The value of PLA2R antigen and IgG subclass staining relative to anti-PLA2R seropositivity in the differential diagnosis of membranous nephropathy

The diagnostic performance of PLA2R and IgG subclass staining of kidney biopsies relative to anti-PLA2R seropositivity in the differentiation of primary and secondary membranous nephropathy (pMN, sMN) was examined. Besides PLA2R staining - which has a lower specificity than anti-PLA2R antibody serology - there is insufficient knowledge to decide which IgG1-4 subtype immunohistological patterns (IgG4-dominance, IgG4-dominance/IgG1-IgG4-codominance or IgG4-dominance/IgG4-codominance with any IgG subtype) could be used to distinguish between pMN and sMN.87 consecutive Hungarian patients (84 Caucasians, 3 Romas) with the biopsy diagnosis of MN were classified clinically as pMN (n = 63) or sMN (n = 24). The PLA2R and IgG subclass staining was part of the diagnostic protocol. Anti-PLA2R antibodies were determined by an indirect immunofluorescence test in 74 patients with disease activity.For pMN, the sensitivity of anti-PLA2R seropositivity was 61.1%, and the specificity was 90.0%; and similar values for PLA2R staining were 81.0%, and 66.7%, respectively. In all stages of pMN, IgG4-dominance was the dominant subclass pattern, while the second most frequent was IgG3/IgG4-codominance. The sensitivity and specificity scores were: IgG4-dominance 52.2% and 91.7%, IgG4-dominance/IgG3-IgG4-codominance 76.2% and 87.5%, IgG4-dominance/IgG1-IgG4-codominance 64.2% and 75%, and IgG4-dominance/codominance with any IgG subclass 92.1% and 70.8%, respectively. Anti-PLA2R seropositivity, glomerular PLA2R, and IgG4-dominance/codominance significantly correlated with each other. The IgG4 subclass was rarely encountered in sMN.In our series, IgG4-dominance had the highest specificity in the differentiation of MN, just as high as that for anti-PLA2R seropositivity. The specificity values of PLA2R staining and IgG4-dominance/codominance with any IgG subclass or IgG4-dominance/IgG1-IgG4 codominance were ≤ 75%. Apart from IgG4 dominance, IgG4-dominance/IgG3-IgG4-codominance also had good statistical value in differentiating pMN from sMN. As IgG subclass switching during the progression of pMN was not the feature of our cohort, pMN in Hungarian patients is presumed to be an IgG4-related disorder right from the start. Although anti-PLA2R seropositivity has become the cornerstone for diagnosing pMN, if a kidney biopsy evaluation is conducted, besides the staining of PLA2R antigen, the evaluation of IgG subclasses provides relevant information for a differential diagnosis. Even in cases with IgG4-dominance, however, malignancy should be thoroughly checked

Enyhe szövettani eltérések ellenére gyors progressziójú proliferativ glomerulonephritis monoklonális immunglobulin-G-depozitumokkal = Rapidly progressive proliferative glomerulonephritis with monoclonal immunoglobulin G deposits despite the mild histological changes. Case report

Absztrakt: A proliferativ glomerulonephritis monoklonális immunglobulin-G (IgG)-depozitumokkal entitást immunfluoreszcens vizsgálattal szemcsés mintázatú monoklonális IgG (többnyire IgG3-kappa), elektronmikroszkóppal elektrondenz depozitumok, fénymikroszkóppal jobbára membranoproliferativ vagy endocapillaris proliferativ laesio jellemzi; előfordulhatnak félholdak. A glomerulonephritist plazmasejt/B-sejt klón által szekretált immunglobulinmolekula lerakódása okozza; a biopszia időpontjában csupán a betegek harmadánál mutatható ki paraproteinaemia. A proteinuriához gyakran társul haematuria és valamilyen szintű veseelégtelenség, a betegek negyedénél alakul ki végstádiumú veseelégtelenség. Egy 62 éves nőbeteg gyors vesefunkció-romlásának hátterében a klinikai kép, a laboratóriumi és a képalkotó vizsgálatok nem támogattak praerenalis és postrenalis okot, illetve intrinsic vascularis vagy tubulointerstitialis eredetet. A proteinuria és a glomerularis microhaematuria alapján gyorsan progrediáló glomerulonephritist valószínűsítettünk. Az ez irányú kivizsgálás antineutrofil citoplazma-antitest, antiglomerularis bazálmembrán, sejtmagellenes ellenanyagok, illetve cryoglobulin tekintetében negatívnak bizonyult, a szérum-C3- és -C4-szint a normális tartományban volt. Vesebiopsziát végeztünk. Immunfluoreszcens vizsgálattal a mesangiumban IgG3-kappa-, C3- és C1q-pozitív szemcsés depozitumok látszottak, melyek ultrastrukturálisan elektrondenz depozitumoknak bizonyultak. Fénymikroszkóppal 2 heges és 29 nyitott glomerulust vizsgáltunk, az utóbbiakban csupán enyhe mesangialis sejtproliferatio mutatkozott. A glomerularis elváltozásokat enyhe arteriola hyalinosis, interstitialis fibrosis és tubulus atrophia kísérte. Proliferativ glomerulonephritis monoklonális IgG-depozitumokkal betegséget kórisméztünk (gyakorisága felnőtt natív vesebiopsziás anyagunkban 0,18%). A beteg hematológiai kivizsgálása paraproteint, myeloma multiplexet nem igazolt. Az enyhe morfológiai eltérések ellenére a veseelégtelenség előrehaladt, és a diagnózis felállítása után két héttel hemodialíziskezelést kellett kezdenünk. Szteroid, ciklofoszfamid, majd rituximab adása a vesefunkciót nem befolyásolta; a beteg krónikus hemodialízisprogramba került. Az esetismertetés tudomásunk szerint az első hazai közlés; nefrológiai érdekessége a gyorsan progrediáló glomerulonephritis szindróma és a szövettanilag látott enyhe elváltozások közötti szembetűnő eltérés. Orv Hetil. 2018; 159(38): 1567–1572. | Abstract: Proliferative glomerulonephritis with monoclonal immunoglobulin G (IgG) deposits is characterized by granular deposits of monoclonal IgG; histologically it has typically a membranoproliferative or endocapillary pattern, and seen electronmicroscopically there are dense deposits without substructure. Here, we present the case of a 62-year-old Caucasian woman who was admitted with rapidly progressive kidney failure. The patient’s status, the laboratory and imaging examinations did not support prerenal, postrenal and – among the intrinsic causes – vascular and tubulointerstitial origin. The proteinuria and dysmorphic microhematuria suggested rapidly progressive glomerulonephritis. Tests for anti-neutrophil cytoplasmic antibodies, anti-glomerular basement membrane, antinuclear antibodies and cryoglobulins were negative, the C3 and C4 levels were normal. The biopsy evaluation diagnosed proliferative glomerulonephritis with monoclonal IgG deposits because of mesangial granular deposits of IgG3-kappa, C3, and C1q, and ultrastructurally electron-dense deposits (incidence in our adult native kidney biopsy series: 0.18%). 31 glomeruli were assessed histologically. 29 glomeruli displayed mild mesangial hypercellularity, 2 glomeruli were globally sclerotic. Crescents were not observed. Mild arteriolar hyalinosis, interstitial fibrosis and tubular atrophy accompanied the glomerular alterations. In the postbiopsy evaluation, paraprotein or multiple myeloma was not detected. Despite the mild histological findings, the kidney failure progressed, and hemodialysis had to be started two weeks after the biopsy. Steroids, cyclophosphamide and rituximab did not affect her kidney function, and she remained on hemodialysis during the follow-up of 39 months. This report presents for the first time proliferative glomerulonephritis with monoclonal IgG deposits as the possible cause of rapidly progressive nephritic syndrome in the absence of pronounced glomerular proliferative, sclerotic or tubulointerstitial lesions. Orv Hetil. 2018; 159(38): 1567–1572

FHR-5 Serum Levels and CFHR5 Genetic Variations in Patients With Immune Complex-Mediated Membranoproliferative Glomerulonephritis and C3-Glomerulopathy

Factor H-related protein 5 (FHR-5) is a member of the complement Factor H protein family. Due to the homology to Factor H, the main complement regulator of the alternative pathway, it may also be implicated in the pathomechanism of kidney diseases where Factor H and alternative pathway dysregulation play a role. Here, we report the first observational study on CFHR5 variations along with serum FHR-5 levels in immune complex-mediated membranoproliferative glomerulonephritis (IC-MPGN) and C3 glomerulopathy (C3G) patients together with the clinical, genetic, complement, and follow-up data.A total of 120 patients with a histologically proven diagnosis of IC-MPGN/C3G were enrolled in the study. FHR-5 serum levels were measured in ELISA, the CFHR5 gene was analyzed by Sanger sequencing, and selected variants were studied as recombinant proteins in ELISA and surface plasmon resonance (SPR).Eight exonic CFHR5 variations in 14 patients (12.6%) were observed. Serum FHR-5 levels were lower in patients compared to controls. Low serum FHR-5 concentration at presentation associated with better renal survival during the follow-up period; furthermore, it showed clear association with signs of complement overactivation and clinically meaningful clusters.Our observations raise the possibility that the FHR-5 protein plays a fine-tuning role in the pathogenesis of IC-MPGN/C3G

Validation of distinct pathogenic patterns in a cohort of membranoproliferative glomerulonephritis patients by cluster analysis

Background: A novel data-driven cluster analysis identified distinct pathogenic patterns in C3-glomerulopathies and immune complex-mediated membranoproliferative glomerulonephritis. Our aim was to replicate these observations in an independent cohort and elucidate disease pathophysiology with detailed analysis of functional complement markers. ----- Methods: A total of 92 patients with clinical, histological, complement and genetic data were involved in the study, and hierarchical cluster analysis was done by Ward method, where four clusters were generated. ----- Results: High levels of sC5b-9 (soluble membrane attack complex), low serum C3 levels and young age at onset (13 years) were characteristic for Cluster 1 with a high prevalence of likely pathogenic variations (LPVs) and C3 nephritic factor, whereas for Cluster 2-which is not reliable because of the small number of cases-strong immunoglobulin G staining, low C3 levels and high prevalence of nephritic syndrome at disease onset were observed. Low plasma sC5b-9 levels, decreased C3 levels and high prevalence of LPV and sclerotic glomeruli were present in Cluster 3, and patients with late onset of the disease (median: 39.5 years) and near-normal C3 levels in Cluster 4. A significant difference was observed in the incidence of end-stage renal disease during follow-up between the different clusters. Patients in Clusters 3-4 had worse renal survival than patients in Clusters 1-2. ----- Conclusions: Our results confirm the main findings of the original cluster analysis and indicate that the observed, distinct pathogenic patterns are replicated in our cohort. Further investigations are necessary to analyse the distinct biological and pathogenic processes in these patient groups

C4 nephritic factor in patients with immune-complex-mediated membranoproliferative glomerulonephritis and C3-glomerulopathy

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Tubulointerstitialis nephritis és uveitis szindróma

A tubulointerstitialis nephritis és uveitis (TINU) szindróma ritka, aluldiagnosztizált oculorenalis szindróma, amelyet akut tubulointerstitialis nephritis és uveitis kialakulása jellemez. Az átlagos életkor a kialakuláskor 15 év, de bármely életkorban kialakulhat. Női predominancia áll fenn. Az uveitis jelentkezhet a tubulointerstitialis nephritis előtt, után és azzal egy időben. A klinikai tünetek típusosan nem specifikusak: láz, étvágytalanság, testsúlycsökkenés, hányinger és hányás, gyengeség, hasi fájdalom, ízületi és izomfájdalmak. A laboratóriumi vizsgálatok heveny vesefunkció-romlást, anaemiát, a gyulladásos paraméterek magasabb szintjét tárják fel. A vizeletvizsgálat eredményei tubulointerstitialis nephritisre jellemzőek: nem nephroticus proteinuria, steril leukocyturia, mikroszkópos haematuria és tubularis diszfunkció (például normoglykaemiás glycosuria) mutatható ki. A prognózis általában jó, különösen gyermekek esetében. Perzisztáló vesediszfunkció csak az esetek kis részében alakul ki. Közleményünkben egy 39 éves nőbeteg esetét mutatjuk be, és összefoglaljuk a TINU szindróma fő jellemzőit