Genetic Analyses in Dent Disease and Characterization of CLCN5 Mutations in Kidney Biopsies.

Dent disease (DD), an X-linked renal tubulopathy, is mainly caused by loss-of-function mutations in CLCN5 (DD1) and OCRL genes. CLCN5 encodes the ClC-5 antiporter that in proximal tubules (PT) participates in the receptor-mediated endocytosis of low molecular weight proteins. Few studies have analyzed the PT expression of ClC-5 and of megalin and cubilin receptors in DD1 kidney biopsies. About 25% of DD cases lack mutations in either CLCN5 or OCRL genes (DD3), and no other disease genes have been discovered so far. Sanger sequencing was used for CLCN5 gene analysis in 158 unrelated males clinically suspected of having DD. The tubular expression of ClC-5, megalin, and cubilin was assessed by immunolabeling in 10 DD1 kidney biopsies. Whole exome sequencing (WES) was performed in eight DD3 patients. Twenty-three novel CLCN5 mutations were identified. ClC-5, megalin, and cubilin were significantly lower in DD1 than in control biopsies. The tubular expression of ClC-5 when detected was irrespective of the type of mutation. In four DD3 patients, WES revealed 12 potentially pathogenic variants in three novel genes (SLC17A1, SLC9A3, and PDZK1), and in three genes known to be associated with monogenic forms of renal proximal tubulopathies (SLC3A, LRP2, and CUBN). The supposed third Dent disease-causing gene was not discovered.

Pilot cohort study on the potential role of TCF7L2 rs7903146 on ischemic heart disease among non-diabetic kidney transplant recipients.

BACKGROUND: TCF7L2 rs7903146 C>T polymorphism is associated with diabetes in the general population but its independent impact on cardiovascular disease is debated. On this basis, we investigated its association with major adverse cardiac events (MACE) in a single-center cohort of non-diabetic kidney transplant recipients (KTRs). METHODS: Patients with pretransplant diabetes were excluded and patients who developed post-transplant diabetes were censored at time of diagnosis. RESULTS: rs7903146 C>T polymorphism appeared to modulate the risk of MACE: 5-year prevalence was 0.8% in CC patients, 7.2% in CT patients and 9.7% in TT patients (P<.001). TCF7L2 rs7903146 was an independent predictor of MACE in a multivariate Cox regression model (for each T allele, HR: 2.99, 95%CI: 1.62-5.52, P<.001), together with history of cardiac ischemic events (HR: 8.69, 95%CI: 3.57-21.16, P<.001), DGF (HR: 2.42, 95%CI: 0.98-5.95, P=.056) and HLA-mismatches (for each mismatch: HR: 1.55, 95%CI: 1.00-2.43, P=.053). Introduction of rs7903146 C>T polymorphism into a model based on these clinical variables significantly increased predictive power for MACE (P=.003). CONCLUSIONS: TCF7L2 rs7903146 T allele may be strongly and independently associated with MACE in non-diabetic KTRs. These findings suggest the possibility of employing this SNP to more accurately stratify cardiological risk in KTRs.

De novo noncutaneous malignancies after kidney transplantation are associated with an increased risk of graft failure: results from a time-dependent analysis on 672 patients.

The aim of this study was to evaluate the association between cancer occurrence and risk of graft failure in kidney transplant recipients. From November 1998 to November 2013, 672 adult patients received their first kidney transplant from a deceased donor and had a minimum follow-up of 6 months. During a median follow-up of 4.7 years (3523 patient-years), 47 patients developed a nonmelanoma skin cancer (NMSC) and 40 a noncutaneous malignancy (NCM). A total of 59 graft failures were observed. The failure rate was 6 per 100 patient-year (pt-yr) after NCM versus 1.5 per 100 pt-yr in patients without NCM. In a time-dependent multivariable model, the occurrence of NCM appeared to be associated with failure (HR = 3.27; 95% CI = 1.44-7.44). The effect of NCM on the cause-specific graft failure was different (P = 0.002) when considering events due to chronic rejection (HR = 0.55) versus other causes (HR = 15.59). The reduction of the immunosuppression after NCM was not associated with a greater risk of graft failure. In conclusion, our data suggest that post-transplant NCM may be a strong risk factor for graft failure, particularly for causes other than chronic rejection.

Erdheim-Chester Disease as a Mimic of IgG4-Related Disease: A Case Report and a Review of a Single-Center Cohort.

Immunoglobulin-G4 (IgG4)-related disease (IgG4RD) is a fibro-inflammatory disorder characterized by tissue-infiltrating IgG4 plasma cells, and, often, high serum IgG4. Several autoimmune, infectious, or proliferative conditions mimic IgG4RD. Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytosis, characterized by foamy histiocytic infiltration, fibrosis, and chronic inflammation. ECD and IgG4RD manifestations may overlap.A patient presented with huge fibrous retroperitoneal masses causing compression on neighboring structures; the case posed the challenge of the differential diagnosis between IgG4RD and ECD mainly because of a prominent serum and tissue IgG4 response.Retroperitoneal biopsy led to the diagnosis of ECD; the V600E BRAF mutation was found. Treatment with the BRAF inhibitor vemurafenib was started.Treatment failed to induce mass regression and the patient died after 3 months of therapy. Prompted by this case, we examined serum and tissue IgG4 in a series of 15 ECD patients evaluated at our center, and found that approximately one-fourth of the cases have increased IgG4 in the serum and often in the tissue.The differential diagnosis between IgG4RD and ECD can be challenging, as some ECD patients have prominent IgG4 responses. This suggests the possibility of common pathogenic mechanisms between ECD and IgG4RD.

Testing for the cytosine insertion in the VNTR of the MUC1 gene in a cohort of Italian patients with autosomal dominant tubulointerstitial kidney disease.

INTRODUCTION: Medullary cystic kidney disease type 1 (MCKD1; OMIM #174000) is a familial progressive tubule-interstitial nephropathy belonging to the recently defined group of autosomal dominant tubulointerstitial kidney diseases (ADTKD). CASE REPORT: A specific type of cytosine insertion in the extracellular variable number tandem repeat (VNTR) domain of the MUC1 gene causing the disease was tested in a group of 21 families with ADTKD. We identified this type of MUC1 mutation in two families, whose affected members are described in detail in this case report. Affected (ADTKD-MUC1) members developed end-stage renal disease (ESRD) with a higher incidence (p = 0.033) and at a younger age (p = 0.013) than probands with ADTKD but without this type of mutation. All patients with MUC1-associated kidney disease shared a rather unspecific tubule-interstitial laboratory pattern without medullary cysts, leading to ESRD between the age of 33 and 47 years. We were not able to identify any single common extra-renal feature among affected patients, even if they had various comorbidities, which are described in detail. CONCLUSIONS: We identified this type of MUC1 mutation in 9.5 % of families from an ADTKD Italian cohort; larger studies are needed to better define the criteria for genetic testing for this type of mutation.

The Role of TCF7L2 rs7903146 in Diabetes After Kidney Transplant: Results From a Single-Center Cohort and Meta-Analysis of the Literature.

BACKGROUND: Several genetic polymorphisms modulate the risk of posttransplant diabetes mellitus (PTDM), a complication associated with an increased morbidity and mortality after kidney transplantation; however, their clinical utility is still undefined. METHODS: Genetic analysis was performed in 464 kidney transplantation recipients to evaluate whether transcription factor 7-like 2 (TCF7L2) rs7903146 gene polymorphism is associated with the risk of PTDM and a meta-analysis of similar studies including our results was performed (total kidney transplantation recipients, n = 3105). A predictive model of PTDM was built on the basis of this polymorphism and clinical parameters. RESULTS: In our cohort, 163 patients possessed the CC genotype of rs7903146 (35.1%), 237 were CT (51.1%), and 64 were TT (13.8%): their 2 years PTDM incidence was, respectively, 7.8%, 11.9%, and 22.7%. At multivariate analysis, age (per year; hazard ratio [HR], 1.029; 95% confidence interval [95% CI], 1.005-1.054; P = 0.017), body mass index (25.0-29.9 vs <25.0; HR, 2.43; 95% CI, 1.40-4.23; P = 0.0018; ≥30 vs <25.0; HR, 5.70; 95% CI, 2.77-11.74; P < 0.0001), TCF7L2 rs7903146 (per each T allele; HR, 1.81; 95% CI, 1.26-2.59; P = 0.001) and previous transplants (HR, 2.80; 95% CI, 1.39-5.64; P = 0.004) emerged as independent predictive factors for PTDM.Meta-analysis of present and 5 previous studies showed higher risk of PTDM in carriers of rs7903146 TT genotype (odds ratio, 1.95; 95% CI, 1.39-2.74; P < 0.0001) and absence of heterogeneity among studies (I = 0%).Inclusion of this polymorphism in a predictive model appeared to improve its ability to stratify patients according to the risk of PTDM. CONCLUSIONS: In renal transplant patients, TCF7L2 rs7903146 is strongly and independently associated with PTDM and might hold the potential to identify patients at risk for this complication.

Impact of pre-transplant antiaggregant and anticoagulant therapies on early hemorrhagic and cardiovascular events after kidney transplantation.

BACKGROUND: Oral anticoagulation with vitamin K antagonists (VKA) and antiaggregant therapy (AAT) are common among dialysis patients, but it is not known if they increase the risk of hemorrhagic (HE) or cardiovascular events (CVE) in the early post-transplant weeks. METHODS: We conducted a retrospective analysis on 911 consecutive kidney transplants (KTxs) in order to analyze the impact of AAT and VKA on early HE and CVE-which might be related to their withdrawal-and to identify the main risk factors for these complications. RESULTS: We observed 21/911 HE (2.3%; 1 death, 4 allograft loss); risk factors for HE at multivariate analysis were: KTx before 2004 (when anti-factor Xa activity measurement was not available; odds ratio, OR 5.835, [95% confidence interval, 1.241-27.436], p = 0.026), and VKA (OR 7.090 [2.030-24.772], p = 0.002), while AAT was not a risk factor. CVE were 32/911 (3.5%; 3 deaths, 11 allograft loss): risk factors for CVE at multivariate analysis were: previous cardiovascular events (OR 4.180 [1.615-10.948], p = 0.0032) and cinacalcet use (OR 7.930 [3.002-20.945], p < 0.0001), while neither VKA nor AAT had any impact. CONCLUSIONS: In conclusion, HE and CVE are relatively rare but can be severe, but there are no pre-KTx modifiable risk factors. If an anticoagulant therapy with low molecular weight heparins has to be started soon after surgery, monitoring of anti-Xa activity is highly recommended.

Circulating suPAR levels are affected by glomerular filtration rate and proteinuria in primary and secondary glomerulonephritis.

BACKGROUND: Circulating levels of soluble urokinase-like plasminogen activator receptor (suPAR) have been associated with proteinuria and renal function in focal segmental glomerulosclerosis (FSGS). This study aimed to evaluate if circulating suPAR levels are independently associated with proteinuria in patients with non-FSGS glomerulonephritis. METHODS: This is a cross-sectional analysis of suPAR levels on 42 patients with primary non-FSGS glomerulonephritis (group GN) and 140 patients with secondary glomerulonephritis within an autoimmune disease (group AID). RESULTS: suPAR serum levels were significantly higher in AID patients (4,733 ± 3,073 pg/ml) than in healthy controls (1,908 ± 1,685 pg/ml; p < 0.001), whereas GN patients displayed intermediate levels (3,670 ± 2,435 pg/ml; p = 0.021). Multivariate analysis for elevated serum suPAR (>3,000 pg/ml) showed an independent association with estimated glomerular filtration rate (eGFR) <60 ml/min/1.73 m(2) [odds ratio (OR) = 4.19, 95% confidence interval (CI): 1.67-10.54, p = 0.002], proteinuria >0.5 g/day (OR = 2.97; 95% CI: 1.32-6.70; p = 0.009) and presence of secondary vs. primary GN (OR = 2.87, 95% CI: 1.25-6.23; p = 0.013). A general linear model confirmed that suPAR levels were significantly affected by proteinuria >0.50 g/day (coefficient +1,477 pg/ml), eGFR (-38 pg/ml per 1 ml/min/1.73 m(2) increase) and presence of secondary vs. primary GN (+1,368 pg/ml). CONCLUSIONS: This study shows that elevated serum suPAR levels are associated with reduced eGFR and presence of proteinuria in both primary and secondary GN, suggesting that circulating suPAR may represent a common biomarker of renal involvement in a wide spectrum of GN.

Calcium-sensing-related gene mutations in hypercalcaemic hypocalciuric patients as differential diagnosis from primary hyperparathyroidism: detection of two novel inactivating mutations in an Italian population.

BACKGROUND: Inactivating mutations of the calcium-sensing receptor (CaSR), of the G-protein subunit α11 (GNA11) and of the adaptor-related protein complex 2, sigma 1 subunit (AP2S1) genes are responsible for familial hypocalciuric hypercalcaemia (FHH). The aim of this study was to analyse prevalence and pathogenicity of CaSR, GNA11 and AP2S1 mutations in patients with an FHH phenotype and to compare them with a sample of patients with primary hyperparathyroidism (PHPT) in order to identify the most useful laboratory parameter for a differential diagnosis. METHODS: Patients with an FHH phenotype were studied with polymerase chain reaction amplification and direct sequencing of the entire CaSR, GNA11 and AP2S1 coding sequences. Novel mutations were introduced in a Myc-tagged human wild-type (WT) CaSR cDNA-expressing vector, and functional assay was performed on human embryonic kidney cells evaluating expression and function of mutated proteins. RESULTS: Among 16 FHH patients, none had an inactivating GNA11 or AP2S1 mutation while 3 (18.8%) carried a CaSR mutation and 10 (62.5%) at least one CaSR polymorphism. Within the latter group, 7 of 10 patients had more than one polymorphism (4.1 ± 2.1 per patient). Two novel CaSR mutations [c.2120A>T (E707V) and c.2320G>A (G774S)] were identified: the E707V mutation prevented CaSR expression (western blot), whereas the G774S mutation determined a reduced receptor sensitivity to calcium (IP3 assay). PHPT patients showed significantly (P < 0.001) higher serum calcium, parathyroid hormone, urinary calcium and calcium-creatinine clearance ratio (CCCR) and significantly lower serum phosphate than FHH ones. CONCLUSIONS: FHH should be clearly differentiated by PHPT to avoid unnecessary surgery: CCCR could be a useful screening tool while genetic analysis should include the two novel CaSR mutations herein described. The role of multiple polymorphisms deserves further investigation in patients with an FHH phenotype.

Unexpectedly high prevalence of rare genetic disorders in kidney transplant recipients with an unknown causal nephropathy.

BACKGROUND: Patients with a rare genetic disease may receive renal transplantation (KTx) without a correct diagnosis of causal nephropathy and therefore develop unexpected and even severe complications. The aim of the study was to describe the cases of rare genetic disorders diagnosed after KTx, in order to draw clinical lessons for the transplant physician. METHODS: We retrospectively assessed all patients who had received a diagnosis of a rare genetic disorder after KTx. RESULTS: In our center, more than 30% (278/911) of kidney transplant (KTx) recipients were diagnosed with a causal nephropathy: Prevalence of rare genetic disorders in this group was 4.32% (12/278), including 2,8-dihydroxyadeninuria (2,8-DHA) disease (n = 2), HNF-1B-associated nephropathy (n = 2), UMOD-related nephropathy (n = 5), Fabry disease (n = 1), INF2 focal segmental glomerulosclerosis (n = 1), and Senior-Løken syndrome (n = 1). 2,8-DHA nephropathy relapsed in both patients causing an acute renal failure and jeopardizing the graft. CONCLUSIONS: Kidney transplant recipients without a diagnosis of causal nephropathy appear to be a selected population in which rare genetic diseases might be more common than expected. As even a belated diagnosis after KTx can have a significant impact on graft and patient survival and on other family members, this possibility should be evaluated in KTx recipients without a known causal nephropathy.

Osteopontin circulating levels correlate with renal involvement in systemic lupus erythematosus and are lower in ACE inhibitor-treated patients.

Elevated serum levels of osteopontin have been associated with cardiovascular disease, diabetic nephropathy, and autoimmune disease activity. Aim of the study was to investigate the relationship between osteopontin serum levels and renal damage in a population of patients with systemic lupus erythematosus (SLE). Osteopontin serum levels were analyzed in 101 SLE patients and compared to those of 115 healthy controls. Associations between osteopontin levels and renal involvement, disease activity and damage index, biochemical parameters, and therapy were assessed. Overall osteopontin serum levels were higher in SLE patients (median, 17.93 ng/mL; interquartile range, 8.13-35.07 ng/mL) than in healthy controls (median, 5.62 ng/mL; interquartile range, 2.61-13.83 ng/mL). Univariate logistic analysis among cases showed that high osteopontin levels (higher vs medium-lower tertile) were associated with renal involvement (p = 0.012), renal function (p = 0.007), proteinuria (p = 0.011), anemia (p < 0.001), and SLICC/ACR Damage Index (p < 0.001). Multivariate analysis showed an independent association between high osteopontin serum levels (higher vs medium-lower tertile) and chronic kidney disease (OR = 4.89; 95 % CI, 1.24-19.24; p = 0.008), proteinuria (OR = 4.56; 95 % CI, 1.15-18.04; p = 0.027), anemia (OR = 4.66; 95 % CI, 1.25-17.43; p = 0.008), and use of renin-angiontensin system antagonists (OR = 0.234; 95 % CI, 0.06-0.98; p = 0.047). This study shows that elevated osteopontin serum levels significantly correlate with renal involvement and anemia in SLE. Moreover, it suggests that renin-angiontensin system antagonists decrease osteopontin levels-this effect is consistent with the inhibitory effect of these drugs on osteopontin renal expression, detected in animal models by other authors, and may provide a new rationale for their employment.

New trends of an old disease: the acute post infectious glomerulonephritis at the beginning of the new millenium.

The association between acute renal disease and infection has been known since the mid '800s: acute post-infectious glomerulonephritis (PIGN) is a reactive immunological process against the kidney secondary to an infection, classically caused by a Streptococcus. The typical clinical presentation of PIGN is an acute nephritic syndrome with macro- or microscopic hematuria, proteinuria, hypertension, edema and renal function impairment of variable degree. The histology is characterized by an intracapillary glomerular proliferation, but may rarely be associated with an extracapillary proliferation. The classical childhood form is still present nowadays, even with severe cases, in developing countries, while in the last decades it almost disappeared in industrialized countries, where post-infectious GN are often found in elderly patients with multiple comorbidities. These clinical variants are usually related to other infective agents, like Staphylococcus aureus, both methicillin resistant (MRSA) and susceptible, and may be characterized by an IgA-dominant deposition. Kidney biopsy is rarely needed, especially in the child, while in the adult or old patient a biopsy is warranted if there is an atypical presentation or evolution, like rapidly progressive renal failure, absent or delayed function recovery, persisting low C3, nephrotic range proteinuria and persisting high proteinuria. Current therapy strategies rely on culture-guided systemic antibiotics, especially in the old patient, in which MRSA are relatively frequent, support therapy and only in very selected cases on steroids. These latter cases include the rare PIGN with crescents and those with a severe interstitial inflammation.

Chronic renal failure of unknown origin is caused by HNF1B mutations in 9% of adult patients: a single centre cohort analysis.

BACKGROUND: HNF1B gene mutations might be an underdiagnosed cause of nephropathy in adult patients mainly because of their pleomorphic clinical presentations. As most studies are based on paediatric populations, it is difficult to assess the likelihood of finding HNF1B mutations in adult patients and consequently define clinical settings in which genetic analysis is indicated. The aim of this study was the search for mutations in the HNF1B gene in a cohort of unrelated adult patients with nephropathy of unknown aetiology. METHODS: Patients were tested for the HNF1B gene if they had chronic kidney disease of unknown origin and renal structure abnormalities (RSA) or a positive family history of nephropathy. The HNF1B coding sequence and intron-exon boundaries were analysed by direct sequencing. The search for gene deletions was performed by Multiple Ligation Probe Analysis (MLPA). RESULTS: Heterozygous mutations were identified in 6 out of 67 screened patients (9.0%) and included two whole gene deletions, one nonsense (p.Gln136Stop), two missense (p.Gly76Cys and p.Ala314Thr) mutations and a frameshift microdeletion (c.384_390 delCATGCAG), the latter two (c.384_390 del and p.Ala314Thr) not ever being reported to date. Mean age of the mutated patients at screening was 48.5 years with a M/F ratio of 2/4. The clinical manifestations of affected patients were extremely pleomorphic, including several urological and extra-renal manifestations. CONCLUSIONS: Mutations of HNF1B could explain chronic kidney disease in up to 9% of adult patients with a nephropathy of unknown aetiology and RSA: therefore an HNF1B mutation analysis should be considered in this group of patients.

Peritoneal ultrafiltration in refractory heart failure: a cohort study.

INTRODUCTION: Acutely decompensated heart failure (HF) in patients with diuretic resistance is often treated with extracorporeal ultrafiltration. Peritoneal ultrafiltration (PUF) has been proposed for the long-term management of severe HF after resolution of the acute episode. The aim of the present study was to evaluate the use of PUF in the treatment of chronic refractory HF in patients without end-stage renal disease. ♢ METHODS: This multicenter (10 nephrology departments throughout Italy) retrospective observational study included patients with severe HF refractory to maximized drug treatment. The patients were proposed for PUF because they had experienced at least 3 hospital admissions in the preceding year for acutely decompensated HF requiring extracorporeal ultrafiltration. ♢ RESULTS: Of the 48 study patients (39 men, 9 women; mean age 74 ± 9 years), 30 received 1 nocturnal icodextrin exchange, 5 required 2 daily exchanges, and 13 received 2 - 4 sessions per week of automated peritoneal dialysis. During the first year, renal function remained stable (initial: 20.8 ± 10.0 mL/min/1.73 m(2); end: 22.0 ± 13.6 mL/min/1.73 m(2)), while pulmonary artery systolic pressure declined to 40 ± 6.09 mmHg from 45.5 ± 9.18 mmHg (p = 0.03), with a significant concomitant improvement in New York Heart Association functional status. Hospitalizations decreased to 11 ± 17 days/patient-year from 43 ± 33 days/patient-year before the start of PUF (p < 0.001). The incidence of peritonitis was 1 episode in 45 patient-months. Patient survival was 85% at 1 year and 56% at 2 years. ♢ CONCLUSIONS: This study confirms the satisfactory results of using PUF for chronic HF in elderly patients.