Molecular diagnosis of antibody-mediated rejection: Evaluating biopsy-based transcript diagnostics in the presence of donor-specific antibodies but without microvascular inflammation, a single-center descriptive analysis

Biopsy-based transcript diagnostics may identify molecular antibody-mediated rejection (AMR) when microvascular inflammation (MVI) is absent. In this single-center cohort, biopsy-based transcript diagnostics were validated in 326 kidney allograft biopsies. A total of 71 histological AMR and 35 T cell-mediated rejection (TCMR) cases were identified as molecular AMR and TCMR in 55% and 63%, respectively. Among 121 cases without MVI (glomerulitis + peritubular capillaritis = 0), 45 (37%) donor-specific antibody (DSA)-positive and 76 (63%) DSA-negative cases were analyzed. Twenty-one out of the 121 (17%) cases showed borderline changes, or TCMR, while BK nephropathy was excluded. None of the 45 DSA-positive patients showed molecular AMR. Among 76 DSA-negative patients, 2 had mixed molecular AMR/TCMR. All-AMR phenotype scores (sum of R4-R6) exhibited median values of 0.13 and 0.12 for DSA-positive and DSA-negative patients, respectively (P = .84). A total of 13% (6/45) DSA-positive and 11% (8/76) DSA-negative patients showed an all-AMR phenotype score > 0.30 (P = .77). Patients with a higher all-AMR phenotype score showed 33% more histologic TCMR (P = .005). The median all-AMR phenotype scores of glomerular basement membrane double contours = 0 and glomerular basement membrane double contours > 0 biopsies were 0.12 and 0.10, respectively (P = .35). Biopsy-based transcript diagnostics did not identify molecular AMR in cases without MVI. Follow-up biopsies and outcome data should evaluate the clinical relevance of subthreshold molecular alterations.

Neurologic involvement in cystinosis: Focus on brain lesions and new evidence of four-repeat (4R-) Tau immunoreactivity

Nephropathic cystinosis is a rare autosomal recessive storage disorder caused by CTNS gene mutations, leading to autophagy-lysosomal pathway impairment and cystine crystals accumulation. Neurologic involvement is highly variable and includes both neurodevelopmental and neurodegenerative disturbances, as well as focal neurologic deficits. By presenting longitudinal data of a 28-year-old patient with a large infratentorial lesion, we summarized the pathology, clinical and imaging features of neurological involvement in cystinosis patients. Brain damage in form of cystinosis-related cerebral lesions occurs in advanced disease phases and is characterized by the accumulation of cystine crystals, subsequent inflammation with vasculitis-like features, necrosis, and calcification. Epilepsy is a frequent comorbidity in affected individuals. Steroids might play a role in the symptomatic treatment of "stroke-like" episodes due to edematous-inflammatory lesions, but probably do not change the overall prognosis. Lifelong compliance to depleting therapy with cysteamine still represents the main therapeutic option. However, consequences of CTNS gene defects are not restricted to cystine accumulation. New evidence of four-repeat (4R-) Tau immunoreactivity suggests concurrent progressive neurodegeneration in cystinosis patients, highlighting the need of innovative therapeutic strategies, and shedding light on the crosstalk between proteinopathies and autophagy-lysosomal system defects. Eventually, emerging easily accessible biomarkers such as serum neurofilament light chains (NfL) might detect subclinical neurologic involvement in cystinosis patients.

Impact of kidney biopsy on deciding when to initiate enzyme replacement therapy in children with Fabry disease

BACKGROUND

Recommendations on when to start enzyme replacement therapy (ERT) in children with Fabry disease (FD) differ between guidelines. In this study, kidney biopsies of a cohort of 14 untreated children and one treated child were analyzed for their morphologic changes to determine whether early initiation of ERT is indicated.

METHODS

All pediatric FD patients (< 18 years old) diagnosed between 2003 and 2021 in our department who received a kidney biopsy were enrolled. Clinical symptoms; laboratory parameters regarding kidney function, such as eGFR, plasma urea, protein-creatinine, and albumin/creatinine ratio; and 14 kidney biopsies prior to ERT and one under treatment were retrospectively analyzed.

RESULTS

A total of 14 patients were enrolled, including 9 male and 5 female children, aged 3-18 years (median age 11). Seven of the enrolled children were 10 years old or younger. Histological analysis of kidney biopsy samples revealed severe vacuolization and accumulation of inclusions in podocytes and renal tubules. The majority of cases had no FD-specific clinical or laboratory features independent of age, gender, or genotype. The youngest FD patient presenting with isolated abnormal kidney biopsy was 3 years old.

CONCLUSIONS

We demonstrate that histological lesions, typical for FD, can be observed in kidney biopsies at a very young age in patients without classical clinical symptoms or laboratory abnormalities. Thus, we recommend kidney biopsies as a possible tool for early diagnosis of renal involvement in FD. As a consequence of these early biopsy findings without a clinical correlate, an early initiation of ERT should be considered. A higher resolution version of the Graphical abstract is available as Supplementary information.

Systems analyses of the Fabry kidney transcriptome and its response to enzyme replacement therapy identified and cross-validated enzyme replacement therapy-resistant targets amenable to drug repurposing

Fabry disease is a rare disorder caused by variations in the alpha-galactosidase gene. To a degree, Fabry disease is manageable via enzyme replacement therapy (ERT). By understanding the molecular basis of Fabry nephropathy (FN) and ERT's long-term impact, here we aimed to provide a framework for selection of potential disease biomarkers and drug targets. We obtained biopsies from eight control individuals and two independent FN cohorts comprising 16 individuals taken prior to and after up to ten years of ERT, and performed RNAseq analysis. Combining pathway-centered analyses with network-science allowed computation of transcriptional landscapes from four nephron compartments and their integration with existing proteome and drug-target interactome data. Comparing these transcriptional landscapes revealed high inter-cohort heterogeneity. Kidney compartment transcriptional landscapes comprehensively reflected differences in FN cohort characteristics. With exception of a few aspects, in particular arteries, early ERT in patients with classical Fabry could lastingly revert FN gene expression patterns to closely match that of control individuals. Pathways nonetheless consistently altered in both FN cohorts pre-ERT were mostly in glomeruli and arteries and related to the same biological themes. While keratinization-related processes in glomeruli were sensitive to ERT, a majority of alterations, such as transporter activity and responses to stimuli, remained dysregulated or reemerged despite ERT. Inferring an ERT-resistant genetic module of expressed genes identified 69 drugs for potential repurposing matching the proteins encoded by 12 genes. Thus, we identified and cross-validated ERT-resistant gene product modules that, when leveraged with external data, allowed estimating their suitability as biomarkers to potentially track disease course or treatment efficacy and potential targets for adjunct pharmaceutical treatment.

[Basic nephropathology for pathologists-part 2 : Non-inflammatory lesions]

The evaluation of kidney biopsies for specific renal diseases or kidney transplant biopsies is mainly restricted to specialized centers. Lesions in nonneoplastic renal tissue in partial nephrectomies or nephrectomies due to renal tumors, especially noninflammatory, ischemic, vascular changes or diabetic nephropathy can be of greater prognostic significance than the tumor itself in patients with a localized tumor and good tumor-associated survival. In this part of basic nephropathology for pathologists, the most common noninflammatory lesions of the vascular, glomerular and tubulo-interstitial compartment are discussed.

Transbronchial Cryobiopsy Compared to Forceps Biopsy for Diagnosis of Acute Cellular Rejection in Lung Transplants: Analysis of 63 Consecutive Procedures

Background: Acute cellular rejection (ACR) is a complication after lung transplantation (LTx). The diagnosis of ACR is based on histologic findings using transbronchial forceps biopsy (FB). However, its diagnostic accuracy is limited because of the small biopsy size and crush artifacts. Transbronchial cryobiopsy (CB) provides a larger tissue size compared with FB. Methods: FB and CB were obtained consecutively during the same bronchoscopy (February 2020–April 2021). All biopsies were scored according to the ISHLT criteria by three pathologists. Interobserver agreement was scored by the kappa index. We assessed the severity of bleeding and the presence of pneumothorax. Results: In total, 35 lung transplant recipients were included, and 126 CBs and 315 FBs were performed in 63 consecutive bronchoscopies. ACR (A1–A3, minimal–moderate) was detected in 18 cases (28.6%) by CB, whereas ACR was detected in 3 cases (4.8%) by FB. Moderate and severe bleeding complicated FB and CB procedures in 23 cases (36.5%) and 1 case (1.6%), respectively. Pneumothorax occurred in 6.3% of patients. The interobserver agreement was comparable for both CB and FB. Conclusions: CB provided an improved diagnostic yield for ACR diagnosis, leading to reclassification and changes in treatment strategies in 28.6% of cases. Prospective studies should better define the role of CB after LTx.

[Basic nephropathology for pathologists-part 1 : Kidney biopsy-inflammation and immune complexes]

The assessment of kidney biopsies is mainly confined to specialized centres. However, sometimes a kidney biopsy is submitted to a general pathologist, and in addition peritumorous renal parenchyma in tumour nephrectomies can have concomitant non-neoplastic renal disease. Here we present a survey of inflammatory and immunologic changes in all renal compartments, which may in part indicate the need of prompt therapeutic intervention such as in vasculitis, glomerulonephritis and interstitial nephritis. It is important to take into account that renal involvement of vasculitis is mainly centred in glomeruli and only to a much lesser extent in arteries, and that the frequently observed interstitial inflammation very often is an epiphenomenon of another primary kidney disease and not an independent disease process. Typical renal patterns of injury are emphasised.

Histologic and Molecular Patterns in Responders and Non-responders With Chronic-Active Antibody-Mediated Rejection in Kidney Transplants

Introduction

There is no proven therapy for chronic-active antibody-mediated rejection (caABMR), the major cause of late kidney allograft failure. Histological and molecular patterns associated with possible therapy responsiveness are not known.

Methods

Based on rigorous selection criteria this single center, retrospective study identified 16 out of 1027 consecutive kidney transplant biopsies taken between 2008 and 2016 with pure, unquestionable caABMR, without other pathologic features. The change in estimated GFR pre- and post-biopsy/treatment were utilized to differentiate subjects into responders and non-responders. Gene sets reflecting active immune processes of caABMR were defined a priori, including endothelial, inflammatory, cellular, interferon gamma (IFNg) and calcineurin inhibitor (CNI) related-genes based on the literature. Transcript measurements were performed in RNA extracted from stored, formalin-fixed, paraffin-embedded (FFPE) samples using NanoString™ technology. Histology and gene expression patterns of responders and non-responders were compared.

Results

A reductionist approach applying very tight criteria to identify caABMR and treatment response excluded the vast majority of clinical ABMR cases. Only 16 out of 139 cases with a written diagnosis of chronic rejection fulfilled the caABMR criteria. Histological associations with therapy response included a lower peritubular capillaritis score (p = 0.028) along with less glomerulitis. In contrast, no single gene discriminated responders from non-responders. Activated genes associated with NK cells and endothelial cells suggested lack of treatment response.

Conclusion

In caABMR active microvascular injury, in particular peritubular capillaritis, differentiates treatment responders from non-responders. Transcriptome changes in NK cell and endothelial cell associated genes may further help to identify treatment response. Future prospective studies will be needed which include more subjects, who receive standardized treatment protocols to identify biomarkers for treatment response.

Clinical Trial Registration

[ClinicalTrials.gov], identifier [NCT03430414].

Successful Induction of Specific Immunological Tolerance by Combined Kidney and Hematopoietic Stem Cell Transplantation in HLA-Identical Siblings

Induction of immunological tolerance has been the holy grail of transplantation immunology for decades. The only successful approach to achieve it in patients has been a combined kidney and hematopoietic stem cell transplantation from an HLA-matched or -mismatched living donor. Here, we report the first three patients in Europe included in a clinical trial aiming at the induction of tolerance by mixed lymphohematopoietic chimerism after kidney transplantation. Two female and one male patient were transplanted with a kidney and peripherally mobilized hematopoietic stem cells from their HLA-identical sibling donor. The protocol followed previous studies at Stanford University: kidney transplantation was performed on day 0 including induction with anti-thymocyte globulin followed by conditioning with 10x 1.2 Gy total lymphoid irradiation and the transfusion of CD34+ cells together with a body weight-adjusted dose of donor T cells on day 11. Immunosuppression consisted of cyclosporine A and steroids for 10 days, cyclosporine A and mycophenolate mofetil for 1 month, and then cyclosporine A monotherapy with tapering over 9–20 months. The 3 patients have been off immunosuppression for 4 years, 19 months and 8 months, respectively. No rejection or graft-versus-host disease occurred. Hematological donor chimerism was stable in the first, but slowly declining in the other two patients. A molecular microscope analysis in patient 2 revealed the genetic profile of a normal kidney. No relevant infections were observed, and the quality of life in all three patients is excellent. During the SARS-CoV-2 pandemic, all three patients were vaccinated with the mRNA vaccine BNT162b2 (Comirnaty^®), and they showed excellent humoral and in 2 out 3 patients also cellular SARS-CoV-2-specific immunity. Thus, combined kidney and hematopoietic stem cell transplantation is a feasible and successful approach to induce specific immunological tolerance in the setting of HLA-matched sibling living kidney donation while maintaining immune responsiveness to an mRNA vaccine (ClinicalTrials.gov: NCT00365846).

Clinical Spectrum of Gross Hematuria Following SARS-CoV-2 Vaccination With mRNA Vaccines

Background

Novel messenger RNA (mRNA)-based vaccines play an important role in current vaccination campaigns against SARS-CoV-2. They are highly efficacious and generally well tolerated. Vaccination in patients with immune-mediated kidney diseases is recommended. A number of cases with de novo or relapsing glomerulonephritis shortly after vaccine application have been reported, some of which presented with gross haematuria.

Methods

We collected 10 cases of macrohaematuria following mRNA-based severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccination at our tertiary care institution and referring centres. Additionally, we pooled all 25 published cases from the literature with ours to analyse their clinical characteristics.

Results

Most macrohaematuria episodes (72.2%) began within 2 days after vaccination, the majority after the second dose. In some individuals, repeated episodes occurred after subsequent doses of the same vaccine. A total of 65.7% of patients never had macrohaematuria before. A total of 45.7% were known to suffer from immunoglobulin A nephropathy (IgAN); the rest had no prior renal diagnosis. IgAN was the most frequent new diagnosis, but anti-neutrophil cytoplasmic antibody-associated vasculitis and anti-glomerular basement membrane disease were also identified. Acute kidney injury (AKI) occurred in 28.6% of patients, with an increase in serum creatinine not meeting Kidney Disease: Improving Global Outcomes AKI criteria in 28.6%. Treatment ranged from conservative management, renin–angiotensin–aldosterone system inhibitors, steroids and cyclophosphamide to plasmapheresis. While renal outcomes were mainly favourable in isolated IgAN, they were poor in patients with additional or isolated small vessel vasculitis.

Conclusion

Awareness of gross haematuria after SARS-CoV-2 vaccination is important. Close follow-up and additional work up, particularly in individuals without known underlying kidney disease or worsening renal function, is essential. For patients with vaccine-associated macrohaematuria, an alternative vaccine class might be considered for subsequent vaccinations.

Management of transthyretin amyloidosis

Transthyretin amyloidosis (ATTR amyloidosis) is a disease caused by deposition of transthyretin fibrils in organs and tissues, which causes their dysfunction. The clinical heterogeneity of ATTR amyloidosis and the variable presentation of symptoms at early disease stages, historically meant treatment delays. Diagnostic tools and therapy options of ATTR amyloidosis have markedly improved in recent years. The first Swiss Amyloidosis Network (SAN) meeting (Zurich, Switzerland, January 2020) aimed to define a consensus statement regarding the diagnostic work-up and treatment for systemic amyloidosis, tailored to the Swiss healthcare system. A consortium of 45 clinicians and researchers from all Swiss regions and universities was selected by the SAN committee to represent all sub-specialty groups involved in care of patients with amyloidosis. A steering committee conducted the literature search and analysis, wrote the critical synthesis and elaborated a list of statements that were evaluated by all the participants. These recommendations will improve outcomes and quality of life for patients with ATTR amyloidosis. A global review of these guidelines is planned every 3 years with a formal meeting of all the involved experts.

A multi-center retrospective cohort study defines the spectrum of kidney pathology in Coronavirus 2019 Disease (COVID-19)

Kidney failure is common in patients with Coronavirus Disease-19 (COVID-19) resulting in increased morbidity and mortality. In an international collaboration, 284 kidney biopsies were evaluated to improve understanding of kidney disease in COVID-19. Diagnoses were compared to five years of 63,575 native biopsies prior to the pandemic and 13,955 allograft biopsies to identify diseases increased in patients with COVID-19. Genotyping for APOL1 G1 and G2 alleles was performed in 107 African American and Hispanic patients. Immunohistochemistry for SARS-CoV-2 was utilized to assess direct viral infection in 273 cases along with clinical information at the time of biopsy. The leading indication for native biopsy was acute kidney injury (45.4%), followed by proteinuria with or without concurrent acute kidney injury (42.6%). There were more African American patients (44.6%) than patients of other ethnicities. The most common diagnosis in native biopsies was collapsing glomerulopathy (25.8%) which associated with high-risk APOL1 genotypes in 91.7% of cases. Compared to the five-year biopsy database, the frequency of myoglobin cast nephropathy and proliferative glomerulonephritis with monoclonal IgG deposits was also increased in patients with COVID-19 (3.3% and 1.7%, respectively), while there was a reduced frequency of chronic conditions (including diabetes mellitus, IgA nephropathy, and arterionephrosclerosis) as the primary diagnosis. In transplants, the leading indication was acute kidney injury (86.4%), for which rejection was the predominant diagnosis (61.4%). Direct SARS-CoV-2 viral infection was not identified. Thus, our multi-center large case series identified kidney diseases that disproportionately affect patients with COVID-19, demonstrated a high frequency of APOL1 high-risk genotypes within this group, with no evidence of direct viral infection within the kidney.

Acidosis and alkali therapy in patients with kidney transplant is associated with transcriptional changes and altered abundance of genes involved in cell metabolism and acid-base balance

BACKGROUND

Metabolic acidosis occurs frequently in patients with kidney transplant and is associated with higher risk for and accelerated loss of graft function. To date, it is not known whether alkali therapy in these patients improves kidney function and whether acidosis and its therapy is associated with altered expression of proteins involved in renal acid-base metabolism.

METHODS

We collected retrospectively kidney biopsies from 22 patients. Of these patients, 9 had no acidosis, 9 had metabolic acidosis (plasma HCO3- < 22 mmol/l), and 4 had acidosis and received alkali therapy. We performed transcriptome analysis and immunohistochemistry for proteins involved in renal acid-base handling.

RESULTS

We found the expression of 40 transcripts significantly changed between kidneys from non-acidotic and acidotic patients. These genes are mostly involved in proximal tubule amino acid and lipid metabolism and energy homeostasis. Three transcripts were fully recovered by alkali therapy: the Kir4.2 K+-channel, an important regulator of proximal tubule HCO3--metabolism and transport, ACADSB and SHMT1, genes involved in beta-oxidation and methionine metabolism. Immunohistochemistry showed reduced staining for the proximal tubule NBCe1 HCO3- transporter in kidneys from acidotic patients that recovered with alkali therapy. In addition, the HCO3-exchanger pendrin was affected by acidosis and alkali therapy.

CONCLUSIONS

Metabolic acidosis in kidney transplant recipients is associated with alterations in the renal transcriptome that are partly restored by alkali therapy. Acid-base transport proteins mostly from proximal tubule were also affected by acidosis and alkali therapy suggesting that the downregulation of critical players contributes to metabolic acidosis in these patients.

FC 001ACIDOSIS AND ALKALI THERAPY ARE ASSOCIATED WITH TRANSCRIPTIONAL CHANGES AND ALTERED ABUNDANCE OF GENES INVOLVED IN CELL METABOLISM AND BICARBONATE TRANSPORT IN KIDNEY TRANSPLANT RECIPIENTS

Background and Aims

Metabolic acidosis is a common event in kidney transplant recipients and has been associated to a higher risk of graft loss and mortality. In patients with CKD and acidosis, alkali therapy ameliorating acidosis appears to protect kidney function. However, it is still poorly understood how acidosis causes the detrimental effects to kidney graft function and how alkali therapy would interact with these mechanisms. Here we aim to identify transcriptomic alterations in kidney transplant recipients without metabolic acidosis in comparison to patients with metabolic acidosis with and without alkali therapy. Moreover, we examined immunolocalization of key proteins involved in acid-base base regulation in biopsies from these patients.

Method

We obtained 22 biopsies of patients 4-6 years after kidney transplantation. Among these patients, nine were not acidotic (serum [HCO3-] ≥ 22 mM), nine had acidosis ([HCO3-] &lt; 22 mM), and four had acidosis and received sodium bicarbonate (alkali therapy) fully correcting acidosis. Age, immunosuppressive drugs, time after transplantation, and eGFR were not statistically different between groups. RNA was extracted from biopsies and RNAseq was performed. Immunohistochemistry was performed for key proteins involved in the renal regulation of acid-base balance. Additionally, a control group of 6 non-transplanted healthy kidneys was included in the histology analysis.

Results

RNAseq analysis revealed 40 genes differentially expressed between acidosis and no acidosis groups. While most of the genes tended to be recovered by alkali therapy, only three fully recovered with bicarbonate supplementation (p-value &lt; 0.05 and log2(fold change) above 0.5). These genes were KCNJ15 (Kir4.2), SHMT1, and ACADSB. Renal localization of the genes was determined using single-cell RNA sequencing data (Ransick et al., Developmental Cell, 2019, doi.org/10.1016/j.devcel.2019.10.005). Most of the genes were expressed in the proximal tubule and were organized in the model shown in Figure 1A. Several of these genes participate in cell metabolism, such as beta-oxidation, and iron, folate, and methionine metabolism. Moreover, the K+-channel Kir4.2 regulates the activity of the electrogenic sodium bicarbonate cotransporter 1 (NBCe1, SLC4A4) and ammoniagenesis in renal proximal tubules. Immunofluorescence analysis showed that NBCe1 expression in proximal tubules was strongly reduced in patients who developed acidosis and was partially recovered in patients who received alkali therapy (Figure 1B). In type B intercalated cells, a similar pattern was observed for Pendrin (SLC26A4). No alteration in the expression of GDH (GLUD1), AE1 (SLC4A1), AQP2, CA2, RhCG (SLC42A3), and B1 subunit of the H+ATPase (ATP6V1B1) was observed in kidneys of treated or untreated patients with acidosis.

Conclusion

Kidney transplant recipients suffering from metabolic acidosis show distinct expression pattern of genes involved in cell metabolism and acid-base transport.

Collagen IVα345 dysfunction in glomerular basement membrane diseases. I. Discovery of a COL4A3 variant in familial Goodpasture's and Alport diseases

Diseases of the glomerular basement membrane (GBM), such as Goodpasture’s disease (GP) and Alport syndrome (AS), are a major cause of chronic kidney failure and an unmet medical need. Collagen IV^α345 is an important architectural element of the GBM that was discovered in previous research on GP and AS. How this collagen enables GBM to function as a permselective filter and how structural defects cause renal failure remain an enigma. We found a distinctive genetic variant of collagen IV^α345 in both a familial GP case and four AS kindreds that provided insights into these mechanisms. The variant is an 8-residue appendage at the C-terminus of the α3 subunit of the α345 hexamer. A knock-in mouse harboring the variant displayed GBM abnormalities and proteinuria. This pathology phenocopied AS, which pinpointed the α345 hexamer as a focal point in GBM function and dysfunction. Crystallography and assembly studies revealed underlying hexamer mechanisms, as described in Boudko et al. and Pedchenko et al. Bioactive sites on the hexamer surface were identified where pathogenic pathways of GP and AS converge and, potentially, that of diabetic nephropathy (DN). We conclude that the hexamer functions include signaling and organizing macromolecular complexes, which enable GBM assembly and function. Therapeutic modulation or replacement of α345 hexamer could therefore be a potential treatment for GBM diseases, and this knock-in mouse model is suitable for developing gene therapies.

Granulomatous interstitial nephritis in a patient with SARS-CoV-2 infection

Background

Acute kidney injury (AKI) associated with severe coronavirus disease 19 (COVID-19) is common and is a significant predictor of morbidity and mortality, especially when dialysis is required. Case reports and autopsy series have revealed that most patients with COVID-19 – associated acute kidney injury have evidence of acute tubular injury and necrosis - not unexpected in critically ill patients. Others have been found to have collapsing glomerulopathy, thrombotic microangiopathy and diverse underlying kidney diseases. A primary kidney pathology related to COVID-19 has not yet emerged. Thus far direct infection of the kidney, or its impact on clinical disease remains controversial. The management of AKI is currently supportive.

Case Presentation

The patient presented here was positive for SARS-CoV-2, had severe acute respiratory distress syndrome and multi-organ failure. Within days of admission to the intensive care unit he developed oliguric acute kidney failure requiring dialysis. Acute kidney injury developed in the setting of hemodynamic instability, sepsis and a maculopapular rash. Over the ensuing days the patient also developed transfusion-requiring severe hemolysis which was Coombs negative. Schistocytes were present on the peripheral smear. Given the broad differential diagnoses for acute kidney injury, a kidney biopsy was performed and revealed granulomatous tubulo-interstitial nephritis with some acute tubular injury. Based on the biopsy findings, a decision was taken to adjust medications and initiate corticosteroids for presumed medication-induced interstitial nephritis, hemolysis and maculo-papular rash. The kidney function and hemolysis improved over the subsequent days and the patient was discharged to a rehabilitation facility, no-longer required dialysis.

Conclusions

Acute kidney injury in patients with severe COVID-19 may have multiple causes. We present the first case of granulomatous interstitial nephritis in a patient with COVID-19. Drug-reactions may be more frequent than currently recognized in COVID-19 and are potentially reversible. The kidney biopsy findings in this case led to a change in therapy, which was associated with subsequent patient improvement. Kidney biopsy may therefore have significant value in pulling together a clinical diagnosis, and may impact outcome if a treatable cause is identified.

Expert recommendation from the Swiss Amyloidosis Network (SAN) for systemic AL-amyloidosis

Systemic amyloidosis is a heterogeneous group of diseases associated with protein misfolding into insoluble beta-sheet rich structures that deposit extracellularly in different organs, eventually compromising their function. There are more than 30 different proteins, known to be amyloidogenic with &ldquo;light chain&rdquo; (AL)-amyloidosis being the most common type, followed by transthyretin (ATTR)-, and amyloid protein A (AA)-amyloidosis. Systemic amyloidosis is a rare disease with an incidence of around 10 patients in 1 million inhabitants. Recently several new therapeutic options have been developed for subgroups of amyloidosis patients, and the introduction of novel therapies for plasma cell myeloma has led to an increase in the therapeutic armamentarium for plasma cell disorders, including AL amyloidosis. Among them, proteasome inhibitors, immunomodulatory agents (-imids), and monoclonal antibodies have been successfully introduced into clinical practice. Still, high-quality data from randomised controlled trials regarding the benefit of these cost-intensive drugs in AL amyloidosis are widely lacking, and due to the rarity of the disease many physicians will not gain routine experience in the management of these frail patients. The diagnosis of AL amyloidosis relies on a close collaboration between clinicians, pathologists, imaging experts, and sometimes geneticists. Diagnosis and treatment options in this complex disorder should be discussed in dedicated multidisciplinary boards. In January 2020, the first meeting of the Swiss Amyloidosis Network took place in Zurich, Switzerland. One aim of this meeting was to establish a consensus guideline regarding the diagnostic work-up and the treatment recommendations for systemic amyloidosis tailored to the Swiss health care system. Forty-five participants from different fields in medicine discussed many aspects of amyloidosis. These are the Swiss Amyloidosis Network recommendations which focus on diagnostic work-up and treatment of AL-amyloidosis.

P0004REDUCED EXPRESSION OF PROXIMAL ACID-BASE TRANSPORT PROTEINS IN KIDNEY TRANSPLANT PATIENTS WITH METABOLIC ACIDOSIS

Background and Aims

Metabolic acidosis (MA) is a frequent complication of chronic kidney disease and an independent risk factor for kidney disease progression and mortality. MA is highly prevalent after kidney transplantation (12%-58%)(1). However, there are scarcely any data available on the underlying pathomechanisms and in particular molecular mechanisms involved in metabolic acidosis after kidney transplantation. Thus, we wanted to investigate the expression of key acid base transport proteins in kidney biopsies of kidney transplant recipients with and without metabolic acidosis.

Method

We evaluated 22 kidney transplant biopsies including 9 biopsies from kidney transplant recipients (KTR) with MA, nine biopsies from KTRs without MA (control) and four biopsies from KTRs with MA that were consequently subjected to alkali therapy (Alkali therapy). Immunofluorescence staining was used to identify key renal acid-base transport proteins. Additionally, six control kidneys were analyzed. Immunofluorescence staining was used to identify key renal acid-base transport proteins along the nephron. In addition, RNA extraction and full RNA sequencing analysis of all biopsies –where available- was performed.

Results

In the proximal tubule, we observed reduced immunostaining for the sodium bicarbonate cotransporter NBCe1 (SLC4A4) in the MA group compared to the control and alkali group, whereas the alkali group demonstrated the strongest staining of all three groups. In the distal nephron, expression of the chloride/bicarbonate exchanger Pendrin (SLC26A4) and the B1 subunit of the V-ATPase (ATP6V1B1) were markedly stronger in the alkali and control group compared to the MA group.

Expression of other acid base proteins such as Renal ammonia transporter RhCG (SLC42A3), Carbonic Anhydrase II, Glutamate dehydrogenase, anion exchanger AE1 (SLC4A1) and the B2 subunit of the V-ATPase (ATP6V1B2) showed no difference among all groups. Interestingly, the B2 subunit was absent in the proximal tubule in transplant biopsies of all groups.

In kidney biopsies of transplant recipients with metabolic acidosis RNA abundance of NBCe1, CAII and Pendrin was lower while RhCG and B1 RNA counts were not different when compared to recipients without metabolic acidosis.

Conclusion

Our data demonstrate altered protein and mRNA expression of several key acid base transporters in kidney biopsies of transplant recipients with metabolic acidosis. Treatment with alkali may have the potential to reverse or prevent these changes in renal allografts after transplantation.

Blood CD9+ B cell, a biomarker of bronchiolitis obliterans syndrome after lung transplantation

Bronchiolitis obliterans syndrome is the main limitation for long-term survival after lung transplantation. Some specific B cell populations are associated with long-term graft acceptance. We aimed to monitor the B cell profile during early development of bronchiolitis obliterans syndrome after lung transplantation. The B cell longitudinal profile was analyzed in peripheral blood mononuclear cells from patients with bronchiolitis obliterans syndrome and patients who remained stable over 3 years of follow-up. CD24^hi CD38^hi transitional B cells were increased in stable patients only, and reached a peak 24 months after transplantation, whereas they remained unchanged in patients who developed a bronchiolitis obliterans syndrome. These CD24^hi CD38^hi transitional B cells specifically secrete IL-10 and express CD9. Thus, patients with a total CD9⁺ B cell frequency below 6.6% displayed significantly higher incidence of bronchiolitis obliterans syndrome (AUC = 0.836, PPV = 0.75, NPV = 1). These data are the first to associate IL-10-secreting CD24^hi CD38^hi transitional B cells expressing CD9 with better allograft outcome in lung transplant recipients. CD9-expressing B cells appear as a contributor to a favorable environment essential for the maintenance of long-term stable graft function and as a new predictive biomarker of bronchiolitis obliterans syndrome-free survival.

[The pathology of adverse events with immune checkpoint inhibitors]

BACKGROUND

Immunotherapy has gained importance with the development of new effective cancer treatments. Immune checkpoint inhibitors (ICI) are monoclonal antibodies that promote T‑cell mediated tumor immune rejection. Checkpoint blockade also carries the risk of inducing autoimmune reactions ("immune related adverse events", irAEs). The diagnosis and classification of irAEs constitute a new and important field in pathology.

AIM

Practice-oriented review of the diagnosis and classification of irAEs.

MATERIALS AND METHODS

Structured, selective literature review based on PubMed und UpToDate ® online.

RESULTS

The most common irAEs affect the skin, the gastrointestinal tract, the liver, and the respiratory system. The correct diagnosis and classification of irAEs by an interdisciplinary care team is essential for appropriate therapy and the prevention of long-term sequelae. Other important irAEs affect the endocrine organs, the heart, the joints, the kidneys and the nervous system. Because of their rarity and/or limited options for bioptic diagnosis, only limited data on the morphology and pathophysiology of these irAEs are currently available. Autopsies carried out after ICI therapy constitute an important element of quality control and allow better documentation of the incidence and pathogenesis of irAEs.

DISCUSSION

Pathology plays a central role in the diagnosis and treatment of irAEs. Future studies may contribute to a better mechanistic understanding of irAEs for individualized knowledge-based risk assessment.

Ureaplasma and Mycoplasma in kidney allograft recipients-A case series and review of the literature

Ureaplasma urealyticum and Mycoplasma hominis are common inhabitants of the human genital tract. Increasingly, serious and sometimes fatal infections in immunocompromised hosts have been reported, highlighting their pathogenic potential. We reviewed the clinical impact of positive Ureaplasma spp. and Mycoplasma spp. urine cultures in 10 renal allograft recipients who presented with sterile leukocyturia. Five recipients remained asymptomatic. Five patients were symptomatic with dysuria or pain at the graft site. Three patients developed biopsy-proven acute graft pyelonephritis with graft dysfunction. One of these patients additionally showed a renal abscess as demonstrated by magnetic resonance imaging (MRI). All were successfully treated. A literature search revealed a substantial number of case reports with severe and sometimes fatal Ureaplasma spp. or Mycoplasma spp. infections in immunocompromised patients. Colonization rate is high in renal transplant patients. A subset of patients is at risk for invasive disease.

Membranoproliferative glomerulonephritis and C3 glomerulopathy in children: change in treatment modality? A report of a case series

Background

Membranoproliferative glomerulonephritis (MPGN) with immune complexes and C3 glomerulopathy (C3G) in children are rare and have a variable outcome, with some patients progressing to end-stage renal disease (ESRD). Mutations in genes encoding regulatory proteins of the alternative complement pathway and of complement C3 (C3) have been identified as concausative factors.

Methods

Three children with MPGN type I, four with C3G, i.e. three with C3 glomerulonephritis (C3GN) and one with dense deposit disease (DDD), were followed. Clinical, autoimmune data, histological characteristics, estimated glomerular filtration rate (eGFR), proteinuria, serum C3, genetic and biochemical analysis were assessed.

Results

The median age at onset was 7.3 years and the median eGFR was 72 mL/min/1.73 m². Six children had marked proteinuria. All were treated with renin-angiotensin-aldosterone system (RAAS) blockers. Three were given one or more immunosuppressive drugs and two eculizumab. At the last median follow-up of 9 years after diagnosis, three children had normal eGFR and no or mild proteinuria on RAAS blockers only. Among four patients without remission of proteinuria, genetic analysis revealed mutations in complement regulator proteins of the alternative pathway. None of the three patients with immunosuppressive treatment achieved partial or complete remission of proteinuria and two progressed to ESRD and renal transplantation. Two patients treated with eculizumab revealed relevant decreases in proteinuria.

Conclusions

In children with MPGN type I and C3G, the outcomes of renal function and response to treatment modality show great variability independent from histological diagnosis at disease onset. In case of severe clinical presentation at disease onset, early genetic and biochemical analysis of the alternative pathway dysregulation is recommended. Treatment with eculizumab appears to be an option to slow disease progression in single cases.

FAT1 mutations cause a glomerulotubular nephropathy

Steroid-resistant nephrotic syndrome (SRNS) causes 15% of chronic kidney disease (CKD). Here we show that recessive mutations in FAT1 cause a distinct renal disease entity in four families with a combination of SRNS, tubular ectasia, haematuria and facultative neurological involvement. Loss of FAT1 results in decreased cell adhesion and migration in fibroblasts and podocytes and the decreased migration is partially reversed by a RAC1/CDC42 activator. Podocyte-specific deletion of Fat1 in mice induces abnormal glomerular filtration barrier development, leading to podocyte foot process effacement. Knockdown of Fat1 in renal tubular cells reduces migration, decreases active RAC1 and CDC42, and induces defects in lumen formation. Knockdown of fat1 in zebrafish causes pronephric cysts, which is partially rescued by RAC1/CDC42 activators, confirming a role of the two small GTPases in the pathogenesis. These findings provide new insights into the pathogenesis of SRNS and tubulopathy, linking FAT1 and RAC1/CDC42 to podocyte and tubular cell function.

The Role of T Cell Costimulation via DNAM-1 in Kidney Transplantation

DNAX accessory protein-1 (DNAM-1, CD226) is a co-stimulatory and adhesion molecule expressed mainly by natural killer cells and T cells. DNAM-1 and its two ligands CD112 and CD155 are important in graft-versus-host disease, but their role in solid organ transplantation is largely unknown. We investigated the relevance of this pathway in a mouse kidney transplantation model. CD112 and CD155 are constitutively expressed on renal tubular cells and strongly upregulated in acutely rejected renal allografts. In vitro DNAM-1 blockade during allogeneic priming reduced the allospecific T cell response but not the allospecific cytotoxicity against renal tubular epithelial cells. Accordingly, absence of DNAM-1 in recipient mice or absence of CD112 or CD155 in the kidney allograft did not significantly influence renal function and severity of rejection after transplantation, but led to a higher incidence of infarcts in CD112 and CD155 deficient kidney allografts. Thus, DNAM-1 blockade is not effective in preventing transplant rejection. Despite of being highly expressed, CD112 and CD155 do not appear to play a major immunogenic role in kidney transplantation. Considering the high incidence of renal infarcts in CD112 and CD155 deficient grafts, blocking these molecules might be detrimental.

Hepatitis From Spiroplasma sp. in an Immunocompromised Patient

A 70-year-old lung transplant recipient patient was admitted with fever, nausea, abdominal pain, peripheral edema and pronounced weakness. An initial work-up for presumed infection revealed cholestatic hepatitis, leukocytosis and thrombocytopenia, but failed to detect a pathogen. An increased glucose uptake exclusively in the liver was demonstrated by positron emission tomography. Liver biopsy showed basophilic inclusions in the cytoplasm of hepatocytes. Broad- range 16S rRNA gene PCR followed by sequence analysis yielded Spiroplasma sp. in two independent blood samples and the liver biopsy, confirming Spiroplasma sp. as the causative agent. Antibiotic treatment with doxycycline and azithromycin led to complete recovery.

[CME. Fabry disease: rare but not to be missed]

Beim Morbus Fabry handelt es sich um eine X-chromosomal-rezessiv vererbbare lysosomale Speicherkrankheit, die durch einen Enzymdefekt der α-Galaktosidase A entsteht. Es kommt zu einer Anreicherung der Sphingolipide in den Lysosomen des Gefässendothels sowie verschiedener Organe. Am häufigsten involviert sind Niere, Herz, Nervensystem, Gastrointestinum sowie die Augen. Nicht selten wird ein schwerer progredienter Krankheitsverlauf beobachtet, mit ersten Symptomen bereits in der Kindheit. Aufgrund der unspezifischen Krankheitssymptome ist es nicht einfach, die Erkrankung zu diagnostizieren, sodass sie häufig erst im Erwachsenenalter erkannt wird. Die ersten Symptome in der Kindheit beginnen oft mit schmerzhaften Akroparästhesien im Rahmen von peripheren Neuropathien. Hinzu kommen Müdigkeit, Fieberschmerzkrisen, gastrointestinale Symptome. Im fortgeschrittenen Stadium kann Morbus Fabry aufgrund von Endorganschäden wie Niereninsuffizienz, Schlaganfall oder Herzrhythmussstörungen bei Kardiomyopathie tödlich enden. Meistens sind Männer schwerer von der Krankheit betroffen. Die Prävalenz in der Gesamtbevölkerung wird mit 1:40 000 bis 1:70 000 geschätzt. Die einzige kausale Therapie stellt aktuell der Enzymersatz dar.

Native kidney biopsies in Armenian and Swiss children: high prevalence of amyloidosis in Yerevan and of IgA nephropathy in Zurich

The spectrum of pathology in native kidney biopsies varies considerably between different countries. Based on similar biopsy policy and joint workup, biopsy data of native kidneys of children in Yerevan (Armenia) and Zurich (Switzerland) were compared over a period of two decades (1993-2002 and 2003-2012). A total of 487 renal biopsies in Yerevan (EVN), n = 253; median age 11.2 years (range 0.8-18; 56 % males) and in Zurich (ZRH), n = 234; median age 8.7 years (range 0.1-18; 61 % males) were analyzed. Biopsies from EVN were locally analyzed by light microscopy (LM) and sent to ZRH for electron microscopy (EM) and immunohistochemistry. Biopsies from ZRH were evaluated by LM, EM, and immunofluorescence. The significant difference concerns the high frequency of amyloidosis in EVN (25.4 % in the first and 19.4 % in the second decade vs. 0 % in ZRH) and of IgA nephropathy in ZRH (30.2 % in the first and 26.1 % in the second decade vs. 8.1 in EVN). Certain forms of glomerulonephritis (membranoproliferative type I and membranous) and primary focal segmental glomerulosclerosis tended to be more frequent in EVN than in ZRH. Amyloid nephropathy due to familial Mediterranean fever is still highly frequent in Armenia with a slight decrease in the second decade. In Switzerland, the most common finding was IgA nephropathy.

[Calcified]

A 73-year-old woman was referred due to an acute and progressive worsening of a previously mildly impaired kidney function of unknown origin. The kidney biopsy showed a phosphate nephropathy. We identified Colophos®, a phosphate-containing purgative as the causing agent, which the patient had received for bowel cleansing for a colonoscopy one day before the detection of the acute kidney failure. During the following months the kidney function initially declined further and then improved. Most cases of phosphate nephropathy are associated with the ingestion of phosphate-containing purgatives. Persons at risk are women, elderly persons, patients with impaired kidney function, hypertension, and dehydration. The consequence is sometimes an irreversible tubulointerstitial injury that can lead to end-stage renal disease in a minority of the cases.

Antibody-mediated kidney allograft rejection: therapeutic options and their experimental rationale

With the advent of novel therapies to directly intervene with B cell immunity and complement activation, antibody-mediated kidney allograft rejection (AMR) has come into the focus of transplant immunologists. Intravenous immunoglobulin, rituximab, bortezomib, and eculizumab have been used to treat patients with acute AMR, apart from the standard treatment of antibody removal with plasma exchange or immunoadsorption and steroid pulses. This article describes the experimental rationale and summarizes the still limited clinical experience with these novel therapies in the transplant setting. Results with the standard treatment for acute AMR, including intense plasmapheresis, intravenous immunoglobulins, and steroids are good with a graft survival of 80% at 18 months. In contrast, patients suffering from chronic AMR have significant irreversible damage in their grafts with substantially impaired graft survival. Thus, the authors propose a step-wise escalation of therapy in refractory cases of acute AMR and advocate an urgent need for controlled therapeutic trials for acute and chronic AMR not to inflict unnecessary harm on our patients by uncontrolled polypragmasy.

Age-related penetrance of hereditary atypical hemolytic uremic syndrome

Hereditary atypical hemolytic uremic syndrome (aHUS), a dramatic disease frequently leading to dialysis, is associated with germline mutations of the CFH, CD46, or CFI genes. After identification of the mutation in an affected aHUS patient, single-site gene testing of relatives is the preventive care perspective. However, clinical data for family counselling are scarce. From the German-Speaking-Countries-aHUS-Registry, 33 index patients with mutations were approached for permission to offer relatives screening for their family-specific mutations and to obtain demographic and clinical data. Mutation screening was performed using direct sequencing. Age-adjusted penetrance of aHUS was calculated for each gene in index cases and in mutation-positive relatives. Sixty-one relatives comprising 41 parents and 20 other relatives were enrolled and mutations detected in 31/61. In total, 40 research participants had germline mutations in CFH, 19 in CD46 and in 6 CFI. Penetrance at age 40 was markedly reduced in mutation-positive relatives compared to index patients overall with 10% versus 67% (P < 0.001); 6% vs. 67% (P < 0.001) in CFH mutation carriers and 21% vs. 70% (P= 0.003) in CD46 mutation carriers. Age-adjusted penetrance for hereditary aHUS is important to understand the disease, and if replicated in the future, for genetic counselling.

Periostin is induced in glomerular injury and expressed de novo in interstitial renal fibrosis

Matricellular proteins participate in the pathogenesis of chronic kidney diseases. We analyzed glomerular gene expression profiles from patients with proteinuric diseases to identify matricellular proteins contributing to the progression of human nephropathies. Several genes encoding matricellular proteins, such as SPARC, THBS1, and CTGF, were induced in progressive nephropathies, but not in nonprogressive minimal-change disease. Periostin showed the highest induction, and its transcript levels correlated negatively with glomerular filtration rate in both glomerular and tubulointerstitial specimen. In well-preserved renal tissue, periostin localized to the glomerular tuft, the vascular pole, and along Bowman's capsule; no signal was detected in the tubulointerstitial compartment. Biopsies from patients with glomerulopathies and renal dysfunction showed enhanced periostin expression in the mesangium, tubular interstitium, and sites of fibrosis. Periostin staining correlated negatively with renal function. α-smooth muscle actin-positive mesangial and interstitial cells localized close to periostin-positive sites, as indicated by co-immunofluorescence. In vitro stimulation of mesangial cells by external addition of TGF-β1 resulted in robust induction of periostin. Addition of periostin to mesangial cells induced cell proliferation and decreased the number of cells expressing activated caspase-3, a marker of apoptosis. These human data indicate for the first time a role of periostin in glomerular and interstitial injury in acquired nephropathies.

Anti-hLAMP2-antibodies and dual positivity for anti-GBM and MPO-ANCA in a patient with relapsing pulmonary-renal syndrome

BACKGROUND

Pulmonary-renal syndrome associated with anti-glomerular basement membrane (GBM) antibodies, also known as Goodpasture's syndrome, is a rare but acute and life-threatening condition. One third of patients presenting as anti-GBM antibody positive pulmonary-renal syndrome or rapidly progressive glomerulonephritis are also tested positive for anti-neutrophil cytoplasmic antibodies (ANCA). Whilst anti-GBM disease is considered a non-relapsing condition, the long-term course of double-positive patients is less predictable.

CASE PRESENTATION

We report a patient with such dual positivity, who presented with pulmonary hemorrhage, crescentic glomerulonephritis and membranous nephropathy. Plasmapheresis in combination with immunosuppressive therapy led to a rapid remission but the disease relapsed after two years. The serum of the patient was tested positive for antibodies to human lysosomal membrane protein 2 (hLAMP2), a novel autoantigen in patients with active small-vessel vasculitis (SVV). The anti-hLAMP2 antibody levels correlated positively with clinical disease activity in this patient.

CONCLUSION

We hypothesize that this antibody may indicate a clinical course similar to ANCA-associated vasculitis in double-positive patients. However, this needs to be confirmed on comprehensive patient cohorts.

[Rheumatoid arthritis and interstitial lung alterations - a clear case, isn't it?]

In a patient with rheumatoid arthritis (RA) and asymptomatic, diffuse reticulo-nodular lung parenchymal alterations with upper lobe predominance, a Caplan syndrome (CS) was diagnosed. According to the size of the pulmonary nodules, classification into two subtypes of the CS has been proposed: the classic (Caplan) type and the silicotic type. Patients with CS often present with considerable x-ray or computertomographic changes but relatively few symptoms. However, in case of respiratory symptoms, infectious complications or pneumotoxic side effects of the immunsuppressive/immune-modulating pharmacotherapy for RA must be encountered in the differential diagnosis.

Recurrence of membranoproliferative glomerulonephritis after renal transplantation in Denys-Drash

Denys-Drash syndrome (DDS) consists of the triad of nephropathy, male pseudohermaphroditism, and Wilms tumor caused by mutations within exons 8 or 9 of the Wilms tumor suppressor gene 1. Early onset nephrotic syndrome progresses to end-stage renal failure. The characteristic histological lesion is diffuse mesangial sclerosis. Here, we report on a boy with DDS who presented early with diffuse mesangial sclerosis, but subsequently also developed immune complex glomerulonephritis with a membranoproliferative pattern (MPGN-pattern GN) in his native kidneys. Four years after renal transplantation, immune complex glomerulonephritis with an MPGN pattern recurred in the renal graft resulting in proteinuria and progressive renal insufficiency.

Podoplanin-positive cells are a hallmark of encapsulating peritoneal sclerosis

BACKGROUND

Encapsulating peritoneal sclerosis (EPS) and simple peritoneal sclerosis are important complications of long-term peritoneal dialysis (PD). Podoplanin is expressed by mesothelial cells and lymphatic vessels, which are involved in inflammatory reactions in the peritoneal cavity.

METHODS

We studied 69 peritoneal biopsies from patients on PD (n = 16), patients with EPS (n = 18) and control biopsies taken at the time of hernia repair (n = 15) or appendectomy (n = 20). Immunohistochemistry was performed to localize podoplanin. Additionally, markers of endothelial cells, mesothelial cells, myofibroblasts (smooth muscle actin), proliferating cells, and double labelling for smooth muscle actin/podoplanin were used on selected biopsies.

RESULTS

Podoplanin was present on the endothelium of lymphatic vessels in the submesothelial fibrous tissue and on mesothelial cells. In patients on PD and in biopsies with appendicitis, the mesothelial cells demonstrated a cuboidal appearance and circumferential podoplanin staining, with gaps between the cells. The number of lymphatic vessels was variable, but prominent at sites of fibrosis. In patients with EPS, a diffuse infiltration of podoplanin-positive cells with a fibroblastic appearance was present in 15 out of 18 biopsies. This pattern was focally present in 3 out of 16 on PD and none in the 35 controls. The podoplanin-positive cells did not express the endothelial marker or the mesothelial marker (calretinin).

CONCLUSIONS

EPS is characterized by a population of podoplanin and smooth muscle actin double-positive cells. Podoplanin might be a suitable morphological marker supporting the diagnosis and might be involved in the pathogenesis of EPS.

[Anti-RNA polymerase III antibodies in scleroderma renal crisis]

HISTORY AND CLINICAL FINDINGS

A 67-year old patient underwent a kidney biopsy because of newly diagnosed hypertension, haemolytic anemia with fragmentocytes and acute kidney failure requiring dialysis therapy. The biopsy showed thrombotic microangiopathy. Since last winter Raynaud's phenomenon and changes of hands and lips were recognised.

INVESTIGATIONS

Initial immunological tests revealed anti-nuclear antibodies (ANA) but neither anti-centromere nor anti-Scl70 antibodies. The positive analysis of anti-RNA polymerase III antibodies confirmed the clinical suspicion of scleroderma renal crisis in the setting of first diagnosis of systemic sclerosis.

TREATMENT AND COURSE

After diagnosis therapy with lisinopril, candesartan and amlodipin was established. Four months after discharge dialysis dependency persisted.

CONCLUSION

Scleroderma renal crisis is an important differential diagnosis in the setting of acute kidney failure. Medical history, clinical examination and immunological test confirm the diagnosis. The mainstay of therapy is aggressive blood pressure control with ACE-inhibitors (or angiotensin receptor blocking agents).

Kidney transplantation in mice using left and right kidney grafts

BACKGROUND

Mouse kidney transplantation is a powerful tool for scientific research. The conventional method uses only the left donor kidney for grafting because of shorter renal vessels on the right side.

MATERIALS AND METHODS

We developed a new technique of harvesting both left and right kidneys from one donor mouse, and separately transplanted them into two recipients. Forty-six kidney grafts (23 left, 23 right kidneys) were transplanted to 46 recipient mice. Life-supporting kidney transplantation (in which both recipient kidneys were removed) was performed in 12 recipients (six of each group).

RESULTS

Cold ischemia times were considerably longer for the second kidney graft (2.5-3 versus 1 h), which resulted in reduced graft function at early time points. However, the 14 d survival rate was comparable with 80% for right and 70% for left kidney grafts. Recipient animals were sacrificed between 1 and 6 wk after transplantation. Histologic examination of surviving grafts showed intact renal parenchyma, whereas total necrosis was usually seen in failed grafts. The causes of graft failure were thrombosis of the renal artery, narrow outflow of the renal vein, and fistula of the ureter. In a subgroup of animals, specific staining for apoptosis was performed. A tendency for a higher rate of apoptosis was seen at 1 wk compared with 6 wk post-transplant, but no correlation with cold ischemia time was found.

CONCLUSION

We report a new microsurgical technique of mouse kidney transplantation using both right and left donor kidneys as grafts for two recipient mice. Right kidney grafts showed equal survival compared with left kidney grafts. Thus, this technique reduces overall operating time and costs for microsurgery experiments.

Atheroembolic disease--a frequently missed diagnosis: results of a 12-year matched-pair autopsy study

Diagnosis of atheroembolic disease (AD) is challenging, because no specific test is available and AD often masquerades as other clinical conditions. We conducted the current study to investigate the relative frequency of autopsy-proven AD over time, to describe its clinical presentation, and to identify risk factors for AD. We screened 2066 autopsy reports from 1995 to 2006 for AD. For each AD case, a control patient without AD was matched for age, sex, and autopsy year. Diagnostic and therapeutic interventions (surgery, catheter interventions, and drug treatment) in the last 6 months before death, as well as clinical and laboratory parameters during the last hospitalization, were retrieved from electronic charts. We identified 51 patients with AD. Among these only 6 (12%) had been diagnosed clinically. The organs most often affected were kidney (71%), spleen (37%), and lower gastrointestinal tract (22%). The relative AD frequency decreased over time from 3.5 to 0.5 per 100 autopsies, whereas the frequency of clinically suspected and biopsy-proven AD remained constant. Among clinical signs, skin lesions such as livedo reticularis and blue toe (33% vs. 14%; p = 0.04) were significantly increased in AD patients compared with the matched controls. We also observed a trend for higher incidence of eosinophilia and proteinuria in AD patients. Vascular interventions within 6 months before death were highly associated with AD (55% vs. 29%; p = 0.01), and in a multivariable analysis this remained the only significant risk factor for AD. Thus, the diagnosis of AD is frequently missed. Vascular interventions represent the most important risk factor for AD and should be performed restrictively in high-risk patients.