The spectrum of glomerular and vascular kidney pathology associated with myeloproliferative neoplasms.

A high prevalence of chronic kidney disease (CKD) occurs in patients with myeloproliferative neoplasms (MPN). However, MPN-related glomerulopathy (MPN-RG) may not account for the entirety of CKD risk in this population. The systemic vasculopathy encountered in these patients raises the hypothesis that vascular nephrosclerosis may be a common pattern of injury in patients with MPN and with CKD. In an exhaustive, retrospective, multicenter study of MPN kidney biopsies in four different pathology departments, we now describe glomerular and vascular lesions and establish clinicopathologic correlations. Our study encompassed 47 patients with MPN who underwent a kidney biopsy that included 16 patients with chronic myeloid leukemia (CML) and 31 patients with non-CML MPN. Fourteen cases met a proposed definition of MPN-RG based on mesangial sclerosis and hypercellularity, as well as glomerular thrombotic microangiopathy. MPN-RG was significantly associated with both myelofibrosis and poorer kidney survival. Thirty-three patients had moderate-to-severe arteriosclerosis while 39 patients had moderate-to-severe arteriolar hyalinosis. Multivariable models that included 188 adult native kidney biopsies as controls revealed an association between MPN and chronic kidney vascular damage, which was independent of established risk factors such as age, diabetes mellitus and hypertension. Therefore, MPN-RG is associated with myelofibrosis and has a poor kidney prognosis. Thus, our findings suggest that the kidney vasculature is a target during MPN-associated vasculopathy and establish a new link between MPN and CKD. Hence, these results may raise new hypotheses regarding the pathophysiology of vascular nephrosclerosis in the general population.

Detection and localization of calcium oxalate in kidney using synchrotron deep ultraviolet fluorescence microscopy.

Renal oxalosis is a rare cause of renal failure whose diagnosis can be challenging. Synchrotron deep ultraviolet (UV) fluorescence was assayed to improve oxalosis detection on kidney biopsies spatial resolution and sensitivity compared with the Fourier transform infrared microspectroscopy gold standard. The fluorescence spectrum of synthetic mono-, di- and tri-hydrated calcium oxalate was investigated using a microspectrometer coupled to the synchrotron UV beamline DISCO, Synchrotron SOLEIL, France. The obtained spectra were used to detect oxalocalcic crystals in a case control study of 42 human kidney biopsies including 19 renal oxalosis due to primary (PHO, n = 11) and secondary hyperoxaluria (SHO, n = 8), seven samples from PHO patients who received combined kidney and liver transplants, and 16 controls. For all oxalocalcic hydrates samples, a fluorescence signal is detected at 420 nm. These spectra were used to identify standard oxalocalcic crystals in patients with PHO or SHO. They also revealed micrometric crystallites as well as non-aggregated oxalate accumulation in tubular cells. A nine-points histological score was established for the diagnosis of renal oxalosis with 100% specificity (76-100) and a 73% sensitivity (43-90). Oxalate tubular accumulation and higher histological score were correlated to lower estimated glomerular filtration rate and higher urinary oxalate over creatinine ratio.

Nanometric Chemical Speciation of Abnormal Deposits in Kidney Biopsy: Infrared-Nanospectroscopy Reveals Heterogeneities within Vancomycin Casts.

Infrared (IR) spectromicroscopy allows chemical mapping of a kidney biopsy. It is particularly interesting for chemical speciation of abnormal tubular deposits and calcification. In 2017, using IR spectromicroscopy, we described a new entity called vancomycin cast nephropathy. However, despite recent progresses, the IR microspectrometer spatial resolution is intrinsically limited by diffraction (a few micrometers). Combining atomic force microscopy and IR lasers (AFMIR) allows acquisition of infrared absorption spectra with a resolution and sensitivity in between 10 and 100 nm. Here we show that AFMIR can be used on standard paraffin embedded kidney biopsies. Vancomycin cast could be identified in a damaged tubule. Interestingly unlike standard IR spectromicroscopy, AFMIR revealed heterogeneity of the deposits and established that vancomycin coprecipitated with phosphate containing molecules. These findings highlight the high potential of this approach with nanometric spatial resolution which opens new perspectives for studies on drug-induced nephritis, nanocrystals, and local lipid or carbohydrates alterations.

Prevalence of tubulopathy and association with renal function loss in HIV-infected patients.

BACKGROUND: The incidence of chronic kidney disease (CKD) is 10 times higher in human immunodeficiency virus (HIV)-infected patients than in the general population. We explored the prevalence and determinants of proximal tubular dysfunction (PTD) in HIV-infected individuals, and assessed the impact of the tubulopathy on the estimated glomerular filtration rate (eGFR) outcome. METHODS: A cohort study was performed on 694 outpatients followed in a French centre to analyse the prevalence of PTD, the diagnosis performance of screening tools and the associated factors. eGFR was prospectively evaluated to analyse the predictive value of the tubulopathy on eGFR decrease. RESULTS: At inclusion, 14% of the patients presented with PTD and 5% with CKD. No individual tubular marker, including non-glomerular proteinuria, glycosuria dipstick or hypophosphataemia, registered sufficient performance to identify PTD. We found a significant interaction between tenofovir disoproxil fumarate exposure and ethnicity (P = 0.03) for tubulopathy risk. Tenofovir disoproxil fumarate exposure was associated with PTD in non-Africans [adjusted odds ratio (aOR) = 4.71, P < 10-3], but not in patients of sub-Saharan African origin (aOR = 1.17, P = 0.73). Among the 601 patients followed during a median of 4.3 years, 13% experienced an accelerated eGFR decline. Unlike microalbuminuria and glomerular proteinuria, tubulopathy was not associated with accelerated eGFR decline. CONCLUSION: PTD is not rare in HIV-infected individuals but is less frequent in sub-Saharan African patients and is associated with tenofovir disoproxil fumarate exposure only in non-Africans. Its diagnosis requires multiple biochemical testing and it is not associated with an accelerated eGFR decline.

Vancomycin-Associated Cast Nephropathy.

Vancomycin is a widely prescribed antibiotic, but the exact nature of vancomycin-associated nephrotoxicity is unclear, in particular when considering the frequent coadministration of aminoglycosides. We describe here the initial case of a 56-year-old woman with normal renal function developing unexplained ARF without hypovolemia after administration of vancomycin without coadministration of aminoglycosides. Studying the patient's renal biopsy specimen, we ascertained that obstructive tubular casts composed of noncrystal nanospheric vancomycin aggregates entangled with uromodulin explained the vancomycin-associated ARF. We developed in parallel a new immunohistologic staining technique to detect vancomycin in renal tissue and confirmed retrospectively that deleterious vancomycin-associated casts existed in eight additional patients with acute tubular necrosis in the absence of hypovolemia. Concomitant high vancomycin trough plasma levels had been observed in each patient. We also reproduced experimentally the toxic and obstructive nature of vancomycin-associated cast nephropathy in mice, which we detected using different in vivo imaging techniques. In conclusion, the interaction of uromodulin with nanospheric vancomycin aggregates represents a new mode of tubular cast formation, revealing the hitherto unsuspected mechanism of vancomycin-associated renal injury.

Flyscan opportunities in medicine: the case of quantum rattle based on gold quantum dots.

The new rapid scan method, Flyscan mode, implemented on the DiffAbs beamline at Synchrotron SOLEIL, allows fast micro-X-ray fluorescence data acquisition. It paves the way for applications in the biomedical field where a large amount of data is needed to generate meaningful information for the clinician. This study presents a complete set of data acquired after injection of gold-cluster-enriched mesoporous silica nanospheres, used as potential theranostic vectors, into rats. While classical X-ray fluorescence investigations (using step-by-step acquisitions) are based on a limited number of samples (approximately one per day at the DiffAbs beamline), the Flyscan mode has enabled gathering information on the interaction of nanometer-scale vectors in different organs such as liver, spleen and kidney at the micrometer scale, for five rats, in only a single five-day synchrotron shift. Moreover, numerous X-ray absorption near-edge structure spectra, which are beam-time-consuming taking into account the low concentration of these theranostic vectors, were collected.

Simulation-based learning in nephrology.

Simulation is a technique to replace and amplify real experiences with guided ones that evoke or replicate substantial aspects of the real world in a fully interactive fashion. In nephrology (a particularly complex specialty), simulation can be used by patients, nurses, residents, and attending physicians alike. It allows one to learn techniques outside the stressful environment of care such as central venous catheter placement, arteriovenous fistula management, learning about peritoneal dialysis, or performing a kidney biopsy. Serious games and virtual reality are emerging methods that show promise. Simulation could also be important in relational aspects of working in a team or with the patient. The development of simulation as a teaching tool in nephrology allows for maintaining high-quality training for residents, tailored to their future practice, and minimizing risks for patients. Additionally, this education helps nephrologists maintain mastery of technical procedures, making the specialty attractive to younger generations. Unfortunately, the inclusion of simulation training programmes faces occasional logistical or funding limitations that universities must overcome with the assistance and innovation of teaching nephrologists. The impact of simulation-based teaching on clinical outcomes needs to be investigated in clinical studies.

Corrigendum to Persistent Aseptic Pyelonephritis After Acute Bacterial Pyelonephritis: Possible Role of Corticosteroids Kidney International Reports, Volume 7, Issue 8, August 2022, Pages 1897-1900.

[This corrects the article DOI: 10.1016/j.ekir.2022.05.025.].

Exome-First Strategy in Adult Patients With CKD: A Cohort Study.

Introduction: Exome sequencing (ES) has widened the field of nephrogenomics in adult nephrology. In addition to reporting the diagnostic yield of ES in an adult cohort study, we investigated the clinical implications of molecular diagnosis and developed a clinical score to predict the probability of obtaining positive result. Methods: From September 2018 we have used ES to prospectively perform a first-tier liberal exploration of adult nephropathies of unknown origin and/or when a genetic kidney disease was clinically suggested. We also analyzed copy number variant using the same assay. Results: Molecular diagnosis was made in 127 of 538 patients sequenced (diagnostic yield: 24%), comprising 47 distinct monogenic disorders. Eight of these monogenic disorders (17% [8/47]) accounted for 52% of genetic diagnoses. In 98% (n = 125/127) of the patients, the genetic information was reported to have major clinical implications. We developed a 4-value clinical score to predict the probability of obtaining a molecular diagnosis (area under the receiver operating characteristics curve [AUC] 0.726 [95% confidence interval: 0.670-0.782]) (available at http://allogenomics.com/score). Conclusion: This study reinforces the role of ES as a first-tier exploration for adult chronic kidney disease patients in whom phenotypes are often poor and atypical. Although external validation is required, our clinical score could be a useful tool for the implementation of nephrogenomics in adults.

Apixaban Prophylactic Anticoagulation in Patients with Nephrotic Syndrome.

Background Nephrotic syndrome (NS) is associated with an increased risk of thromboembolic events (TEs), due to hemostatic derangements. The use of direct oral anticoagulants (DOACs) in the prevention of TE has not been studied intensively in patients suffering from NS. Methods The method included retrospective analysis of consecutive incident patients with NS due to glomerular disease, receiving apixaban for thromboprophylaxis. It is an uncontrolled, single-center study. Results We identified 27 patients treated with apixaban for the prevention of TEs, in the context of NS. During follow-up, apixaban minimal blood concentration (trough level; Cmin) and maximum blood concentration (Cmax) levels were measured. The mean duration of the anticoagulant treatment was 153 days (±132). Patients were followed for a mean of 14.7 months (±8.4) since the introduction of apixaban. Three patients had a TE at the time of NS diagnosis. Two patients had pulmonary embolism (PE) and one patient presented a stroke in a lupus membranous nephropathy context. One patient developed PE approximately 2 months after the introduction of apixaban treatment. No minor or major bleeding events were noticed. Conclusion The present study shows that patients, suffering from severe NS under anticoagulant therapy with apixaban had a reduced risk of venous and arterial TEs compared with patients previously described in the literature, without increased risk of bleeding.

Kidney disease in antiphospholipid antibody syndrome: Risk factors, pathophysiology and management.

Antiphospholipid antibody syndrome (APLS) is a rare autoimmune disease characterized by recurrent arterial and venous thromboembolic events, pregnancy related complications as well as the persistent detection of antiphospholipid antibodies at a 12 week interval. Renal complications tend to occur in 3% of APLS patients, with renal artery stenosis being the most common kidney related complication. Renal pathology may be subdivided into macro as well as microvascular thrombotic complications with stenosis, thrombosis and infarction representing the principle macrovascular events and APLS nephropathy representing the predominant microvascular complication. APLS related kidney disease may present with an array of heterogenous manifestations ranging from hematuria and non-nephrotic range proteinuria to hypertension or as part of a severe, life threatening and fulminant multiorgan failure disorder known as catastrophic antiphospholipid antibody syndrome (CAPS). Management of APLS related renal complications depends on the site of vascular injury, the thromboembolic risk profile based on the subtype, isotype and titer of the autoantibodies as well as the severity of the injury. Primary prophylaxis in these patients primarily revolves around the use of low dose aspirin, with prophylactic anticoagulation during events that increase thromboembolic like surgery and hospitalization. Anticoagulation is the cornerstone of treatment of APLS related kidney disease with INR targets varying depending on the associated venous or arterial thrombosis. Immunosuppression with the likes of rituximab, mTOR inhibitors, eculizumab and belimumab have been used with some success, but lack randomized control trial validation for their use. Pulsed corticosteroids with Plasmapheresis and intravenous immunoglobulins is the recommended treatment for CAPS.

beta-arrestin 2 oligomerization controls the Mdm2-dependent inhibition of p53.

beta-arrestins (beta-arrs), two ubiquitous proteins involved in serpentine heptahelical receptor regulation and signaling, form constitutive homo- and heterooligomers stabilized by inositol 1,2,3,4,5,6-hexakisphosphate (IP6). Monomeric beta-arrs are believed to interact with receptors after agonist activation, and therefore, beta-arr oligomers have been proposed to represent a resting biologically inactive state. In contrast to this, we report here that the interaction with and subsequent titration out of the nucleus of the protooncogene Mdm2 specifically require beta-arr2 oligomers together with the previously characterized nucleocytoplasmic shuttling of beta-arr2. Mutation of the IP6-binding sites impair oligomerization, reduce interaction with Mdm2, and inhibit p53-dependent antiproliferative effects of beta-arr2, whereas the competence for receptor regulation and signaling is maintained. These observations suggest that the intracellular concentration of beta-arr2 oligomers might control cell survival and proliferation.

Renal involvement in IgG4-related disease.

IgG4-RD may affect several organs including kidneys. The kidney is involved in approximately 20% of patient with IgG4-RD. The most common intrinsic kidney disease is tubulointerstitial nephritis (IgG4-TIN). Retroperitoneal fibrosis (IgG4-RPF) may induce obstructive acute renal failure. More rarely, IgG4-RKD can manifest as a glomerular disease, in particular as a membranous nephropathy (MN). It mostly affects middle-aged to elderly men and causes acute or chronic renal dysfunction, multiple hypodense lesions on CT-Scan and various extra-renal lesions. Increased serum IgG4 and hypocomplementemia are the most important serological findings for the diagnosis of IgG4-RD and thus should be systematically assessed when IgG4-RKD is suspected. Specific diagnosis criteria for IgG4-TIN including interstitial infiltration of IgG4-positive plasma cells, storiform fibrosis and tubular basement membrane immune complex deposits have been proposed. Corticosteroids are effective and remain the first-line therapy but relapses or severe forms could respond to immunosuppressive therapy.

Rituximab in Patients With Phospholipase A2 Receptor-Associated Membranous Nephropathy and Severe CKD.

INTRODUCTION: Patients with phospholipase A2 receptor (PLA2R)-associated membranous nephropathy and stage 4 or 5 chronic kidney disease are at high risk of end-stage kidney disease. In recent years, rituximab (RTX) emerged as a safe and efficient treatment for patients with PLA2R-associated membranous nephropathy. Whether its use is also appropriate in patients with an estimated glomerular filtration rate <30 ml/min per 1.73 m2 has not been investigated. METHODS: We retrospectively reviewed characteristics and outcome of 13 patients with PLA2R-associated membranous nephropathy and stage 4 or 5 chronic kidney disease who received a total of 14 consecutive RTX treatments from January 2012 to March 2018. The treatment regimen consisted of either 2 weekly infusions of 375 mg/m2 or 2 RTX infusions of 1 g/d two weeks apart. When needed, the regimen was repeated to achieve immunological remission. RESULTS: The mean estimated glomerular filtration rate, serum albumin level, and urinary protein level at the first RTX infusion were 18 ± 7 ml/min per 1.73 m2, 25.2 ± 5.4 g/l, and 13.2 ± 7.5 g/d, respectively, with all patients being tested positive for serum PLA2R antibodies. Ten treatment courses led to an increase in estimated glomerular filtration rate and remission of nephrotic syndrome after a median follow-up of 40.8 months (interquartile range, 14.8-46.8). Conversely, 4 RTX treatments were unsuccessful, with patients requiring chronic hemodialysis within 1 year. The urinary albumin-to-protein ratio before treatment was predictive of renal response. Immunological remission occurred after 11 treatment courses and was associated with clinical response in 10 of 11 patients. Three patients experienced severe adverse events. CONCLUSION: RTX seems effective and reasonably safe in PLA2R-associated membranous nephropathy with stage 4 or 5 chronic kidney disease. Immunological remission is associated with a good clinical outcome.

Renal involvement in lysinuric protein intolerance: contribution of pathology to assessment of heterogeneity of renal lesions.

Lysinuric protein intolerance (LPI) is a rare autosomal recessive disease caused by mutations in the SLC7A7 gene encoding the light subunit of a cationic amino acid transporter. Symptoms mimic primary urea cycle defects but dysimmune symptoms are also described. Renal involvement in LPI was first described in the 1980s. In 2007, it appeared that it could concern as much as 75% of LPI patients and could lead to end-stage renal disease. The most common feature is proximal tubular dysfunction and nephrocalcinosis but glomerular lesions are also reported. However, very little is known regarding histological lesions associated with LPI. We gathered every kidney biopsy of LPI-proven patients in our highly specialized pediatric and adult institution. Clinical, biological, and histological information was analyzed. Five LPI patients underwent kidney biopsy in our institution between 1986 and 2015. Clinically, 4/5 presented with proximal tubular dysfunction and 3/5 with nephrotic range proteinuria. Histology showed unspecific tubulointerstitial lesions and nephrocalcinosis in 3/5 biopsies and marked peritubular capillaritis in one child. Glomerular lesions were heterogeneous: lupus-like-full house membranoproliferative glomerulonephritis (MPGN) in one child evolved towards monotypic IgG1κ MPGN sensitive to immunomodulators. One patient presented with glomerular non-AA non-AL amyloidosis. Renal biopsy is particularly relevant in LPI presenting with glomerular symptoms for which variable histological lesions can be responsible, implying specific treatment and follow-up.