Activation of the acute inflammatory phase response in idiopathic nephrotic syndrome: association with clinicopathological phenotypes and with response to corticosteroids

Glomeruloesclerosis; Inflamación; Síndrome nefróticoGlomerulosclerosis; Inflammation; Nephrotic syndromeGlomeruloesclerosi; Inflamació; Síndrome nefròticaBackground Data on the activation of the acute inflammatory response and its clinicopathological associations in idiopathic nephrotic syndrome (INS) are scarce and discordant. Objective To analyse the associations between the activation of the inflammatory response, the clinicopathological characteristics of disease and the response to treatment with steroids in patients with INS. Methods A total of 101 patients with INS due to minimal change disease (MCD; n = 44), focal segmental glomerulosclerosis (FSGS; n = 33) and membranous nephropathy (MN; n = 24) and 50 healthy controls were included. At diagnosis, we measured the levels of haemopexin (Hx), haptoglobin (Hgl), interleukin-6 (IL-6), soluble urokinase-type plasminogen activator receptor (suPAR), tumour necrosis factor-α (TNF-α), soluble IL-1 receptor, interferon-γ and C-reactive protein. We analysed their clinicopathological associations. In MCD and FSGS patients, we determined the association between the levels of these variables and steroid resistance. Results The levels of Hx, Hgl, TNF-α, suPAR and IL-6 were higher in patients with INS than in healthy controls, and were not associated with proteinuria, estimated glomerular filtration rate or serum albumin. In MCD and FSGS patients, Hx, Hgl, IL-6 and TNF-α levels were similar and significantly higher than in MN patients. In patients with MCD and FSGS, multivariate analyses identified FSGS and the levels of Hx, Hgl or IL-6 as independent predictors of steroid resistance. Conclusions The activation of the inflammatory response in patients with INS is heterogeneous and more prevalent in MCD or FSGS patients than in those with MN. In MCD and FSGS, elevated levels of Hx, Hgl or IL-6 are independently associated with steroid resistance

Poor phenotype-genotype association in a large series of patients with Type III Bartter syndrome

Excreció; Genètica humana; MutacióExcreción; Genética humana; MutaciónExcretion; Human genetics; MutationIntroduction Type III Bartter syndrome (BS) is an autosomal recessive renal tubule disorder caused by loss-of-function mutations in the CLCNKB gene, which encodes the chloride channel protein ClC-Kb. In this study, we carried out a complete clinical and genetic characterization in a cohort of 30 patients, one of the largest series described. By comparing with other published populations, and considering that 80% of our patients presented the p.Ala204Thr Spanish founder mutation presumably associated with a common phenotype, we aimed to test the hypothesis that allelic differences could explain the wide phenotypic variability observed in patients with type III BS. Methods Clinical data were retrieved from the referral centers. The exon regions and flanking intronic sequences of the CLCNKB gene were screened for mutations by polymerase chain reaction (PCR) followed by direct Sanger sequencing. Presence of gross deletions or duplications in the region was checked for by MLPA and QMPSF analyses. Results Polyuria, polydipsia and dehydration were the main common symptoms. Metabolic alkalosis and hypokalemia of renal origin were detected in all patients at diagnosis. Calciuria levels were variable: hypercalciuria was detected in 31% of patients, while 23% had hypocalciuria. Nephrocalcinosis was diagnosed in 20% of the cohort. Two novel CLCNKB mutations were identified: a small homozygous deletion (c.753delG) in one patient and a small deletion (c.1026delC) in another. The latter was present in compound heterozygosis with the already previously described p.Glu442Gly mutation. No phenotypic association was obtained regarding the genotype. Conclusion A poor correlation was found between a specific type of mutation in the CLCNKB gene and type III BS phenotype. Importantly, two CLCNKB mutations not previously described were found in our cohortThis study was supported by two grants (PI09/90888 and PI11/01412) from the FIS of the Instituto de Salud Carlos III, Madrid, Spain, the Department of Health of the Basque Government (2014111064), and the Department of Education of the Basque Government (IT795-13)

CD44-negative parietal–epithelial cell staining in minimal change disease: association with clinical features, response to corticosteroids and kidney outcome

Idiopathic nephrotic syndrome; Minimal change disease; Parietal–epithelial cellsSíndrome nefrótico idiopático; Enfermedad de cambios mínimos; Células parietales-epitelialesSíndrome nefròtica idiopàtica; Malaltia de canvis mínims; Cèl·lules parietals-epitelialsBackground Activation of parietal–epithelial cells (PECs) with neo-expression of CD44 has been found to play a relevant role in the development of focal and segmental glomerulosclerosis (FSGS). The aim of this study was to analyse whether the expression of CD44 by PECs in biopsies of minimal change disease (MCD) is associated with the response to corticosteroids, with kidney outcomes and/or can be considered an early sign of FSGS. Methods This multicentric, retrospective study included paediatric and adult patients with MCD. Demographic, clinical and biochemical data were recorded, and biopsies were stained with anti-CD44 antibodies. The association between PECs, CD44 expression and the response to corticosteroids, and kidney outcomes were analysed using logistic, Kaplan–Meier and Cox regression analyses. Results A total of 54 patients were included: 35 (65%) <18 years and 19 (35%) adults. Mean follow-up was 68.3 ± 37.9 months. A total of 19/54 patients (35.2%) showed CD44-positive staining. CD44-positive patients were younger (14.5 ± 5 versus 21.5 ± 13, P = 0.006), and showed a higher incidence of steroid-resistance [11/19 (57.8%) versus 7/35 (20%), P = 0.021; odds ratio: 5.5 (95% confidence interval 1.6–18), P = 0.007] and chronic kidney disease [9/19 (47.3%) versus 6/35 (17.1%), P = 0.021; relative risk: 3.01 (95% confidence interval 1.07–8.5), P = 0.037]. Follow-up re-biopsies of native kidneys (n = 18), identified FSGS lesions in 10/12 (83.3%) of first-biopsy CD44-positive patients versus 1/6 (16.7%) of first-biopsy CD44-negative patients (P = 0.026). Conclusions In patients with a light microscopy pattern of MCD, CD44-positive staining of PECs is associated with a higher prevalence of steroid resistance and worse kidney outcomes, and can be considered an early sign of FSGS.C.M. is supported by a Miguel Servet grant, Fondo de investigación sanitaria, Instituto de Salud Carlos III, Ministerio de Ciencia, Innovacio´n y Universidades [CP18/00116]. No additional funding was required for the current study

Identification of a Locus on the X Chromosome Linked to Familial Membranous Nephropathy

Introduction: Membranous nephropathy (MN) is the most common cause of nephrotic syndrome (NS) in adults and is a leading cause of end-stage renal disease due to glomerulonephritis. Primary MN has a strong male predominance, accounting for approximately 65% of cases; yet, currently associated genetic loci are all located on autosomes. Previous reports of familial MN have suggested the existence of a potential X-linked susceptibility locus. Identification of such risk locus may provide clues to the etiology of MN. Methods: We identified 3 families with 8 members affected by primary MN. Genotyping was performed using single-nucleotide polymorphism microarrays, and serum was sent for anti-phospholipase A2 receptor (PLA2R) antibody testing. All affected members were male and connected through the maternal line, consistent with X-linked inheritance. Genome-wide multipoint parametric linkage analysis using a model of X-linked recessive inheritance was conducted, and genetic risk scores (GRSs) based on known MN-associated variants were determined. Results: Anti-PLA2R testing was negative in all affected family members. Linkage analysis revealed a significant logarithm of the odds score (3.260) on the short arm of the X chromosome at a locus of approximately 11 megabases (Mb). Haplotype reconstruction further uncovered a shared haplotype spanning 2 Mb present in all affected individuals from the 3 families. GRSs in familial MN were significantly lower than in anti-PLA2R–associated MN and were not different from controls. Conclusions: Our study identifies linkage of familial membranous nephropathy to chromosome Xp11.3-11.22. Family members affected with MN have a significantly lower GRS than individuals with anti-PLA2R–associated MN, suggesting that X-linked familial MN represents a separate etiologic entity