Anna Moczulska

Genotype-phenotype associations in WT1 glomerulopathy.

WT1 mutations cause a wide spectrum of renal and extrarenal manifestations. Here we evaluated disease prevalence, phenotype spectrum, and genotype-phenotype correlations of 61 patients with WT1-related steroid-resistant nephrotic syndrome relative to 700 WT1-negative patients, all with steroid-resistant nephrotic syndrome. WT1 patients more frequently presented with chronic kidney disease and hypertension at diagnosis and exhibited more rapid disease progression. Focal segmental glomerulosclerosis was equally prevalent in both cohorts, but diffuse mesangial sclerosis was largely specific for WT1 disease and was present in 34% of cases. Sex reversal and/or urogenital abnormalities (52%), Wilms tumor (38%), and gonadoblastoma (5%) were almost exclusive to WT1 disease. Missense substitutions affecting DNA-binding residues were associated with diffuse mesangial sclerosis (74%), early steroid-resistant nephrotic syndrome onset, and rapid progression to ESRD. Truncating mutations conferred the highest Wilms tumor risk (78%) but typically late-onset steroid-resistant nephrotic syndrome. Intronic (KTS) mutations were most likely to present as isolated steroid-resistant nephrotic syndrome (37%) with a median onset at an age of 4.5 years, focal segmental glomerulosclerosis on biopsy, and slow progression (median ESRD age 13.6 years). Thus, there is a wide range of expressivity, solid genotype-phenotype associations, and a high risk and significance of extrarenal complications in WT1-associated nephropathy. We suggest that all children with steroid-resistant nephrotic syndrome undergo WT1 gene screening.

Clinical InvestigationGenotype–phenotype associations in WT1 glomerulopathy

WT1 mutations cause a wide spectrum of renal and extrarenal manifestations. Here we evaluated disease prevalence, phenotype spectrum, and genotype-phenotype correlations of 61 patients with WT1-related steroid-resistant nephrotic syndrome relative to 700 WT1-negative patients, all with steroid-resistant nephrotic syndrome. WT1 patients more frequently presented with chronic kidney disease and hypertension at diagnosis and exhibited more rapid disease progression. Focal segmental glomerulosclerosis was equally prevalent in both cohorts, but diffuse mesangial sclerosis was largely specific for WT1 disease and was present in 34% of cases. Sex reversal and/or urogenital abnormalities (52%), Wilms tumor (38%), and gonadoblastoma (5%) were almost exclusive to WT1 disease. Missense substitutions affecting DNA-binding residues were associated with diffuse mesangial sclerosis (74%), early steroid-resistant nephrotic syndrome onset, and rapid progression to ESRD. Truncating mutations conferred the highest Wilms tumor risk (78%) but typically late-onset steroid-resistant nephrotic syndrome. Intronic (KTS) mutations were most likely to present as isolated steroid-resistant nephrotic syndrome (37%) with a median onset at an age of 4.5 years, focal segmental glomerulosclerosis on biopsy, and slow progression (median ESRD age 13.6 years). Thus, there is a wide range of expressivity, solid genotype-phenotype associations, and a high risk and significance of extrarenal complications in WT1-associated nephropathy. We suggest that all children with steroid-resistant nephrotic syndrome undergo WT1 gene screening.

Retrospective cohort study of familial hypomagnesaemia with hypercalciuria and nephrocalcinosis due to CLDN16 mutations

BACKGROUND Familial hypomagnesaemia with hypercalciuria and nephrocalcinosis (FHHNC) is a rare autosomal recessive tubular disorder exhibiting a high risk for progressive chronic kidney disease (CKD). METHODS This is a retrospective multicentre study of 25 paediatric cases with FHHNC in Poland. Median age at diagnosis was 4 years and median follow-up time was 4.8 years. RESULTS All cases of FHHNC carried recessive mutations in CLDN16. The founder mutation in CLDN16, Leu151Phe, was the most frequent cause of FHHNC in Polish patients, with 13 (52%) cases being homozygous and 5 (20%) carrying Leu151Phe allele in compound heterozygosity. All cases showed nephrocalcinosis, increased urinary fractional excretion of magnesium and hypercalciuria. Other disease features included hypomagnesaemia (76%), hyperparathyroidism (76%), hyperuricaemia (56%) and hypocitraturia (60%). Treatment with thiazides effectively reduced hypercalciuria in most cases. During follow-up, renal function declined in 60% of patients; 12% of patients reached CKD stage 3 or 4 and one patient developed end-stage renal failure. CONCLUSIONS We report one of the largest cohorts of FHHNC cases caused by CLDN16 mutations. A missense variant of CLDN16, Leu151Phe, is the most common mutation responsible for FHHNC in Poland. Additionally, we found that normomagnesaemia does not exclude FHHNC and the calculation of fractional excretion of Mg can be diagnostic in the setting of normomagnesaemia. We also demonstrate the efficacy of a treatment with thiazides in terms of hypercalciuria in the majority of patients.

Which equations should and which should not be employed in calculating eGFR in children

PURPOSE We assessed the reliability of calculating eGFR in children as compared to the iohexol disappearance test (GFR-I), which was performed 417 times in 353 children aged 2 and more. MATERIAL/METHODS eGFR was estimated with equations based on serum creatinine: Schwartz (1: eGFR-Scr), Cockroft-Gault (2: eGFR-CG) and MDRD (3: eGFR-MDRD), and on creatinine clearance (4: eGFR-U), or relying on serum cystatin C: Hoeck (5: eGFR-H), Bokenkamp (6: eGFR-B) and Filler (7: eGFR-F), and on the three Schwartz markers (8: eGFR-S3M). Mean relative error (RE), correlation (R), Bland-Altman analysis and accuracy of GFR-I were studied in all patients and in subgroups: at GFR<60ml/min/1.73m(2); in children aged ≤12 and >12. RESULTS The results by eGFR-Scr, eGFR-S3M demonstrated no statistical difference to GFR-I at GFR<60ml/min/1.73m(2), but underestimated eGFR at higher filtration values by 11.6±15.1% and 19.1±16.4, respectively (p<0.0000). The eGFR-B, eGFR-F and eGFR-MDRD equations illustrated important overestimation of reference GFR results (RE: 84±44.2%; 29.5±27.9%, 35.6±62%; p<0.0000 for all). The MDRD and C-G formulas showed statistically better consistency in children aged >12. A good agreement was achieved by the eGFR-H equation (5.1±21.9%; p<0.0000; R=0.78). CONCLUSIONS (1) Schwartz equations show a good conformity at GFR<60ml/min/1.73m(2), but underestimate the results at higher GFR values. (2) The Bokenkamp equation with original coefficient should not be employed in children. (3) The use of the Hoeck formula in all children and C-G and MDRD formula in children aged >12 is possible. (4) The error of eGFR calculations increases at higher GFR values.

Modification of the Schwartz equations for children increases their accuracy at eGFR > 60 mL/min/1.73 m2

Abstract Aim: Estimation of eGFR in children with normal kidney function using the Schwartz equations results in underestimating real GFR. Materials and methods: We propose modification of three Schwartz equations – two based on creatinine concentration (eGFRScrBS bedside) and (eGFRScr) and one 3-marker based on creatinine, urea and cystatin C concentrations (eGFRS3M). The iohexol test (reference method) was performed 417 times in 353 children >2 years with mean GFR: 98 ± 31.6 ml/min/1.73m2. The assessment included also the Filler and Zappitelli equations. The modification was performed using methods: (1) based on equation, eGFRcor = a [eGFR − T] + T, where T = 50, if eGFR > T, and a equals for: eGFRScrBS 1.4043, for eGFRScr 2.0048, for eGFRS3M 1.2951, and (2) based on correction of all coefficients of the original equation. Results: For comparison of all the results and for children with GFR< 60, 60-90, 90-135 and > 135 ml/min/1.73m2 the correlation coefficient, relative error (RE) and root mean square relative error (RMSRE) was employed and revealed improvement of RE from 25.9 to 6.8 and 3.9% (depending on the correction method) for eGFRScr; from 19 to 8.1 and 3.9% for eGFRScrBS and: from 11.6% to 2.0 and 2.3% for eGFRS3M (respectively). The RMSRE values changed from 30 to 21.3 and 19.8% for eGFRScr, from 25.1 to 21.6 and 19.8% for eGFRScrBS and from 19.1 to 15.8 and 15.3 % for eGFRS3M. Conclusions: Modifications of Schwartz equations at GFR > 60 ml/min/1.73m2 significantly improves the accuracy of calculating eGFR. The 3-markers equation is more accurate and should be employed frequently.

Multicenter analysis of the efficacy and safety of a non-standard immunosuppressive therapy with rituximab in children with steroid-resistant nephrotic syndrome

The aim of the study was a multicenter analysis of the efficacy and safety of a non‐standard immunosuppressive therapy with rituximab (Rtx) in children with steroid‐resistant nephrotic syndrome (SRNS) with particular emphasis on the possibility of permanent discontinuation or dose reduction of other immunosuppressive drugs such as glucocorticoids and cyclosporine A after 6 months of observation. The study group consisted of 30 children with idiopathic nephrotic syndrome, who were unresponsive to standard immunosuppressive treatment, and hospitalized in the years 2010–2017 in eight paediatric nephrology centres in Poland. The children were administered a single initial infusion of rituximab at the dose of 375 mg/m2 of the body surface area. Proteinuria, the daily supply of glucocorticoids, and cyclosporine were assessed at the moment of the start of the treatment and after 6 months since its commencement. Before Rtx therapy, complete remission was found in 13 patients (43%) and partial remission was found in 8 patients (26%). These numbers increased to 16 (53%) and 12 (40%), respectively. At the start of the treatment 23 patients (76.6%) were treated with cyclosporine A. After 6 months, this number decreased to 15 patients (35%). At the start of the treatment, 18 patients (60%) were treated with prednisone. After 6 months, this number decreased to 8 patients (44%). Children with SRNS may potentially benefit from Rtx treatment despite relative risk of side effects. The benefits may include reduction of proteinuria or reduction of other immunosuppressants.

Assessment of growth retardation in children on renal replacement therapy from 2000 to 2016 – one center experience

W S TĘP: Celem pracy była ocena wzrastania dzieci dializowanych w latach 2000–2016. M A T E R I AŁ I M E T O D A: U 102 dzieci w wieku 10,2 roku ± 5,66 przeanalizowano rozpoznania, schorzenia dodatkowe, czas i rodzaj dializoterapii, losy pacjenta, zastosowanie hormonu wzrostu. Niedobór wzrastania (Z score) stwierdzono u 87 dzieci przy rozpoczęciu badania i u 94 przy zakończeniu leczenia. W Y N I K I: U 60% dzieci pierwszą metodą dializoterapii była dializa otrzewnowa, u 38% hemodializoterapia, u 2% wyprzedzające przeszczepienie nerki. W chwili zakończenia obserwacji 70% pacjentów żyło z czynnym przeszczepem nerki, 15% było nadal dializowanych, 13% zmarło, u 2% doszło do poprawy funkcji nerek. Średni czas dializoterapii (94 dzieci) wynosił 34,6 mies. (1–136 mies.) i był dłuższy w latach 2000–2008 niż w okresie 2009–2016 (śr. 43,3 ± 32,7 mies. vs 18,3 ± 13,1; p = 0,00005). W grupie ze schorzeniami dodatkowymi (46% dzieci) stwierdzono większy niedobór wzrostu na początku (Z score 0: -2,3 ± 2,3 vs -1,08 ± 1,6; p = 0,003) i na końcu leczenia (Z score 1:-2,7 ± 2,6 vs -1,2 ± 1,5; p = 0,001) oraz dłuższy czas dializoterapii (42,7 ± 34,4 mies. vs 27,8 ± 23,8; p = 0,02). Z score 0 wyniósł dla wszystkich pacjentów -1,7 ± 2,0 (-9,3 do +2,0) przy rozpoczęciu leczenia i nie różnił się od Z score 1: -1,9 ± 2,2 (-8,3 do +2,4); p = 0,37 w chwili zakończenia. U 42,5% dzieci na początku i u 45% na końcu terapii Z score był < -2,0. W grupie 17% dzieci leczonych hormonem wzrostu stwierdzono wyrównanie się niedoboru wzrostu po zakończeniu dializoterapii w porównaniu z grupą nieleczoną (Z score 1: -2,4 ± 1,7 vs -1,9 ± 2,3; p = 0,37). W N I O S K I: Niskorosłość stanowi istotny problem dzieci dializowanych. Współchorobowość jest czynnikiem pogarszającym niedobór wzrostu. Zastosowanie hormonu wzrostu daje szansę na poprawę wzrastania.