Podocyte Antigen Staining to Identify Distinct Phenotypes and Outcomes in Membranous Nephropathy: A Retrospective Multicenter Cohort Study.

RATIONALE & OBJECTIVE: Membranous nephropathy (MN) is characterized by the deposition of immune complexes along glomerular basement membranes. M-Type phospholipase A2 receptor (PLA2R), thrombospondin type 1 domain-containing 7A (THSD7A), exostosin 1 and 2 (EXT1/2), and neural epidermal growth factor-like 1 protein (NELL-1) have been identified as established or potential podocyte antigens in MN. We investigated the association of podocyte antigen staining with MN clinical phenotype and outcomes. STUDY DESIGN: Multicenter retrospective cohort study. SETTING & PARTICIPANTS: 177 consecutive patients with MN unrelated to lupus erythematosus, identified after screening of 3,875 native kidney biopsies performed in the Belgian UCLouvain Kidney Disease Network from 2000 through 2018. PREDICTOR: Positive immunostaining for podocyte antigens on archived kidney biopsy samples. OUTCOMES: Association with different phenotypes (baseline characteristics of patients and pathologic findings on kidney biopsy), time to cancer and to kidney failure. ANALYTICAL APPROACH: Kaplan-Meier estimates and Cox regression analyses to assess time to cancer and kidney failure. RESULTS: 177 patients were followed up for a median of 4.0 (IQR, 1.3-8.0) years. Diagnosis of PLA2R-positive (PLA2R+), THSD7A+, and double-negative (PLA2R-/THSD7A-) MN was made in 117 (66.1%), 6 (3.4%), and 54 (30.5%) patients, respectively. Progression to kidney failure was similar in all groups. Although the number of patients with THSD7A+MN was small, they showed a higher incidence (50%) and increased risk for developing cancer during follow-up (adjusted HR, 5.0 [95% CI, 1.4-17.9]; P=0.01). 8% and 5% of patients with double-negative MN stained positively for EXT1/2 and NELL-1, respectively. Most patients with EXT1/2+MN were women, had features of systemic autoimmunity, and showed glomerular C1q deposits. LIMITATIONS: Retrospective design; small number of patients in the THSD7A group; lack of evaluation of immunoglobulin G subclasses deposition. CONCLUSIONS: Our real-world data describe the relative prevalence of subgroups of MN and support the hypothesis that a novel classification of MN based on podocyte antigen staining may be clinically relevant.

Clinical and mutational spectrum of hypoparathyroidism, deafness and renal dysplasia syndrome.

BACKGROUND: Hypoparathyroidism, deafness and renal dysplasia (HDR) syndrome is a rare autosomal dominant disorder, secondary to mutations in the GATA-3 gene. Due to its wide range of penetrance and expressivity, the disease may not always be recognized. We herein describe clinical and genetic features of patients with HDR syndrome, highlighting diagnostic clues. METHODS: Medical records of eight patients from five unrelated families exhibiting GATA-3 mutations were reviewed retrospectively, in conjunction with all previously reported cases. RESULTS: HDR syndrome was diagnosed in eight patients between the ages of 18 and 60 years. Sensorineural deafness was consistently diagnosed, ranging from clinical hearing loss since infancy in seven patients to deafness detected only by audiometry in adulthood in one single patient. Hypoparathyroidism was present in six patients (with hypocalcaemia and inaugural seizures in two out of six). Renal abnormalities observed in six patients were diverse and of dysplastic nature. Three patients displayed nephrotic-range proteinuria and reached end-stage renal disease (ESRD) between the ages of 19 and 61 years, whilst lesions of focal and segmental glomerulosclerosis were histologically demonstrated in one of them. Interestingly, phenotype severity differed significantly between a mother and son within one family. Five new mutations of GATA-3 were identified, including three missense mutations affecting zinc finger motifs [NM_001002295.1: c.856A>G (p.N286D) and c.1017C>G (p.C339W)] or the conserved linker region [c.896G>A (p.R299G)], and two splicing mutations (c.924+4_924+19del and c.1051-2A>G). Review of 115 previously reported cases of GATA-3 mutations showed hypoparathyroidism and deafness in 95% of patients, and renal abnormalities in only 60%. Overall, 10% of patients had reached ESRD. CONCLUSIONS: We herein expand the clinical and mutational spectrum of HDR syndrome, illustrating considerable inter- and intrafamilial phenotypic variability. Diagnosis of HDR should be considered in any patient with hypoparathyroidism and deafness, whether associated with renal abnormalities or not. HDR diagnosis is established through identification of a mutation in the GATA-3 gene.

Epidemiology, Outcomes, and Complement Gene Variants in Secondary Thrombotic Microangiopathies.

BACKGROUND: The identification of complement defects as major drivers of primary atypical hemolytic uremic syndrome (HUS) has transformed the landscape of thrombotic microangiopathies (TMAs), leading to the development of targeted therapies and better patient outcomes. By contrast, little is known about the presentation, genetics, and outcomes of TMA associated with specific diseases or conditions, also referred to as secondary TMA. METHODS: In this study, we assessed the relative incidence, clinical and genetic spectra, and long-term outcomes of secondary TMA versus other TMAs in consecutive patients hospitalized with a first episode of TMA from 2009 to 2019 at two European reference centers. RESULTS: During the study period, 336 patients were hospitalized with a first episode of TMA. Etiologies included atypical HUS in 49 patients (15%), thrombotic thrombocytopenic purpura (TTP) in 29 (9%), shigatoxin-associated HUS in 70 (21%), and secondary TMA in 188 (56%). The main causes of secondary TMA were hematopoietic stem-cell transplantation ( n =56, 30%), solid-organ transplantation ( n =44, 23%), and malignant hypertension ( n =25, 13%). Rare variants in complement genes were identified in 32 of 49 patients (65%) with atypical HUS and eight of 64 patients (13%) with secondary TMA; pathogenic or likely pathogenic variants were found in 24 of 49 (49%) and two of 64 (3%) of them, respectively ( P < 0.001). After a median follow-up of 1157 days, death or kidney failure occurred in 14 (29%), eight (28%), five (7%), and 121 (64%) patients with atypical HUS, TTP, shigatoxin-associated HUS, and secondary TMA, respectively. Unadjusted and adjusted Cox regressions showed that patients with secondary TMA had the highest risk of death or kidney failure (unadjusted hazard ratio [HR], 3.35; 95% confidence interval [CI], 1.85 to 6.07; P < 0.001; adjusted HR, 4.11; 95% CI, 2.00 to 8.46; P < 0.001; considering atypical HUS as reference). CONCLUSIONS: Secondary TMAs represent the main cause of TMA and are independently associated with a high risk of death and progression to kidney failure.

Lessons for the clinical nephrologist: an uncommon cause of pulmonary-renal syndrome.

Pulmonary-renal syndrome refers to the combination of elevated plasma creatinine concentration and/or abnormal urinalysis with diffuse alveolar hemorrhage, and involves both an urgent diagnostic approach and care. We report the case of a 24-year-old man presenting with diffuse alveolar hemorrhage as well as a nephritic syndrome associating kidney failure, moderate hypertension, hematuria and selective glomerular proteinuria. The initial high suspicion of anti-glomerular basement membrane (GBM) disease or ANCA-associated vasculitis justified intravenous pulse-corticotherapy in association with plasma exchange. Renal biopsy was remarkable for an IgA nephropathy, lesions of active thrombotic microangiopathy (TMA) and a positive staining for complement factor C4d. Because anti-GBM and ANCA antibodies returned negative, plasma exchange was discontinued, but oral corticosteroids were maintained to prevent alveolar hemorrhage recurrence. In the absence of renal function recovery, hemodialysis was initiated. TMA lesions are frequently seen in IgA nephropathy and are associated with a poorer prognosis. Complement activation seems to be involved in the development of those lesions and contributes to disease progression. Conversely, alveolar hemorrhage in the setting of IgA nephropathy is uncommon. It is thought to result from non-specific mucosal hemorrhage, an immune complex mediated basement membrane damage and an IgA-mediated capillaritis against basement membrane antigens.

Eliminating Hepatitis C Virus From a Prevalent Kidney Transplant Recipient Population: A Single-Center Study in Belgium in the Direct-Acting Antivirals Era.

BACKGROUND: Direct-acting antivirals (DAAs) have revolutionized the treatment of hepatitis C virus (HCV) infection. Although previous studies have reported positive results with DAAs after kidney transplantation (KT), their impact on the prevalence of HCV viremia (HCVv) in prevalent kidney transplant recipients (KTRs) remains ill defined. METHODS: We retrospectively reviewed the HCV status of all patients followed at Cliniques Universitaires Saint-Luc, Brussels, Belgium, outpatient KT clinic between January 2014 and December 2018. We collected the clinical features of KTRs treated with DAAs during this period and calculated the annual prevalence of HCVv over this period. RESULTS: Out of 1451 KTRs, 22 (1.52%) had HCVv in 2014 to 2018. From 2014 to 2018, the annual prevalence of HCVv dropped from 1.97% to 0.43%, (P < .001). Fourteen KTRs were treated with DAAs a median of 197 months (range: 5-374) after KT, mostly (79%) in 2017 after reimbursement restrictions of DAAs for KTRs in Belgium were removed. DAA treatment was safe with a sustained virological response rate at 12 weeks after treatment (SVR12) of 93%. Two patients died 14 months (lymphoma, despite SVR12) and 7 months (hepatocarcinoma, no SVR12) after DAAs initiation, respectively. Among HCVv KTRs not treated with DAAs (n = 8), 2 lost their graft, 5 died, and 1 is initiating therapy. The current prevalence of HCVv in the cohort is 0.08%, with a single patient currently on treatment. CONCLUSION: Treatment with DAAs led to a dramatic decrease of HCVv prevalence in this KTR cohort. DAA use was safe and effective. Elimination of HCV is possible at KT clinics.

Onco-nephrology: glomerular diseases with cancer.

Glomerular diseases occurring in the course of malignancies remain rare. Diverse glomerular lesions can be observed in a variety of neoplasms and involve different pathophysiologic links between the glomerulopathy and the cancer. The pathophysiology of solid tumor-associated glomerulopathies remains obscure, whereas in hematologic malignancy-induced paraneoplastic glomerulopathies, a molecular link can usually be demonstrated. The aim of this review is to provide an update on glomerular diseases associated with carcinoma and hematologic malignancies, covering epidemiology, pathophysiology, clinical presentation, and therapy. Special emphasis will be placed on the potential usefulness of novel biomarkers, such as antiphospholipase A2 receptor antibodies, for the diagnosis of membranous nephropathy, and on new associations and recent entities, including (proliferative) GN with nonorganized monoclonal immunoglobulin deposits and myeloproliferative neoplasm-related glomerulopathy.