney Glomerulus
• Glomerulonephritis

• antigen retrieval
• direct immunofluorescence
• formalin-fixed paraffin-embedded sections
• kidney disease
• proteinase

• C3 glomerulopathy
• complement alternative pathway
• infection-related glomerulonephritis
• membranoproliferative glomerulonephritis
• nephritis-associated plasmin receptor

• Autoantibodies
• Membranous Glomerulonephritis and Masked IgG-Kappa deposits
• Membranous nephropathy
• SSA

• Università degli Studi di Torino

In several published research, the evaluation of renal disorders using immunofluorescence on formalin-fixed, paraffin-embedded (FFPE) tissue sections versus immunofluorescence on frozen sections was compared. Each technique's accuracy varies greatly. This study's objective was to assess IF-P as a potential replacement for IF-F in the diagnosis of renal biopsy specimens.

To show immunoglobulin IgA, IgG, IgM, and C3 immune deposits, proteinase K digestion of paraffin-embedded renal biopsy was standardized and used in 51 renal biopsies. Sensitivity, specificity, false-positive, and false-negative values were calculated.

IF-P showed a sensitivity of 93.1%, 76.9%, 63.6%, and 33.3%, and a specificity of 100%, 97.3%, 95%, and 100% for IgG, IgA, IgM, and C3, respectively. Compared to cases that had both routine IF and IF-P, 50 of 51 showed either the same amount of staining for the diagnostic immunoglobulin/complement or a small amount of difference. In most of the cases (49 of 51), diagnostic findings were found.

IF-P is a sensitive and precise approach for assessing immune deposits in renal tissue biopsies. We come to the conclusion that IF-P serves as a beneficial salvage immunohistochemistry method for renal biopsies that do not contain enough cortical tissue for IF-F.

Nephritis-associated plasmin receptor (NAPlr) was originally isolated from the cytoplasmic fraction of group A Streptococci, and was found to be the same molecule as streptococcal glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and plasmin receptor (Plr) on the basis of nucleotide and amino acid sequence homology. Its main functions include GAPDH activity, plasmin-binding capacity, and direct activation of the complement alternative pathway (A-P). Plasmin trapped by deposited NAPlr triggers the degradation of extracellular matrix proteins, such as glomerular basement membranes and mesangial matrix, and the accumulation of macrophages and neutrophils, leading to the induction of plasmin-related endocapillary glomerular inflammation. Deposited NAPlr at glomerular endocapillary site directly activates the complement A-P, and the endocapillary release of complement-related anaphylatoxins, C3a and C5a, amplify the in situ endocapillary glomerular inflammation. Subsequently, circulating and in situ-formed immune complexes participate in the glomerular injury resulting in NAPlr-mediated glomerulonephritis. The disease framework of infection-related glomerulonephritis (IRGN) has been further expanded. GAPDH of various bacteria other than Streptococci have been found to react with anti-NAPlr antibodies and to possess plasmin-binding activities, allowing glomerular NAPlr and plasmin activity to be utilized as key biomarkers of IRGN.

• Biomarkers
• Fibrinolysin
• Glomerulonephritis/metabolism
• Glyceraldehyde-3-Phosphate Dehydrogenases
• Humans
• Inflammation
• Nephritis
• Receptors, Peptide
• Streptococcal Infections

• Biopsy
• Female
• Fluorescent Antibody Technique
• Glomerulonephritis
• Humans
• Immunoglobulin G/metabolism
• Kidney/metabolism
• Male
• Staining and Labeling

• Dysproteinemia
• Kidney disease
• Monoclonal gammopathy
• Monoclonal gammopathy of renal significance
• Monoclonal protein

• Direct immunofluorescence
• FFPE
• Fresh-frozen
• Immunofluorescence
• Immunohistochemistry
• Indirect immunofluorescence

• Antibodies
• Antigens
• Fluorescent Antibody Technique
• Formaldehyde
• Immunohistochemistry
• Laboratories, Clinical
• Paraffin Embedding
• Tissue Fixation

• antigen
• autoimmune profiling
• epitope spreading
• mass spectrometry
• membranous lupus nephritis
• membranous nephropathy
• serologic testing

• Autoantigens/immunology
• Glomerulonephritis, Membranous/immunology
• Humans

• Adolescent
• Kidney biopsy
• MGMID
• Membranous-like glomerulopathy with masked IgG kappa deposits
• Paraffin IF
• Petechial rash

Membranous nephropathy (MN) is the leading cause of nephrotic syndrome in adults worldwide. A growing body of evidence indicates a pathogenic and autoimmune correlation between Helicobacter pylori infection, MN, and autoimmune liver disease.

A 47-year-old African American woman presented to our institution with epigastric pain and vomiting. In-patient hospital workup included a thorough abdominal evaluation including esophagogastroduodenoscopy and liver biopsy, which revealed active H. pylori infection and autoimmune hepatitis. The patient was incidentally also found to have nephrotic-range proteinuria. Renal workup including kidney biopsy established the diagnosis of MN. Proteinuria improved after initiation of triple therapy for H. pylori infection.

This case adds to the growing evidence of a correlation between H. pylori infection, MN, and autoimmune liver disease. This report demonstrates a unique case of a patient with MN, autoimmune hepatitis (AIH)/primary biliary cholangitis (PBC), and HP who underwent triple-eradication antibiotic treatment that resulted in an ultimate resolution of all these conditions.

• Autoimmune diseases
• Case report
• Helicobacter pylori infection
• Hepatitis
• Kidney biopsy
• Membranous nephropathy
• Nephrotic syndrome
• Proteinuria

• Membranous nephropathy
• Membranous-like glomerulopathy with masked IgG-κ deposits
• Sjögren’s syndrome

• MGRS
• monoclonal fibrillary glomerulonephritis
• monoclonal gammopathy
• paraffin immunofluorescence
• pronase immunofluorescence

• C3 glomerulopathy
• KDIGO
• anti-neutrophil cytoplasmic antibody–associated vasculitis
• focal and segmental glomerulosclerosis
• lupus nephritis
• membranoproliferative glomerulonephritis
• minimal change disease
• monoclonal gammopathies of renal significance

There are few published studies comparing immunofluorescence on formalin-fixed, paraffin-embedded (FFPE) tissue sections (IF-P) and immunoperoxidase on FFPE tissue sections (IP-P) with immunofluorescence on frozen sections (IF-F) for evaluation of renal diseases. Also, the accuracy for each method differs greatly. The aim of this study was to evaluate IF-P and IP-P as an alternative to IF-F (gold standard method) in the diagnosis of renal biopsies specimens.

In all, 101 renal biopsies were subjected to IF-P, IP-P, and IF-F staining to demonstrate immunoglobulin IgA, IgG, and IgM immune deposits. Sensitivity, specificity, false-positive, and false-negative values were calculated.

IP-P showed sensitivity of 61.8%, 74.2%, and 64.2%, and specificity of 84.8%, 69.2%, and 66.7% for IgA, IgG, and IgM, respectively. IF-P showed a sensitivity of 45.6%, 69.4% and 52.8%, and specificity of 87.9%, 87.2% and 77.1% for IgA, IgG and IgM, respectively. False-positive cases of IF-P and IP-P were 4, 5, and 11 and 5, 12, and 16 for IgA, IgG, and IgM, respectively.

Where IF-F lacks glomeruli or fresh renal biopsies are not available, IP-P is a sensitive method, whereas IF-P is a specific method for the evaluation of immune deposits in the renal tissue biopsies. The presence of false-positive cases in both methods deserves further research.

• Frozen sections
• immunofluorescence
• immunoperoxidase
• paraffin sections
• renal biopsy

Membranous-like glomerulopathy with masked IgG kappa deposits (MGMID) is a recently described pattern of glomerulonephritis with a unique histopathology. The pattern is characterized by subepithelial and/or mesangial immune deposits that are “masked”, to immunoglobulin staining by routine immunofluorescence but strongly stain for IgG and kappa light chain after protease digestion. Patients with this pattern of glomerulonephritis are most commonly young females presenting with proteinuria and a vague history of autoimmune disease such as low titer antinuclear antibodies. Here we compared the mass spectrometry profile of laser capture microdissected glomeruli from nine MGMID renal biopsies with eight biopsies showing other patterns of membranous glomerulopathy. The protein most significantly increased in MGMID was serum amyloid P. Immunostaining showed serum amyloid P colocalized with IgG in the glomeruli of MGMID but not with PLA2R-associated membranous glomerulopathy. Serum amyloid P was positive in the glomeruli of all 32 MGMID biopsies but negative in biopsies of other types of membranous glomerulopathies such as those associated with PLA2R and THSD7A. There were four biopsies with glomerular serum amyloid P staining among the 173 biopsies that did not fulfill criteria for MGMID or amyloidosis. All four of these biopsies with positive serum amyloid P staining had a membranous pattern of glomerulopathy with IgG kappa deposits that only differed from MGMID by the lack of “masking”. Thus, positive staining within glomerular deposits for serum amyloid P identifies a unique form of glomerulonephritis likely sharing a common pathophysiologic mechanism of disease.

• glomerulonephritis
• masked deposits
• mass spectrometry
• membranous-like glomerulopathy
• subepithelial deposits

• MPGN
• monoclonal gammopathy
• monoclonal gammopathy of renal significance
• proliferative glomerulonephritis with monoclonal IgG deposits (PGNMID)

• PLA2R
• membranous glomerulonephritis
• membranous‐like glomerulonephritis
• nephrotic syndrome
• spikes
• weak immunoglobulin deposition for IgG

For decades, kidney diseases related to inappropriate complement activity, such as atypical hemolytic uremic syndrome and C3 glomerulopathy (a subtype of membranoproliferative glomerulonephritis), have mostly been complicated by worsened prognoses and rapid progression to end-stage renal failure. Alternative complement pathway dysregulation, whether congenital or acquired, is well-recognized as the main driver of the disease process in these patients. The list of triggers include: surgery, infection, immunologic factors, pregnancy and medications. The advent of complement activation blockade, however, revolutionized the clinical course and outcome of these diseases, rendering transplantation a viable option for patients who were previously considered as non-transplantable cases. Several less-costly therapeutic lines and likely better efficacy and safety profiles are currently underway. In view of the challenging nature of diagnosing these diseases and the long-term cost implications, a multidisciplinary approach including the nephrologist, renal pathologist and the genetic laboratory is required to help improve overall care of these patients and draw the optimum therapeutic plan.

• Complement-related diseases
• Kidney transplantation
• De novo
• Recurrent diseases

Thrombotic microangiopathy (TMA) is one of the most devastating sequalae of kidney transplantation. A number of published articles have covered either de novo or recurrent TMA in an isolated manner. We have, hereby, in this article endeavored to address both types of TMA in a comparative mode. We appreciate that de novo TMA is more common and its prognosis is poorer than recurrent TMA; the latter has a genetic background, with mutations that impact disease behavior and, consequently, allograft and patient survival. Post-transplant TMA can occur as a recurrence of the disease involving the native kidney or as de novo disease with no evidence of previous involvement before transplant. While atypical hemolytic uremic syndrome is a rare disease that results from complement dysregulation with alternative pathway overactivity, de novo TMA is a heterogenous set of various etiologies and constitutes the vast majority of post-transplant TMA cases. Management of both diseases varies from simple maneuvers, e.g., plasmapheresis, drug withdrawal or dose modification, to lifelong complement blockade, which is rather costly. Careful donor selection and proper recipient preparation, including complete genetic screening, would be a pragmatic approach. Novel therapies, e.g., purified products of the deficient genes, though promising in theory, are not yet of proven value.

• Kidney transplantation
• De novo thrombotic microangiopathy
• Thrombotic microangiopathy
• Recurrent thrombotic microangiopathy
• Atypical hemolytic uremic syndrome

• masked deposits
• masked monoclonal deposits
• paraffin immunofluorescence
• pronase immunofluorescence

• False-negative
• Immunotactoid glomerulopathy
• Monoclonal gammopathy of renal significance
• Monoclonal gammopathy of undetermined significance

• C3
• Complement
• Glomerulonephritis
• Immune deposits
• Renal biopsy

• Complement C3/metabolism
• Fluorescent Antibody Technique
• Glomerular Mesangium/metabolism
• Glomerular Mesangium/pathology
• Glomerulonephritis/drug therapy
• Glomerulonephritis/immunology
• Glomerulonephritis/metabolism
• Glomerulonephritis/pathology
• Humans
• Male
• Middle Aged
• Prognosis

• Adult
• B-Lymphocytes
• Biopsy
• Calcineurin Inhibitors
• Chronic
• Cyclophosphamide
• Glomerulonephritis
• Humans
• Immunoglobulin G
• Kidney Failure
• Kidney Glomerulus
• Lipoid
• Membranous
• Nephrosis
• PLA2R
• PLA2R1 protein
• Phospholipase A2
• Podocytes
• Receptors
• Remission
• Renal Insufficiency
• Spontaneous
• Staining and Labeling
• THSD7A
• congenital
• human
• membranous nephropathy
• nephrotic syndrome
• proteinuria

• Autoantibodies/blood
• Biomarkers/blood
• Disease Progression
• Glomerulonephritis, Membranous/diagnosis
• Glomerulonephritis, Membranous/drug therapy
• Glomerulonephritis, Membranous/epidemiology
• Glomerulonephritis, Membranous/immunology
• Humans
• Immunoglobulin G/blood
• Immunosuppressive Agents/therapeutic use
• Kidney/drug effects
• Kidney/immunology
• Kidney/pathology
• Receptors, Phospholipase A2/immunology
• Remission Induction
• Risk Factors
• Thrombospondins/immunology
• Time Factors
• Treatment Outcome

C3 glomerulopathy is a recently defined entity that encompasses a group of kidney diseases caused by abnormal control of complement activation with deposition of complement component C3 in glomeruli leading to variable glomerular inflammation. Before the recognition of the unique pathogenesis of these cases, they were variably classified according to their morphological features. C3 glomerulopathy accounts for roughly 1% of all renal biopsies. Clear definition of this entity has allowed a better understanding of its pathogenesis and clinical course and is likely to lead to the design of rational therapies over the next few years.

• C3 complement
• glomerular inflammation
• renal pathology

• C3 glomerulopathy
• anti-complement therapies
• atypical hemolytic uremic syndrome
• complement
• glomerulonephritis
• kidney disease

• Amyloidosis
• Immunoglobulin G
• Kidney Glomerulus
• Paraproteinemias
• Paraproteins
• Thrombotic Microangiopathies
• amyloidosis
• cancer
• cryoglobulinemia
• fibrillary glomerulonephritis
• glomerular disease
• glomerulonephritis
• immunotactoid glomerulopathy
• light chain deposition disease
• multiple myeloma
• nephrotic syndrome

• Amyloidosis/complications
• Amyloidosis/drug therapy
• Cryoglobulinemia/complications
• Glomerulonephritis/immunology
• Glomerulonephritis/pathology
• Glomerulonephritis, Membranoproliferative/immunology
• Glomerulonephritis, Membranoproliferative/pathology
• Glomerulonephritis, Membranous/immunology
• Humans
• Immunoglobulin G/metabolism
• Immunoglobulin Heavy Chains/metabolism
• Immunoglobulin Light Chains/metabolism
• Kidney Diseases/drug therapy
• Kidney Diseases/immunology
• Kidney Diseases/pathology
• Kidney Glomerulus
• Paraproteinemias/complications
• Paraproteins/metabolism
• Thrombotic Microangiopathies/complications

To describe the technique of immunofluorescence on paraffin embedded tissue sections and discuss the potential pitfalls with an in depth review of literature.

Immunofluorescence is integral to diagnostic renal pathology. Immunofluorescence on paraffin embedded renal biopsies (IF-P) after enzyme treatment has been described in literature, however has not found widespread use in renal pathology laboratories. In our laboratory proteinase K digestion of paraffin embedded renal biopsy material was standardized and applied prospectively in cases where immunofluorescence on fresh frozen tissue was non contributory or not possible. Diagnostic utility was assessed and in a cohort of cases comparison of intensity of staining with routine immunofluorescence was performed.

Over the 5-year study period, of the 3141 renal biopsies received IF-P was performed on 246 cases (7.7%) and was interpretable with optimal digestion in 214 cases (6.8%). It was of diagnostic utility in the majority of cases, which predominantly included glomerular disease. Non-diagnostic IF-P was found in membranous nephropathy (2 of 11 cases), membranoproliferative glomerulonephritis (2 of 32 cases), lupus nephritis (1 of 25 cases), post infectious glomerulonephritis (1 of 11 cases) and chronic glomerulonephritis (3 of 8 cases). Comparing cases with both routine IF and IF-P, 35 of 37 showed either equal intensity or a minor difference in intensity of staining (1+) for the diagnostic immunoglobulin/complement. Technically assessment of immunofluorescence on the paraffin embedded tissue was found to be easier with clearly observed morphology, however a false positive staining pattern was observed in under-digested tissue.

As a “salvage” technique, immunofluorescence on paraffin embedded renal biopsies is of great diagnostic utility, however not without pitfalls.

• Immunofluorescence on paraffin section
• Renal biopsy
• Salvage technique
• Enzymatic digestion
• Proteinase K

Ig deposits identified on renal biopsy samples by paraffin immunofluorescence that show negative staining by routine immunofluorescence on frozen tissue have become known as “masked” deposits. Membranous-like glomerulopathy with masked IgG kappa (κ) deposits is a recently recognized pattern of immune complex deposition characterized by masked deposits that show IgG κ restriction and are subepithelial and mesangial by electron microscopy. Based on the frequent presence of C3-only staining by routine immunofluorescence microscopy (IF), these cases could be misdiagnosed as C3 glomerulonephritis in the absence of paraffin immunofluorescence evaluation.

The clinicopathologic details of all cases of membranous-like glomerulopathy with masked IgG κ deposits diagnosed in our laboratory were included, beginning with the initial recognition of this entity in 2011 through the end of 2015. Inclusion was based on renal biopsy sample morphologic features including glomerular deposits that stain for IgG κ and have a staining intensity that is significantly brighter by paraffin IF than by routine IF on frozen tissue.

This pattern of immune complex deposition has been seen in 41 patients in our laboratory over a 5-year period. The patients with these biopsy findings are most commonly young female individuals with a mean age of 27.5 years, with 88% being less than 40 years. All patients had proteinuria with a mean 24-hour urine protein of 3.5 g (range 0.5−12.8 years) and 35% with nephrotic-range proteinuria. Hematuria was present in 88% of patients, and 29% had elevated serum creatinine at presentation. Autoimmune serologic tests were positive in 55% of patients, with a weakly positive antinuclear antibody being most common. Despite this, only 1 patient (2%) fulfilled the diagnostic criteria for systemic lupus erythematosus. The outcome data were mixed, as some patients showed spontaneous remission and mild disease whereas others progressed to end-stage renal disease. There was no apparent correlation between the treatment used and outcome in this retrospective analysis. One patient underwent transplantation and developed biopsy-proven recurrence of disease in the graft 42 months posttransplantation. The etiology of this entity remains unknown.

We provide an expanded case series detailing the clinicopathologic findings of patients with membranous-like glomerulopathy with masked IgG κ deposits. Patients are most commonly young female individuals <40 years of age and commonly have positive autoimmune serologic studies such as antinuclear antibody, although few carry a diagnosis of any well-defined autoimmune disease such as lupus. The outcome data were mixed, as some patients showed spontaneous remission and mild disease whereas others progressed to ESRD. There was no apparent correlation between the treatment used and outcome in this retrospective analysis.

• C3 glomerulonephritis
• masked deposits
• membranous glomerulopathy
• nephritis
• proliferative glomerulonephritis with monoclonal IgG kappa deposits
• renal biopsy