The Heart of Children with Steroid-Resistant Nephrotic Syndrome: Is It All Podocin?

The Genetics of Canine Pulmonary Valve Stenosis

There have been recent advancements in understanding the genetic contribution to pulmonary valve stenosis (PS) in brachycephalic breeds such as the French Bulldog and Bulldog. The associated genes are transcriptions factors involved in cardiac development, which is comparable to the genes that cause PS in humans. However, validation studies and functional follow up is necessary before this information can be used for screening purposes.

Assessment of Carotid Intima Media Thickness and Left Ventricular Mass Index in Children with Idiopathic Nephrotic Syndrome

BACKGROUND

Children with nephrotic syndrome (NS) are at a greater risk of atherosclerosis due to recurrent exposures to hyperlipidemia, hypertension, and immunosuppressive medications. CIMT (carotid intima media thickness) is a reliable marker for assessment of atherosclerosis of large and medium-sized blood vessels; endothelial dysfunction and increased CIMT usually precede the development of cardiovascular diseases. Some manifestations of NS, like proteinuria and hyperlipidemia, are associated with an increased risk of cardiac morbidity and mortality. The aim of the current study was to evaluate the carotid intima media thickness and LVM (left ventricular mass) thickness in children with nephrotic syndrome.

SUBJECTS AND METHODS

Eighty-one children with nephrotic syndrome and 100 healthy children as controls were enrolled in the study. The inclusion criteria were: disease duration of minimum of 12 months, glomerular filtration rate >60mL/min/1.73m 2 and children aged two years or more at the time of study. CIMT and left ventricular mass index, lipid profile, protein/creatinine ratio in urine and kidney function tests were done for cases and controls after approval of internal ethical committee.

RESULTS

The mean CIMT (mm) was significantly higher in NS (0.51± 0.12) compared to controls (0.42± 0.09) (P <0.001). LVM and LVM Index were significantly higher in NS than controls (p< 0.001, for both). Subsequently, CIMT was significantly correlated to duration of the disease (p< 0.001), LVM index was significantly correlated with duration of the disease, body mass index (BMI), blood pressures and triglycerides level (p< 0.05).

CONCLUSION

Children with NS are at increasing risk to develop atherosclerosis as measured by CIMT. LVM was significantly higher in NS and positively correlated to BP, disease duration, triglyceride levels and BMI.

Genetic aspects of congenital nephrotic syndrome: a consensus statement from the ERKNet-ESPN inherited glomerulopathy working group

Congenital nephrotic syndrome (CNS) is a heterogeneous group of disorders presenting with massive proteinuria within the first 3 months of life almost inevitably leading to end-stage kidney disease. The Work Group for the European Reference Network for Kidney Diseases (ERKNet) and the European Society for Pediatric Nephrology (ESPN) has developed consensus statement on genetic aspects of CNS diagnosis and management. The presented expert opinion recommends genetic diagnostics as the key diagnostic test to be ordered already during the initial evaluation of the patient, discusses which phenotyping workup should be performed and presents known genotype-phenotype correlations.

Cardiovascular disease risk among children with focal segmental glomerulosclerosis: a report from the chronic kidney disease in children study

BACKGROUND

The aims were to compare the cardiovascular disease (CVD) risk among children with chronic kidney disease (CKD) secondary to focal segmental glomerulosclerosis (FSGS) with the CVD risk of children with CKD due to other diagnoses.

METHODS

Casual blood pressure (BP), ambulatory blood pressure monitoring (APBM), echocardiogram, lipids, carotid intima medial thickness (cIMT), and uric acid obtained from participants in the Chronic Kidney Disease in Children (CKiD) cohort were analyzed longitudinally. Seventy-nine children with FSGS (FSGS-CKD) were compared to 196 children with non-FSGS glomerular disease (GDO-CKD) and 616 children with non-glomerular disease (NG-CKD).

RESULTS

At baseline, FSGS-CKD (median 14 years) had ambulatory hypertension (24.6%), masked hypertension (46.2%), left ventricular hypertrophy (LVH) (26.3%), and dyslipidemia (60.0%). In adjusted models, FSGS-CKD had higher systolic BP z-score (0.52 vs 0.11 and 0.23, p = 0.002 and 0.02), triglycerides (133 vs 109 and 102 mg/dl, p = 0.007 and < 0.001), and non-high density lipoprotein (144 vs 132 and 119 mg/dl, p = 0.07 and < 0.001) at baseline when compared to GDO-CKD and NG-CKD, respectively. Left ventricular mass index (LVMI) (36.0 vs 31.7 g/m^2.7, p < 0.001) and the odds of LVH (OR 3.38, 95% CI 1.42, 8.08) at baseline were greater in FSGS-CKD compared to NG-CKD. Adjusted longitudinal analysis showed that FSGS-CKD had a faster decline in LVMI than NG-CKD, and FSGS-CKD had a faster increase in uric acid compared to both groups.

CONCLUSIONS

Children with CKD due to FSGS had a relatively high prevalence of CVD risk factors. FSGS was associated with greater CVD risk when compared to other CKD diagnoses.

Genetic abnormalities and prognosis in patients with congenital and infantile nephrotic syndrome

BACKGROUND

Congenital nephrotic syndrome (CNS) and infantile nephrotic syndrome (INS) are caused primarily by mutations in genes that encode structural and regulatory proteins of the glomerular filtration barrier. The aim of this study was to determine genotype-phenotype correlations and prognosis in patients with CNS and INS.

METHODS

NPHS1, NPHS2, LAMB2 and the eighth and ninth exons of WT1 were sequenced in 80 and 22 patients with CNS and INS, respectively. Genotype-phenotype correlations and survival were evaluated.

RESULTS

Causative mutations were identified in 64.7 % of patients, of which NPHS1 mutations were the most common (37.4 %). The mutation detection rate was twofold higher in CNS patients than in INS patients (72.5 vs. 36.2 %). The most commonly mutated gene in CNS patients was NPHS1 (46.3 %) versus NPHS2 (13.6 %) and WT1 (13.6 %) in INS patients. NPHS2 mutations, female patients with NPHS1 mutations, and NPHS1 mutations affecting the transmembrane or intracellular domains of nephrin were associated with longer survival.

CONCLUSIONS

Based on our present findings, the likelihood of identification of a genetic cause decreases with increasing age at diagnosis. The underlying genetic abnormality should be identified as early as possible, as this knowledge will facilitate clinicians in their prognostic prediction and enable patients to receive appropriate genetic counseling.

Subclinical cardiovascular disease and its association with risk factors in children with steroid-resistant nephrotic syndrome

BACKGROUND

The aim of this study was to evaluate the presence of subclinical cardiovascular disease (CVD) and its relation to risk factors in pediatric patients with steroid-resistant nephrotic syndrome (NS).

METHODS

Thirty-seven patients with normal renal function were compared with 22 healthy controls regarding the presence of subclinical CVD. Measurements included aortic pulse wave velocity (PWV), carotid intima media thickness (IMT), and left ventricular mass (LVM). Patients were additionally assessed for blood pressure (BP) pattern and the presence of hypertension by 24-h ambulatory blood pressure monitoring.

RESULTS

Compared with the controls, patients had significantly higher mean aortic PWV-standard deviation scores (SDS), mean carotid IMT-SDS, and LVM index (p < 0.001 for all). Increased aortic PWV was noted in 5 % of patients, increased carotid IMT in 22 %, and increased LVM index in 19 %. Five patients (14 %) were hypertensive, and mean BP indexes, SDS, and BP loads during nighttime were significantly higher than those during daytime (p < 0.001 for all). Multivariate analysis revealed a significant relationship between PWV-SDS and ferritin (R(2) = 0.269, p = 0.006) and between carotid IMT-SDS and proteinuria (R(2) = 0.141, p = 0.022). The LVM index was independently associated only with higher body mass index SDS (R(2) = 0.317, p < 0.001). In addition, six patients (16 %) had multiple abnormal subclinical CVD markers, and increased subclinical CVD risk was independently associated only with higher low-density lipoprotein cholesterol (R(2) = 0.292, p = 0.044).

CONCLUSIONS

Based on these results, steroid-resistant NS children generally are at high risk of cardiovascular complications, but the increased risk is likely to be multifactorial.

Cardiac findings in congenital nephrotic syndrome

INTRODUCTION

Congenital nephrotic syndrome is a severe debilitating problem associated with extra renal manifestation such as diverse cardiac findings.

METHODS

During four years, 6 cases diagnosed as congenital nephritic syndrome in base of definitive criteria their documents reviewed and echocardiographic evaluation has been done for all with or without cardiac sign or symptoms, results gathered and expressed as incidence.

RESULTS

All cases have some grades of structural or functional defects from simple form like as tricuspid regurgitation to complex defects. It may be run in consecutively in siblings of a family from non consanguine parents.

CONCLUSION

Pulmonary stenosis may occur in all parts subvalvualr, valvular and peripheral parts of pulmonary artery, left ventricular hypertrophy and mitral regurgitation observed in some, moderate tricuspid regurgitation observed in half of cases due to pulmonary hypertension or right ventricular hypertrophy due to pulmonary stenosis.

The podocyte protein nephrin is required for cardiac vessel formation

Nephrin (NPHS1) has been described as an important structural protein of kidney podocytes. Mutations in this gene lead to the Finnish-type congenital nephrotic syndrome. More recently, a role of nephrin as a signalling molecule in kidney podocytes has been identified. Here, we show that nephrin not only has a function in kidney podocytes, but is also required for cardiovascular development. Nephrin is expressed in the epicardium and coronary vessels during human and mouse embryonic development. Nephrin knockout embryos showed abnormal epicardial cell morphology and, at later stages of development, a reduced number of coronary vessels due to increased apoptosis, and in addition, cardiac fibrosis. Connexin 43, which is required for coronary vessel formation, was downregulated in nephrin knockout embryos. Expression of the p75NTR neurotrophin receptor, a known mediator of apoptosis, was increased in mutants. Furthermore, co-immunoprecipitation studies demonstrated a direct interaction of nephrin with p75NTR. Primary nephrin-deficient cardiac cells showed a 5-fold higher rate of apoptosis in response to progenitor of nerve growth factor compared with wild-type cells, which could be rescued by RNAi against p75NTR. Taken together, our data demonstrate that nephrin directly interacts with p75NTR and reveal an important role for nephrin in murine cardiac development by permitting survival of cardiovascular progenitor cells.

Eye involvement in children with primary focal segmental glomerulosclerosis

Distinct eye abnormalities have been described in children with nephrotic syndrome, particularly in diffuse mesangial sclerosis (i.e. Pierson syndrome). The aim of the study was to investigate whether there were any associated ocular anomalies in children with steroid-resistant nephrotic syndrome (SRNS), all of whom had revealed primary focal segmental glomerulosclerosis in biopsy. Thirty-three SRNS patients (16 male, 17 female) with a median age of 10.5 years (range 3-25 years) were enrolled in the study. Twenty steroid-sensitive nephrotic syndrome (SSNS) patients (ten male, ten female) with a median age of 8 years (range 3-15 years) served as controls. All SRNS patients were examined by mutational analysis for mutations in the NPHS2, WT1, and LAMB2 genes. Nine out of 33 SRNS patients (27.2%) showed various eye abnormalities. However, no abnormal ocular findings were detected in any of the SSNS patients. Abnormal eye findings detected in SRNS patients were anisometropic amblyopia (n = 4), Mittendorf's dots (n = 4), myopic astigmatism (n = 3) and exotropia (n = 1). Macular pigment changes (n = 1), posterior subcapsular opacities (n = 1) and cataract (n = 1) were considered as steroid-induced side effects. In four patients, more than one eye abnormality was found. Mutational analysis for the NPHS2, WT1 and LAMB2 genes revealed disease-causing mutations in 24.2% of patients. Homozygous NPHS2 mutations were detected in five patients (15.1%), all of whom had parental consanguinity. In three patients (9%) from non-consanguineous parents, heterozygous de novo WT1 mutations were detected as disease-causing mutations. No LAMB2 mutation was detected in any patient. While four out of five (80%) patients with homozygous NPHS2 mutations showed at least one abnormal ocular finding (i.e. Mittendorf's dot or anisometric amblyopia), none of the patients with a WT1 mutation had ocular involvement. In conclusion, ocular involvement may accompany SRNS caused by primary focal segmental glomerulosclerosis (FSGS). Ophthalmologic evaluation at the time of diagnosis might be beneficial to characterize further the spectrum of this possible association.

Recurrent nephrotic syndrome in homozygous truncating NPHS2 mutation is not due to anti-podocin antibodies

Mutations in NPHS2 are a common cause of focal segmental glomerulosclerosis (FSGS). It was initially assumed that FSGS caused by a genetically defective protein in the native kidney would not recur after transplantation; however, description of three patients with NPHS2 missense mutations challenged the validity of this assumption. A possible mechanism of recurrence in cases with stop-codon mutations is the formation of auto-antibodies against the truncated protein. In this case report, we describe a 9-year-old girl with the R138X NPHS2 mutation who presented with recurrent nephrotic syndrome 4 years after renal transplantation from a deceased donor, and was treated with plasmapheresis with a partial response. Renal histology did not demonstrate glomerular immunoglobulin deposition and an extensive search for anti-podocin antibodies based on indirect Western blot with recombinant podocin, was negative, as was the test for glomerular permeability factor (Palb). Taken together these findings confirm the possibility of post transplantation nephrotic syndrome in patients with NPHS2 mutations. Lack of immunoglobulin deposition, absence of circulating anti-podocin antibodies, and normal Palb suggest that other, unknown pathogenetic mechanisms are implicated.