Donor-derived membranous nephropathy in the allograft kidney: A rare but probably underestimated complication.

Transmitted donor-derived glomerular diseases in the allograft kidney are rare, especially when encountered in an allograft from a living donor. To date, only individual reports of donor-derived membranous nephropathy (MN) have been described. In this report, we present a case of MN discovered in a postreperfusion biopsy of a living-donor allograft. A follow-up biopsy 3 weeks later demonstrated persistent deposits. Thirteen months posttransplant, the recipient showed mildly worsening proteinuria but stable kidney function. To further our understanding of this exceedingly rare complication, we share our experience with 7 additional in-house cases together with 6 cases described in the literature to date. A minority of the donors were living. Most donors did not exhibit significant proteinuria illustrating how predonation screening could potentially miss donor-derived MN. Reactivity for phospholipase A2 receptor and thrombospondin type 1 domain containing 7A were negative in all stained cases. On follow-up, recipients variably exhibited slow resolution of the immune deposits, variable degrees of proteinuria (mainly subnephrotic), and no significant impairment of kidney function. Donor-derived MN is rare, phospholipase A2 receptor-negative, and can still be encountered in living donors despite rigorous screening. This report provides a brief examination of the pathology, clinical, and laboratory features of such patients involved.

Pathologic-genomic correlation identified a novel variant in FN1 and established the diagnosis of recurrent fibronectin glomerulopathy in the kidney allograft.

Fibronectin glomerulopathy is a rare inherited kidney disease, characterized by abnormal accumulation of fibronectin in the glomeruli. We report an exceptional case of recurrent fibronectin glomerulopathy first diagnosed in the kidney allograft. The presence of IgA staining in the native kidney biopsy and the reported family history of IgA nephropathy had led to initial pretransplant diagnosis of IgA nephropathy. At 4.5 years posttransplant, the patient presented with kidney insufficiency and minimal proteinuria. The allograft biopsy revealed glomerular deposits with very weak staining for immunoglobulins and vague filamentous material. Immunostaining for fibronectin was positive, and genetic studies showed a variant of unknown significance in the fibronectin 1 gene. Proteomic analyses of the glomeruli in the native kidney biopsy demonstrated large amount of fibronectin with abundant accumulation of the peptide synthesized by the detected variant. These findings established the diagnosis of recurrent fibronectin glomerulopathy secondary to a novel variant in the fibronectin 1 gene. This report sheds light on recurrent fibronectin glomerulopathy in the allograft, highlights the diagnostic pitfalls of the disease, and underscores the importance of pathologic-genomic correlation to establish the correct diagnosis.

The Banff 2022 Kidney Meeting Work Plan: Data-driven refinement of the Banff Classification for renal allografts.

The XVIth Banff Meeting for Allograft Pathology was held in Banff, Alberta, Canada, from September 19 to 23, 2022, as a joint meeting with the Canadian Society of Transplantation. In addition to a key focus on the impact of microvascular inflammation and biopsy-based transcript analysis on the Banff Classification, further sessions were devoted to other aspects of kidney transplant pathology, in particular T cell-mediated rejection, activity and chronicity indices, digital pathology, xenotransplantation, clinical trials, and surrogate endpoints. Although the output of these sessions has not led to any changes in the classification, the key role of Banff Working Groups in phrasing unanswered questions, and coordinating and disseminating results of investigations addressing these unanswered questions was emphasized. This paper summarizes the key Banff Meeting 2022 sessions not covered in the Banff Kidney Meeting 2022 Report paper and also provides an update on other Banff Working Group activities relevant to kidney allografts.

Banff 2022 Liver Group Meeting report: Monitoring long-term allograft health.

The Banff Working Group on Liver Allograft Pathology met in September 2022. Participants included hepatologists, surgeons, pathologists, immunologists, and histocompatibility specialists. Presentations and discussions focused on the evaluation of long-term allograft health, including noninvasive and tissue monitoring, immunosuppression optimization, and long-term structural changes. Potential revision of the rejection classification scheme to better accommodate and communicate late T cell-mediated rejection patterns and related structural changes, such as nodular regenerative hyperplasia, were discussed. Improved stratification of long-term maintenance immunosuppression to match the heterogeneity of patient settings will be central to improving long-term patient survival. Such personalized therapeutics are in turn contingent on a better understanding and monitoring of allograft status within a rational decision-making approach, likely to be facilitated in implementation with emerging decision-support tools. Proposed revisions to rejection classification emerging from the meeting include the incorporation of interface hepatitis and fibrosis staging. These will be opened to online testing, modified accordingly, and subject to consensus discussion leading up to the next Banff conference.

Association of Implantation Biopsy Findings in Living Donor Kidneys With Donor and Recipient Outcomes.

RATIONALE & OBJECTIVE: Some living donor kidneys are found to have biopsy evidence of chronic scarring and/or glomerular disease at implantation, but it is unclear if these biopsy findings help predict donor kidney recovery or allograft outcomes. Our objective was to identify the prevalence of chronic histological changes and glomerular disease in donor kidneys, and their association with donor and recipient outcomes. STUDY DESIGN: Retrospective cohort study. SETTING & PARTICIPANTS: Single center, living donor kidney transplants from January 2010 to July 2022. EXPOSURE: Chronic histological changes, glomerular disease in donor kidney implantation biopsies. OUTCOME: For donors, single-kidney estimated glomerular filtration rate (eGFR) increase, percent total eGFR loss, ≥40% eGFR decline from predonation baseline, and eGFR<60mL/min/1.73m2 at 6 months after donation; for recipients, death-censored allograft survival. ANALYTICAL APPROACH: Biopsies were classified as having possible glomerular disease by pathologist diagnosis or chronic changes based on the percentage of glomerulosclerosis, interstitial fibrosis/tubular atrophy, and vascular disease. We used logistic regression to identify factors associated with the presence of chronic changes, linear regression to identify the association between chronic changes and single-kidney estimated glomerular filtration rate (eGFR) recovery, and time-to-event analyses to identify the relationship between abnormal biopsy findings and allograft outcomes. RESULTS: Among 1,104 living donor kidneys, 155 (14%) had advanced chronic changes on implantation biopsy, and 12 (1%) had findings suggestive of possible donor glomerular disease. Adjusted logistic regression showed that age (odds ratio [OR], 2.44 per 10 years [95% CI, 1.98-3.01), Hispanic ethnicity (OR, 1.87 [95% CI, 1.15-3.05), and hypertension (OR, 1.92 [95% CI, 1.01-3.64), were associated with higher odds of chronic changes on implantation biopsy. Adjusted linear regression showed no association of advanced chronic changes with single-kidney eGFR increase or relative risk of eGFR<60mL/min/1.73m2. There were no differences in time-to-death-censored allograft failure in unadjusted or adjusted Cox proportional hazards models when comparing kidneys with chronic changes to kidneys without histological abnormalities. LIMITATIONS: Retrospective, absence of measured GFR. CONCLUSIONS: Approximately 1 in 7 living donor kidneys had chronic changes on implantation biopsy, primarily in the form of moderate vascular disease, and 1% had possible donor glomerular disease. Abnormal implantation biopsy findings were not significantly associated with 6-month donor eGFR outcomes or allograft survival. PLAIN-LANGUAGE SUMMARY: Kidney biopsies are the gold standard test to identify the presence or absence of kidney disease. However, kidneys donated by healthy living donors-who are extensively screened for any evidence of kidney disease before donation-occasionally show findings that might be considered "abnormal," including the presence of scarring in the kidney or findings suggestive of a primary kidney disease. We studied the frequency of abnormal kidney biopsy findings among living donors at our center. We found that about 14% of kidneys had chronic abnormalities and 1% had findings suggesting possible glomerular kidney disease, but the presence of abnormal biopsy findings was not associated with worse outcomes for the donors or their recipients.

The pathologic spectrum of adenovirus nephritis in the kidney allograft.

Adenovirus nephritis (ADVN) is a rare and understudied complication of kidney transplantation. Unlike BK virus nephropathy (BKVN), our knowledge of clinicopathologic manifestations of ADVN remains rudimentary and essentially limited to case reports. To expand on this, we retrospectively studied 11 kidney transplant recipients with ADVN and compared their allograft biopsies to 33 kidney transplant recipients with BKVN using conventional microscopy and the 770 gene Nanostring Banff Human Organ Transplant Profiling Panel. Patients with ADVN had a median age of 44 years, were predominantly male, and developed ADVN at a median of 31 months post-transplantation. Eight patients presented with fever and ten had hematuria. The most common histologic manifestations included granulomas (82%), tubulocentric inflammation (73%), and tubular degenerative changes consistent with acute tubular necrosis (73%). During a median follow-up of 55 months after biopsy, three patients developed allograft failure from subsequent acute rejection. All seven patients with available follow-up PCR showed resolution of viremia at a median of 30 days after diagnosis. Compared to BKVN, ADVN demonstrated more granulomas and less tubulointerstitial scarring. On follow-up, patients with ADVN had more rapid clearance of viral DNA from plasma. Transcriptomic analyses showed that ADVN had increased expression of several pro-inflammatory transcriptomes, mainly related to innate immunity, was associated with increased expression of transcripts with inhibitory effects on inflammatory response and showed higher enrichment with neutrophils, which can cause aggressive but short-lasting damage. Thus, we demonstrate that, despite its association with aggressive neutrophil-rich inflammation, ADVN does not often lead to allograft failure. Hence, preventing subsequent acute rejection following resolution of ADVN may improve allograft survival.

BK DNAemia and native kidney polyomavirus nephropathy following lung transplantation.

BK virus DNAemia (BKPyV) and nephropathy are common after kidney transplant; however, there are limited data on BK infections in nonrenal solid organ transplant recipients. We examined the frequency, clinical and pathologic features, and kidney and lung outcomes of BKPyV and BK virus native kidney nephropathy (BKVN) in lung transplant recipients at our center. Among 878 recipients transplanted from 2003 to 2019, 56 (6%) developed BKPyV at a median of 30.1 months after transplant (range, 0.6-213) and 11 (1.3%) developed BKVN at a median of 46 months after transplant (range, 9-213). The incidence of end-stage kidney disease was significantly higher in patients with peak viral load ≥10 000 copies/mL (39% vs 8%, P < .001). All cases of BKVN were in patients with peak viral load of ≥10 000 copies/mL, and 55% of these patients developed end-stage kidney disease. Despite the reduction of immunosuppression to treat BKVN, only 1 patient developed acute rejection, and lung function was stable >1 year. BKPyV and nephropathy are more common after lung transplantation than previously reported. Routine screening for BKPyV should be considered in all lung transplant recipients.

Proliferative Glomerulonephritis With Hidden Monotypic IgG3κ Deposits: A Case Report.

Rare cases of immunoglobulin G (IgG)-dominant immune complex-mediated glomerulonephritis demonstrate immunoglobulin subclass restriction without light chain restriction. Some of these cases may represent proliferative glomerulonephritis with monotypic immunoglobulin deposits (PGNMID) in which monotypic immunoglobulin is obscured by coexisting polytypic immunoglobulin. However, rigorous demonstration of this possibility is lacking to date. Here, we describe a case of IgG3-restricted immune complex-mediated glomerulonephritis without light chain restriction that apparently "transformed" into IgG3κ-PGNMID in a subsequent biopsy. We demonstrate, using several ancillary techniques, including use of the newly described antibodies directed against the conformational epitope at the junctions of heavy and light chains (HLC-IF), that the first biopsy likely represents IgG3κ-PGNMID in which monotypic IgG3κ was hidden by polytypic IgM. This case underscores the need to consider PGNMID in a differential diagnosis of IgG-dominant immune complex-mediated glomerulonephritis without light chain restriction and highlights the potential utility of IgG subclass staining and HLC-IF in such cases to detect monotypic immunoglobulin that may be obscured by coexisting IgM and/or IgA deposits.

CMV-associated collapsing focal segmental glomerulosclerosis after kidney transplant in a pediatric patient.

BACKGROUND: Cytomegalovirus (CMV) is a significant cause of morbidity among immunocompromised patients who have undergone kidney transplantation and is known to rarely induce collapsing focal segmental glomerulosclerosis (FSGS) among adults. METHODS: We present the first reported case of CMV-induced collapsing FSGS in a pediatric patient after kidney transplant. RESULTS: Our patient underwent a deceased donor kidney transplant due to end-stage renal disease secondary to lupus nephritis. Approximately 4 months after transplantation, he developed signs of worsening kidney function in the setting of CMV viremia and was found to have collapsing features of FSGS on kidney transplant biopsy. He was managed with a prompt escalation of antiviral therapy along with a reduction of immunosuppression and recovered without significant complication. At follow-up, he continued to have undetectable CMV titers, creatinine within normal limits, and no significant proteinuria. CONCLUSION: This report demonstrates CMV as a cause of collapsing FSGS and should be considered among pediatric transplant recipients who present with acute kidney injury, as should early assessment of APOL1 genetic status in both donor and recipient.

Endothelial TNF receptor 2 induces IRF1 transcription factor-dependent interferon-ß autocrine signaling to promote monocyte recruitment.

Endothelial-dependent mechanisms of mononuclear cell influx are not well understood. We showed that acute stimulation of murine microvascular endothelial cells expressing the tumor necrosis factor receptors TNFR1 and TNFR2 with the soluble cytokine TNF led to CXCR3 chemokine generation. The TNF receptors signaled through interferon regulatory factor-1 (IRF1) to induce interferon-ß (IFN-ß) and subsequent autocrine signaling via the type I IFN receptor and the transcription factor STAT1. Both TNFR2 and TNFR1 were required for IRF1-IFNß signaling and, in human endothelial cells TNFR2 expression alone induced IFN-ß signaling and monocyte recruitment. In vivo, TNFR1 was required for acute renal neutrophil and monocyte influx after systemic TNF treatment, whereas the TNFR2-IRF1-IFN-ß autocrine loop was essential only for macrophage accumulation. In a chronic model of proliferative nephritis, IRF1 and renal-expressed TNFR2 were essential for sustained macrophage accumulation. Thus, our data identify a pathway in endothelial cells that selectively recruits monocytes during a TNF-induced inflammatory response.

Longitudinal Outcomes of COVID-19-Associated Collapsing Glomerulopathy and Other Podocytopathies.

BACKGROUND: The long-term outcome of COVID-19-associated collapsing glomerulopathy is unknown. METHODS: We retrospectively identified 76 native kidney biopsies from patients with history of COVID-19 between March 2020 and April 2021. Presenting and outcome data were obtained for all 23 patients with collapsing glomerulopathy and for seven patients with noncollapsing podocytopathies. We performed APOL1 genotyping by Sanger sequencing, immunostaining for spike and nucleocapsid proteins, and in situ hybridization for SARS-CoV-2. RESULTS: The 23 patients with COVID-19-associated collapsing glomerulopathy were median age 57 years (range, 35-72), included 16 men, and were predominantly (91%) Black. Severity of COVID-19 was mild or moderate in most (77%) patients. All but one patient presented with AKI, 17 had nephrotic-range proteinuria, and six had nephrotic syndrome. Fourteen (61%) patients required dialysis at presentation. Among 17 patients genotyped, 16 (94%) were high-risk APOL1. Among 22 (96%) patients with median follow-up at 155 days (range, 30-412), 11 (50%) received treatment for COVID-19, and eight (36%) received glucocorticoid therapy for podocytopathy. At follow-up, 19 (86%) patients were alive, and 15 (68%) were dialysis free, including seven of 14 who initially required dialysis. The dialysis-free patients included 64% (seven of 11) of those treated for COVID-19 and 75% (six of eight) of those treated with glucocorticoids for podocytopathy. Overall, 36% achieved partial remission of proteinuria, 32% had no remission, and 32% reached combined end points of ESKD or death. Viral infection of the kidney was not detected. CONCLUSIONS: Half of 14 patients with COVID-19-associated collapsing glomerulopathy requiring dialysis achieved dialysis independence, but the long-term prognosis of residual proteinuric CKD remains guarded, indicating a need for more effective therapy.

Anti-neutrophil cytoplasmic antibody associated glomerulonephritis complicating treatment with hydralazine.

Hydralazine, a widely used therapy for hypertension and heart failure, can elicit autoimmune disease, including anti-neutrophil cytoplasmic antibody associated glomerulonephritis (ANCA-GN). We identified 80 cases of ANCA-GN complicating treatment with hydralazine, accounting for 4.3% (80/1858 biopsies) of ANCA-GN diagnosed between 2006 and 2019. Over three-fourths of patients were on hydralazine for at least one year, with mean daily dose of approximately 250 mg/day. ANCA testing revealed p-ANCA/myeloperoxidase-ANCA seropositivity in 98%, including 39% with dual p-ANCA/myeloperoxidase-ANCA and cANCA/anti-protinase 3-ANCA positivity, often accompanied by anti-nuclear antibody (89%), anti-histone antibody (98%), and hypocomplementemia (58%). Kidney biopsy revealed necrotizing and crescentic glomerulonephritis, similar to primary ANCA-GN, but significantly less frequently pauci-immune (77 vs. 100%) and more commonly associated with mesangial hypercellularity (30 vs. 5%), electron dense deposits (62 vs. 20%), and endothelial tubuloreticular inclusions (11 vs. 0%); all significant differences. On follow-up, 42 of 51 patients received induction immunosuppression: 19 reached the combined end-points of kidney failure or death and 32 had mean creatinine of 1.49 mg/dL at last follow-up. Thus, hydralazine-associated ANCA-GN often exhibits overlapping clinical and pathologic features of mild immune complex glomerulonephritis resembling lupus nephritis. With discontinuation of hydralazine and immunosuppression, outcomes are similar to primary ANCA-GN.

The clinicopathologic spectrum of segmental membranous glomerulopathy.

Membranous glomerulopathy (MGN) is characterized by global subepithelial immune deposits that stain most intensely by immunofluorescence for IgG. Here we describe the clinical and pathologic findings in a cohort of patients with MGN in which, by definition, only segmental immune deposits are present. This rare variant, termed segmental MGN (sMGN), is poorly characterized. We retrospectively identified all patients with sMGN diagnosed at Columbia University from January 2010 to October 2018, excluding those with systemic lupus erythematosus. Data on presenting features, pathologic findings, and outcomes were collected. Fifty cases of sMGN were identified, representing 2.5% of MGN. In 21 of 50 biopsies, there was an alternative, predominant disease process. The remaining 29 patients with isolated sMGN had a median creatinine of 0.97 mg/dl, median 24-hour urine protein 3.1 g/day, and 32% had nephrotic syndrome. Staining for NELL-1 (a protein kinase C binding protein) was positive in five of 17 cases. Staining for PLA2R, THSD7A, and exostosin 1 (autoantigens in primary MGN) was negative in all biopsies evaluated. Ultrastructural evaluation revealed predominantly early stage sMGN (stage 1 or 1-2 in 14/29). Follow-up was available for 21 of the 29 patients with isolated sMGN (median 12 months), including seven who received immunosuppression (primarily glucocorticoids). During follow-up, 86% had stable/improved kidney function and 45% achieved complete while 15% achieved partial remission. Among the 15 patients with isolated sMGN without full nephrotic syndrome, only two received immunosuppression; nonetheless, 50% achieved complete while 21% achieved partial remission. Thus, sMGN is a rare PLA2R-negative variant of MGN with 29% NELL-1 positivity and favorable prognosis, even in the absence of immunosuppressive treatment.

Kidney allograft biopsy findings after COVID-19.

COVID-19 has been associated with acute kidney injury and published reports of native kidney biopsies have reported diverse pathologies. Case series directed specifically to kidney allograft biopsy findings in the setting of COVID-19 are lacking. We evaluated 18 kidney transplant recipients who were infected with SARS-CoV-2 and underwent allograft biopsy. Patients had a median age of 55 years, six were female, and five were Black. Fifteen patients developed COVID-19 pneumonia, of which five required mechanical ventilation. Notably, five of 11 (45%) biopsies obtained within 1 month of positive SARS-CoV-2 PCR showed acute rejection (four with arteritis, three of which were not associated with reduced immunosuppression). The remaining six biopsies revealed podocytopathy (n = 2, collapsing glomerulopathy and lupus podocytopathy), acute tubular injury (n = 2), infarction (n = 1), and transplant glomerulopathy (n = 1). Biopsies performed >1 month after positive SARS-CoV-2 PCR revealed collapsing glomerulopathy (n = 1), acute tubular injury (n = 1), and nonspecific histologic findings (n = 5). No direct viral infection of the kidney allograft was detected by immunohistochemistry, in situ hybridization, or electron microscopy. On follow-up, two patients died and most patients showed persistent allograft dysfunction. In conclusion, we demonstrate diverse causes of kidney allograft dysfunction after COVID-19, the most common being acute rejection with arteritis.

The clinical significance of receiving a kidney allograft from deceased donor with chronic histologic changes.

Allograft survival of deceased donor kidneys with suboptimal histology (DRTx/suboptimal histology: >10% glomerulosclerosis, >10% tubulointerstitial scarring, or >mild vascular sclerosis) is inferior to both DRTx with optimal histology (DRTx/optimal histology) and living donor kidneys irrespective of histologic changes (LRTx). In this report, we explored the reasons behind this guarded outcome with a special focus on the role of alloimmunity. We initially assessed gene expression in 39 time-zero allograft biopsies using the Nanostring 770 genes PanCancer Immune Profiling Panel. Subsequently, we studied 696 consecutive adult kidney allograft recipients that were grouped according to allograft type and histology at time-zero biopsy [DRTx/suboptimal histology (n = 194), DRTx/optimal histology (n = 166), and LRTx (n = 336)]. Part-1: Several immune pathways were upregulated in time-zero biopsies from DRTx/suboptimal histology (n = 11) compared to LRTx (n = 17) but not to DRTx/optimal histology (n = 11). Part-2: Amongst the three groups of recipients, DRTx/suboptimal histology had the highest incidence of acute rejection episodes, most of which occurred during the first year after transplantation (early rejection). This increase was mainly attributed to T cell mediated rejection, while the incidence of antibody-mediated rejection was similar amongst the three groups. Importantly, early acute T cell mediated rejection was a strong independent predictor for allograft failure in DRTx/suboptimal histology (adjusted HR: 2.13, P = 0.005) but not in DRTx/optimal histology nor in LRTx. Our data highlight an increased baseline immunogenicity in DRTx/suboptimal histology compared to LRTx but not to DRTx/optimal histology. However, our results suggest that donor chronic histologic changes in DRTx may help transfer such increased baseline immunogenicity into clinically relevant acute rejection episodes that have detrimental effects on allograft survival. These findings may provide a rationale for enhanced immunosuppression in recipients of DRTx with baseline chronic histologic changes to minimize subsequent acute rejection and to prolong allograft survival.

A 2020 Banff Antibody-mediatedInjury Working Group examination of international practices for diagnosing antibody-mediated rejection in kidney transplantation - a cohort study.

The Banff antibody-mediated rejection (ABMR) classification is vulnerable to misinterpretation, but the reasons are unclear. To better understand this vulnerability, we evaluated how ABMR is diagnosed in practice. To do this, the Banff Antibody-Mediated Injury Workgroup electronically surveyed an international cohort of nephrologists/surgeons (n = 133) and renal pathologists (n = 99). Most providers (97%) responded that they use the Banff ABMR classification at least sometimes, but DSA information is often not readily available. Only 41.1% (55/133) of nephrologists/surgeons and 19.2% (19/99) of pathologists reported that they always have DSA results when the biopsy is available. Additionally, only 19.6% (26/133) of nephrologists/surgeons responded that non-HLA antibody or molecular transcripts are obtained when ABMR histologic features are present but DSA is undetected. Several respondents agreed that histologic features concerning for ABMR in the absence of DSA and/or C4d are not well accounted for in the current classification [31.3% (31/99) pathologists and 37.6% (50/133) nephrologist/surgeons]. The Banff ABMR classification appears widely accepted, but efforts to improve the accessibility of DSA information for the multidisciplinary care team are needed. Further clarity is also needed in Banff ABMR nomenclature to account for the spectrum of ABMR and for histologic features suspicious for ABMR when DSA is absent.

Postmortem Kidney Pathology Findings in Patients with COVID-19.

BACKGROUND: AKI is common among hospitalized patients with coronavirus disease 2019 (COVID-19) and is an independent risk factor for mortality. Although there are numerous potential mechanisms underlying COVID-19-associated AKI, our current knowledge of kidney pathologic findings in COVID-19 is limited. METHODS: We examined the postmortem kidneys from 42 patients who died of COVID-19. We reviewed light microscopy findings in all autopsies and performed immunofluorescence, electron microscopy, and in situ hybridization studies for SARS-CoV-2 on a subset of samples. RESULTS: The cohort had a median age of 71.5 years (range, 38-97 years); 69% were men, 57% were Hispanic, and 73% had a history of hypertension. Among patients with available data, AKI developed in 31 of 33 patients (94%), including 6 with AKI stage 1, 9 with stage 2, and 16 with stage 3. The predominant finding correlating with AKI was acute tubular injury. However, the degree of acute tubular injury was often less severe than predicted for the degree of AKI, suggesting a role for hemodynamic factors, such as aggressive fluid management. Background changes of hypertensive arterionephrosclerosis and diabetic glomerulosclerosis were frequent but typically mild. We identified focal kidney fibrin thrombi in 6 of 42 (14%) autopsies. A single Black patient had collapsing FSGS. Immunofluorescence and electron microscopy were largely unrevealing, and in situ hybridization for SARS-CoV-2 showed no definitive positivity. CONCLUSIONS: Among a cohort of 42 patients dying with COVID-19, autopsy histologic evaluation revealed acute tubular injury, which was typically mild relative to the degree of creatinine elevation. These findings suggest potential for reversibility upon resolution of SARS-CoV-2 infection.

Kidney Biopsy Findings in Patients with COVID-19.

BACKGROUND: Coronavirus disease 2019 (COVID-19) is thought to cause kidney injury by a variety of mechanisms. To date, pathologic analyses have been limited to patient reports and autopsy series. METHODS: We evaluated biopsy samples of native and allograft kidneys from patients with COVID-19 at a single center in New York City between March and June of 2020. We also used immunohistochemistry, in situ hybridization, and electron microscopy to examine this tissue for presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). RESULTS: The study group included 17 patients with COVID-19 (12 men, 12 black; median age of 54 years). Sixteen patients had comorbidities, including hypertension, obesity, diabetes, malignancy, or a kidney or heart allograft. Nine patients developed COVID-19 pneumonia. Fifteen patients (88%) presented with AKI; nine had nephrotic-range proteinuria. Among 14 patients with a native kidney biopsy, 5 were diagnosed with collapsing glomerulopathy, 1 was diagnosed with minimal change disease, 2 were diagnosed with membranous glomerulopathy, 1 was diagnosed with crescentic transformation of lupus nephritis, 1 was diagnosed with anti-GBM nephritis, and 4 were diagnosed with isolated acute tubular injury. The three allograft specimens showed grade 2A acute T cell-mediated rejection, cortical infarction, or acute tubular injury. Genotyping of three patients with collapsing glomerulopathy and the patient with minimal change disease revealed that all four patients had APOL1 high-risk gene variants. We found no definitive evidence of SARS-CoV-2 in kidney cells. Biopsy diagnosis informed treatment and prognosis in all patients. CONCLUSIONS: Patients with COVID-19 develop a wide spectrum of glomerular and tubular diseases. Our findings provide evidence against direct viral infection of the kidneys as the major pathomechanism for COVID-19-related kidney injury and implicate cytokine-mediated effects and heightened adaptive immune responses.

The spectrum of kidney biopsy findings in HIV-infected patients in the modern era.

HIV-associated kidney disease is evolving rapidly. Few North American studies have addressed modern trends and none has applied the 2018 Kidney Disease Improving Global Outcomes (KDIGO) pathologic classification. Therefore we performed a retrospective clinical-pathologic analysis of all HIV-positive patients with kidney biopsy interpreted at Columbia University from 2010-2018 using the KDIGO classification. The biopsy cohort of 437 HIV-positive patients had median age 53 years, including 66% males, 80% on anti-retroviral therapy, 57% with hypertension, 31% with diabetes, 27% with hepatitis C and 6% with hepatitis B co-infections. Race, known in 308 patients, included 58% black, 25% white and 17% Hispanic. Pathologic diagnoses were surprisingly diverse. Immune complex glomerulonephritis (ICGN) and diabetic nephropathy each outnumbered HIV-associated nephropathy, followed by tenofovir nephrotoxicity, FSGS- not otherwise specified (NOS) and global sclerosis (NOS). HIV-associated nephropathy was the most common disease in patients not on anti-retroviral therapy, and 94% were black. The association of FSGS (NOS) with black race (68%) and anti-retroviral therapy use (77%) suggests some cases may represent attenuated HIV-associated nephropathy. The most common ICGNs were IgA nephropathy and membranous glomerulopathy, both associating with anti-retroviral therapy (over 90%), followed by hepatitis C-associated proliferative ICGN. Among the 16 cases of uncharacterized ICGN lacking identifiable etiology, 69% were not on anti-retroviral therapy, possibly representing true HIV-associated immune complex kidney disease. Dual diseases occurred in 17% of patients, underscoring lesion complexity. Thus, anti-retroviral therapy has shifted the landscape of HIV-associated kidney disease toward diverse ICGN, diabetic nephropathy, and non-collapsing glomerulosclerosis, but has not eradicated HIV-associated nephropathy.

Association of HLA Typing and Alloimmunity With Posttransplantation Membranous Nephropathy: A Multicenter Case Series.

RATIONALE & OBJECTIVES: Posttransplantation membranous nephropathy (MN) represents a rare complication of kidney transplantation that can be classified as recurrent or de novo. The clinical, pathologic, and immunogenetic characteristics of posttransplantation MN and the differences between de novo and recurrent MN are not well understood. STUDY DESIGN: Multicenter case series. SETTING & PARTICIPANTS: We included 77 patients from 5 North American and European medical centers with post-kidney transplantation MN (27 de novo and 50 recurrent). Patients with MN in the native kidney who received kidney allografts but did not develop recurrent MN were used as nonrecurrent controls (n = 43). To improve understanding of posttransplantation MN, we compared de novo MN with recurrent MN and then contrasted recurrent MN with nonrecurrent controls. FINDINGS: Compared with recurrent MN, de novo MN was less likely to be classified as primary MN (OR, 0.04; P < 0.001) and had more concurrent antibody-mediated rejection (OR, 12.0; P < 0.001) and inferior allograft survival (HR for allograft failure, 3.2; P = 0.007). HLA-DQ2 and HLA-DR17 antigens were more common in recipients with recurrent MN compared with those with de novo MN; however, the frequency of these recipient antigens in recurrent MN was similar to that in nonrecurrent MN controls. Among the 93 kidney transplant recipients with native kidney failure attributed to MN, older recipient age (HR per each year older, 1.03; P = 0.02), recipient HLA-A3 antigen (HR, 2.5; P = 0.003), steroid-free immunosuppressive regimens (HR, 2.84; P < 0.001), and living related allograft (HR, 1.94; P = 0.03) were predictors of MN recurrence. LIMITATIONS: Retrospective case series, limited sample size due to rarity of the disease, nonstandardized nature of data collection and biopsies. CONCLUSIONS: De novo and recurrent MN likely represent separate diseases. De novo MN is associated with humoral alloimmunity and guarded outcome. Potential predisposing factors for recurrent MN include recipients who are older, recipient HLA-A3 antigen, steroid-free immunosuppressive regimen, and living related donor kidney.