C3 glomerulonephritis associated with ANCA positivity: a case report

Background C3 glomerulopathy (C3G) is a recent disease classification that is characterized by the presence of glomerular deposits (composed of C3) in the absence of significant amounts of immunoglobulin and comprises dense deposit disease and C3 glomerulonephritis (C3GN). Most C3GN manifests as membranoproliferative, mesangial proliferative glomerulonephritis patterns via light microscopy. Pure membranous nephropathy (MN)-like glomerular lesions are rare manifestations of C3GN. Anti-neutrophil cytoplasmic antibodies (ANCAs) are also seldomly reported to be positive in C3GN. Herein, we report the case of a C3GN patient presenting with an MN-like glomerular pattern with ANCA positivity. Case presentation A 68-year-old woman was admitted to a local hospital with elevated serum creatinine for two weeks. Laboratory tests showed a hemoglobin level of 85 g/L. Urinalysis was positive for 2 + protein and 360 RBCs/HPF. Blood biochemistry analysis revealed the following concentrations: albumin, 30.3 g/L; globulin, 46.2 g/L; blood urea nitrogen, 19.9 mmol/L; and serum creatinine, 234 µmol/L. The serum C3 level was 0.4950 g/L, and the serum C4 level was 0.1050 g/L. The direct Coombs test was positive. Serologic testing for ANCA revealed the presence of p-ANCA (1:10) by indirect immunofluorescence microscopy assay, as well as the presence of PR3 1.2 (normal range < 1) and MPO 3.5 (normal range < 1) by enzyme immunoassay. Renal biopsy sample pathology showed 2/6 cellular crescents and thickened glomerular basement membranes. Immunofluorescence testing revealed only diffuse, finely granular depositions of C3 along the glomerular capillary walls in frozen and paraffin-embedded tissue sections. Electron microscopy demonstrated the presence of subepithelial electron-dense deposits, similar to those that are observed in membranous nephropathy. Corticosteroid and cyclophosphamide were administered, with a subsequent improvement in renal function. Conclusions We present the rare case of a patient with MN-like C3GN with ANCA positivity. C3GN with ANCA positivity may be represented by more crescents, severe renal dysfunction and more extrarenal manifestations. More cases are needed to elucidate the clinicopathologic features and optimal treatments of these patients.

Neural Epidermal Growth Factor–Like 1 Protein–Positive Membranous Nephropathy in Chinese Patients

Background and objectivesThe neural EGF-like 1 (NELL-1) protein is a novel antigen in primary membranous nephropathy. The prevalence and clinical characteristics of NELL-1–positive membranous nephropathy in Chinese individuals with primary membranous nephropathy are unclear.Design, setting, participants, & measurementsA total of 832 consecutive patients with biopsy-proven primary membranous nephropathy were enrolled. The glomerular expression of phospholipase A2 receptor (PLA2R) and thrombospondin type 1 domain-containing 7A (THSD7A) was screened. Glomerular immunohistochemistry staining for NELL-1 was performed in 43 patients with PLA2R- and THSD7A-negative membranous nephropathy, 31 patients with PLA2R-positive membranous nephropathy, and two patients with PLA2R and THSD7A double positivity. The NELL-1 antibody was also detected in the sera of patients with NELL-1–positive membranous nephropathy by western blot. Clinical and pathologic features were comparable between patients with isolated NELL-1–positive, isolated PLA2R/THSD7A-positive, and triple antigen–negative membranous nephropathy.ResultsAmong the 832 patients with primary membranous nephropathy, 11 of 54 (20%) patients with PLA2R-negative membranous nephropathy had THSD7A-positive membranous nephropathy. NELL-1–positive membranous nephropathy accounted for 35% (15 of 43) of all patients with PLA2R- and THSD7A-negative membranous nephropathy. One patient was double positive for NELL-1 and PLA2R in glomerular deposits and positive for only the PLA2R antibody in the serum. Most patients with NELL-1–positive membranous nephropathy were women. No tumors were found. There were significant differences in the prevalence of IgG subtypes between patients with different antigen positivity. Among patients with isolated NELL-1–positive membranous nephropathy, although 80% (12 of 15) were IgG4 staining positive, the proportion of IgG4 dominance was only 67% (ten of 15).ConclusionsAbout one third of patients who were PLA2R and THSD7A negative were NELL-1 positive in Chinese patients with primary membranous nephropathy. NELL-1–positive membranous nephropathy was more common than THSD7A-positive membranous nephropathy in PLA2R-negative membranous nephropathy.

Fibrillary glomerulonephritis or complement 3 glomerulopathy: a rare case of diffuse necrotising crescentic glomerulonephritis with C3-dominant glomerular deposition and positive DNAJB9

Fibrillary glomerulonephritis (FGN) and complement 3 glomerulopathy (C3G) are rare forms of glomerulonephritis with distinct aetiologies. Both FGN and C3G can present with nephritic syndrome. FGN is associated with autoimmune disease, dysproteinaemia, malignancy and hepatitis C infection. C3G is caused by the unregulated activation of the alternative complement pathway. We present a rare case of diffuse necrotising crescentic glomerulonephritis with dominant C3 glomerular staining on immunofluorescence—consistent with C3G—but electron microscopy (EM) findings of randomly oriented fibrils with a mean diameter of 14 nm and positive immunohistochemistry for DNAJB9—suggestive of FGN. To the best of our knowledge, this is the first reported case of FGN to show dominant C3 glomerular deposits. This case report reaffirms the utility of EM in the evaluation of nephritic syndrome and highlights the value of DNAJB9—a novel biomarker with a sensitivity and specificity near 100% for FGN.

Seropositive PLA2R-associated membranous nephropathy but biopsy-negative PLA2R staining

Background Serum phospholipase A2 receptor (PLA2R) antibody (SAb) and glomerular deposits of PLA2R antigen (GAg) have been tested widely in idiopathic membranous nephropathy (MN). Recently, we noticed a special form of PLA2R-associated MN with positive circulating PLA2R antibody but negative PLA2R deposits in the glomeruli by immunofluorescence on frozen tissue (IF-F). The significance of this form of PLA2R-associated MN is yet to be elucidated. This study aimed to explore the clinicopathological features of these PLA2R-associated MN patients. Methods This study enrolled 229 biopsy-proven PLA2R-associated MN patients with SAb+. SAb was measured by enzyme-linked immunosorbent assay, and GAg was detected by IF-F. These patients were divided into SAb+/GAg+ and SAb+/GAg− groups. Clinicopathological characteristics of SAb+/GAg+ and SAb+/GAg− PLA2R-associated MN patients were compared. PLA2R antigens of 19 SAb+/GAg− PLA2R-associated MN patients were verified by immunohistochemistry on paraffin tissue (IHC-P). Results Among 229 SAb+ PLA2R-associated MN patients, 210 (91.70%) were GAg+ and 19 (8.3%) were GAg−. These 19 SAb+/GAg− PLA2R-associated MN patients presented positive PLA2R deposits by IHC-P. Compared with SAb+/GAg+ PLA2R-associated MN patients, SAb+/GAg- PLA2R-associated MN patients had higher levels of serum PLA2R antibody (P = 0.004), increased proteinuria (P = 0.008), lower serum albumin (P = 0.019), more prominent chronic pathological lesions in terms of glomerulosclerosis score (P = 0.025), interstitial fibrosis score (P = 0.016), tubular atrophy score (P = 0.010) and total renal chronicity score (P = 0.010), and were more likely to be accompanied by focal segmental glomerulosclerosis (P = 0.014). Higher SAb level was associated with the total renal chronicity score (odds ratio per 100 RU/mL, 1.16; 95% confidence interval 1.01–1.33; P = 0.033). Conclusions PLA2R-associated MN patients with seropositive PLA2R antibody but negative PLA2R deposits in the glomeruli by IF-F have higher levels of SAb and worse clinicopathological manifestations compared with their double-positive counterparts. IHC-P can be an alternative technique to reveal PLA2R glomerular deposits.

Evaluation of the Classification Accuracy of the Kidney Biopsy Direct Immunofluorescence through Convolutional Neural Networks

Background and objectivesImmunohistopathology is an essential technique in the diagnostic workflow of a kidney biopsy. Deep learning is an effective tool in the elaboration of medical imaging. We wanted to evaluate the role of a convolutional neural network as a support tool for kidney immunofluorescence reporting.Design, setting, participants, & measurementsHigh-magnification (×400) immunofluorescence images of kidney biopsies performed from the year 2001 to 2018 were collected. The report, adopted at the Division of Nephrology of the AOU Policlinico di Modena, describes the specimen in terms of “appearance,” “distribution,” “location,” and “intensity” of the glomerular deposits identified with fluorescent antibodies against IgG, IgA, IgM, C1q and C3 complement fractions, fibrinogen, and κ- and λ-light chains. The report was used as ground truth for the training of the convolutional neural networks.ResultsIn total, 12,259 immunofluorescence images of 2542 subjects undergoing kidney biopsy were collected. The test set analysis showed accuracy values between 0.79 (“irregular capillary wall” feature) and 0.94 (“fine granular” feature). The agreement test of the results obtained by the convolutional neural networks with respect to the ground truth showed similar values to three pathologists of our center. Convolutional neural networks were 117 times faster than human evaluators in analyzing 180 test images. A web platform, where it is possible to upload digitized images of immunofluorescence specimens, is available to evaluate the potential of our approach.ConclusionsThe data showed that the accuracy of convolutional neural networks is comparable with that of pathologists experienced in the field.

Galactose-Deficient IgA1 Deposits in Clear Cell Renal Cell Carcinoma-Related Henoch–Schönlein Purpura Nephritis

Recent studies suggest that galactose-deficient IgA1 (Gd-IgA1) plays a role in the pathogenesis of primary IgA nephropathy (IgAN) and Henoch–Schönlein purpura nephritis (HSPN). Furthermore, immunostaining of KM55, an antibody that identifies Gd-IgA1, may be helpful to differentiate primary IgAN and HSPN from secondary causes of glomerular IgA deposition. We report sequential kidney biopsies of a malignancy-associated HSPN, showing intense glomerular mesangial IgA deposition at the initial kidney biopsy and dramatic decrease in disappearance of glomerular deposits after tumor removal. We demonstrate that the glomerular IgA deposition contains Gd-IgA1, detected by immunostaining of KM55, with similar distribution and intensity to IgA. This suggests that renal Gd-IgA1 deposition may play a role in the pathogenesis of malignancy-associated HSPN.

P0424CLINICO-PATHOLOGICAL CHARACTERISTICS AND OUTCOMES OF PATIENTS WITH DNAJB9 POSITIVE FIBRILLARY GLOMERULONEPHRITIS

Background and Aims To investigate the clinicopathological features and prognosis of DNAJB9 positive fibrillary glomerulonephritis (FGN) in a single center in China. Method Cases diagnosed as FGN by renal biopsy from January 2011 to December 2019 in Jinling Hospital were stained with anti-DNAJB9 by immunohistochemistry. The patients with DNAJB9 positive FGN were retrospective analyzed. Results DNAJB9 staining of glomerular deposits was seen in 6 cases of FGN. 1 man and 5 women with a median age of 26 years (range, 21 to 49 years) were studied. Underlying autoimmune disease of Sjogren's syndrome and Hashimoto thyroiditis was in 1 case. None of them had dysproteinemia, malignancy, hepatitis C, hepatitis B, cryoglobulinemia, or diabetes. The patients presented with hypertension and edema in 5 cases, renal insufficiency in 1 case, and proteinuria in 6 cases with the median 24-hour urine protein 2.58 g (range, 1.66 to 9.57 g), nephrotic syndrome in 3 cases, and microscopic hematuria in 2 cases. The histologic pattern was mesangial proliferative glomerulonephritis (GN) and membranoproliferative GN. A mean of 9.7% of glomeruli were globally sclerotic. Crescents were present in 1 case (10%). The degree of tubular atrophy and interstitial fibrosis were absent (2 cases) and mild (4 cases), and severe acute tubular injury was in 1 case. All 6 cases showed glomerular positivity for IgG, C3 and C1q, 5 of which were positive for IgM, and 4 of which were positive for IgA. The glomerular deposits stained for polyclonal IgG subclasses and both kappa and lambda light chains in 3 cases. In 1 case, it stained for polyclonal IgG subclasses without kappa or lambda. IgG subclasses were IgG4 dominant in 3 cases and IgG1 dominant in 1 case. In 2 cases, they stained for monoclonal IgG1-kappa and IgG1-lambda. On electron microscopy (EM), the fibrillary deposits were seen infiltrating the mesangium, subendothelial, subepithelial area in all 6 cases, and the lamina densa of the GBMs in 5 cases with diameter of 7-40nm. Combined with observation of DNAJB9 staining, immunofluorescence microscopy and EM, extraglomerular deposits were identified in vessel walls in 5 cases, tubular basement membranes in 3 cases, peritubular capillaries in 3 cases. Congo red positivity was in 4 cases. At a median time of 32.9 months (range, 1 to 68.3 months) after biopsy, 3 cases were stable, 1 case had partial renal function recovery, and 2 cases had partial remission of proteinuria. Conclusion DNAJB9 immunohistochemistry is sensitive and specific for FGN. Monoclonal IgG and light chain was observed in young patients. Extraglomerular deposits were common. Prognosis was good in this young patient’s series.

P56 A rare case of Sjögren's nephropathy

Background A presentation of acute kidney injury (AKI) in a patient with a longstanding diagnosis of SLE nephritis was challenged following unexpected renal biopsy and immunology resulting in a diagnosis of primary Sjögren's Syndrome (pSS) related fibrillary glomerulonephritis (FGN). Methods A 62 year old Caucasian female presented with AKI and infected leg ulcer. Previously diagnosed with SLE (1996), anti-phospholipid syndrome and non-biopsy proven lupus nephritis (LN), CKD stage G2/3 she was on Hydroxychloroquine and lifelong anticoagulation. Examination revealed bilateral pitting oedema up to knees and a large non healing skin ulcer to left knee. Investigations showed new anaemia (Hb 75g/dl, MCV 94), lymphopaenia, urea- 25 (9.8), Creatinine- 280 (97), urine protein 6.88g/24 hr. USS KUB, ECHO, CXR, virology screen, PET CT were unremarkable. Immunology studies revealed ANA 1:160, anti-Ro, anti-La, but normal DsDNA and C3, C4. In the light of reported sicca symptoms and serology the diagnosis was revised to pSS. Renal biopsy was initially reported as diffuse lupus nephritis (Class IV) with crescents, and focal weak mesangial IgG and C3 but no glomerular deposits. Electron microscopy (EM) demonstrated abundant mesangial and intramembranous deposits with a fibrillary substructure diagnostic of FGN. Immunosuppression with pulsed intravenous (IV) methylprednisolone and IV Cyclophosphamide were given. She developed acute arterial intercostal bleeding at biopsy site and further significant lower gastrointestinal bleeding unamenable to endoscopic therapy or embolisation and the patient died. Results This case highlights the importance of ensuring that serology is interpreted correctly alongside histopathology and urinalysis in the diagnosis of CTD related renal disease. PSS related nephropathy is seen in less than 10% of patients. Tubulointerstitial nephritis (TIN) accounts for 2/3 of patients and glomerulonephritis (GN), typically membranoproliferative GN (MPGN) for most others. FGN in pSS is very rare, with only 3 reported cases to date. Like lupus nephritis, FGN can present with AKI, hypertension and nephrotic range proteinuria. However, renal biopsy proves invaluable in differentiating between the conditions. In FGN characteristically on biopsy disorganised, non-branching fibrils are seen in all glomerular compartments and are negative for congo red stain further differentiating from amyloid FGN. Immunofluorescence microscopy shows uniform staining of the fibrils for immunoglobulins (mostly subclass IgG4). FGN has a poor prognosis with patients developing severe chronic renal failure despite immunosuppression. Conclusion Considering surprising investigation results, it is crucial we rechallenge the validity of longstanding diagnoses as highlighted by our case. In proven pSS with systemic features we recommend screening all patients for renal disease annually including serum electrolytes, urine dipstick, protein creatinine ratio and pH. If abnormalities are identified, renal US and consideration of biopsy is crucial in establishing aetiology as management and prognosis differs between subtypes. Disclosures C. Amoasii None. R. Benson None. J. Harper None. D. Mewar None.