Diagnostic Yield and Benefits of Whole Exome Sequencing in CAKUT Patients Diagnosed in the First Thousand Days of Life

Introduction

Congenital anomalies of the kidney and urinary tract (CAKUT) are the predominant cause of chronic kidney disease (CKD) and the need for kidney replacement therapy (KRT) in children. Although more than 60 genes are known to cause CAKUT if mutated, genetic etiology is detected, on average, in only 16% of unselected CAKUT cases, making genetic testing unproductive.

Methods

Whole exome sequencing (WES) was performed in 100 patients with CAKUT diagnosed in the first 1000 days of life with CKD stages 1 to 5D/T. Variants in 58 established CAKUT-associated genes were extracted, classified according to the American College of Medical Genetics and Genomics guidelines, and their translational value was assessed.

Results

In 25% of these mostly sporadic patients with CAKUT, a rare likely pathogenic or pathogenic variant was identified in 1 or 2 of 15 CAKUT-associated genes, including GATA3, HNF1B, LIFR, PAX2, SALL1, and TBC1D1. Of the 27 variants detected, 52% were loss-of-function and 18.5% de novo variants. The diagnostic yield was significantly higher in patients requiring KRT before 3 years of age (43%, odds ratio 2.95) and in patients with extrarenal features (41%, odds ratio 3.5) compared with patients lacking these criteria. Considering that all affected genes were previously associated with extrarenal complications, including treatable conditions, such as diabetes, hyperuricemia, hypomagnesemia, and hypoparathyroidism, the genetic diagnosis allowed preventive measures and/or early treatment in 25% of patients.

Conclusion

WES offers significant advantages for the diagnosis and management of patients with CAKUT diagnosed before 3 years of age, especially in patients who require KRT or have extrarenal anomalies.

Kidney biopsy diagnosis in childhood in the Norwegian Kidney Biopsy Registry and the long-term risk of kidney replacement therapy: a 25-year follow-up

BACKGROUND

There is scarce information on biopsy-verified kidney disease in childhood and its progression to chronic kidney disease stage 5 (CKD 5). This study aims to review biopsy findings in children, and to investigate risk of kidney replacement therapy (KRT).

METHODS

We conducted a retrospective long-term follow-up study of children included in the Norwegian Kidney Biopsy Registry (NKBR) and in the Norwegian Renal Registry (NRR) from 1988 to 2021.

RESULTS

In total, 575 children with a median (interquartile range, IQR) age of 10.7 (6.1 to 14.1) years were included, and median follow-up time (IQR) after kidney biopsy was 14.3 (range 8.9 to 21.6) years. The most common biopsy diagnoses were minimal change disease (MCD; n = 92), IgA vasculitis nephritis (IgAVN; n = 76), IgA nephropathy (n = 63), and focal and segmental glomerulosclerosis (FSGS; n = 47). In total, 118 (20.5%) of the biopsied children reached CKD 5, median (IQR) time to KRT 2.3 years (7 months to 8.4 years). Most frequently, nephronophthisis (NPHP; n = 16), FSGS (n = 30), IgA nephropathy (n = 9), and membranoproliferative glomerulonephritis (MPGN; n = 9) led to KRT.

CONCLUSIONS

The risk of KRT after a kidney biopsy diagnosis is highly dependent on the diagnosis. None of the children with MCD commenced KRT, while 63.8% with FSGS and 100% with NPHP reached KRT. Combining data from kidney biopsy registries with registries on KRT allows for detailed information concerning the risk for later CKD 5 after biopsy-verified kidney disease in childhood. A higher resolution version of the Graphical abstract is available as Supplementary information.

Rare heterozygous GDF6 variants in patients with renal anomalies

Although over 50 genes are known to cause renal malformation if mutated, the underlying genetic basis, most easily identified in syndromic cases, remains unsolved in most patients. In search of novel causative genes, whole-exome sequencing in a patient with renal, i.e., crossed fused renal ectopia, and extrarenal, i.e., skeletal, eye, and ear, malformations yielded a rare heterozygous variant in the GDF6 gene encoding growth differentiation factor 6, a member of the BMP family of ligands. Previously, GDF6 variants were reported to cause pleiotropic defects including skeletal, e.g., vertebral, carpal, tarsal fusions, and ocular, e.g., microphthalmia and coloboma, phenotypes. To assess the role of GDF6 in the pathogenesis of renal malformation, we performed targeted sequencing in 193 further patients identifying rare GDF6 variants in two cases with kidney hypodysplasia and extrarenal manifestations. During development, gdf6 was expressed in the pronephric tubule of Xenopus laevis, and Gdf6 expression was observed in the ureteric tree of the murine kidney by RNA in situ hybridization. CRISPR/Cas9-derived knockout of Gdf6 attenuated migration of murine IMCD3 cells, an effect rescued by expression of wild-type but not mutant GDF6, indicating affected variant function regarding a fundamental developmental process. Knockdown of gdf6 in Xenopus laevis resulted in impaired pronephros development. Altogether, we identified rare heterozygous GDF6 variants in 1.6% of all renal anomaly patients and 5.4% of renal anomaly patients additionally manifesting skeletal, ocular, or auricular abnormalities, adding renal hypodysplasia and fusion to the phenotype spectrum of GDF6 variant carriers and suggesting an involvement of GDF6 in nephrogenesis.

Lower urinary tract dysfunction in children - a practical approach

More than 10 % of schoolchildren suffer from lower urinary tract dysfunction, often leading to contact with the healthcare system. The problem is socially limiting as well as mentally and physically demanding for children and their parents, and it is important to offer treatment. This article describes a structured approach that can form the basis for correct diagnosis and treatment.

Skin conductance versus the modified COMFORT sedation score as a measure of discomfort in artificially ventilated children

OBJECTIVE

We wanted to use skin conductance as a measure of increased stress in artificially ventilated children. The aim was to examine how changes in skin conductance, arterial blood pressure, and heart rate are associated with changes in the modified COMFORT sedation score during suction from the trachea. Nociceptive stimulation induces an outgoing sympathetic nervous burst to the skin and the palmar and plantar sweat glands are filled, which creates a skin conductance fluctuation.

METHODS

Twenty children who were 1 day to 11 years of age were studied. All patients were artificially ventilated and circulatory stable. The data were obtained before, during, and 10 minutes after endotracheal suction. The number of skin conductance fluctuations, the amplitude of skin conductance fluctuations, the mean skin conductance level, arterial blood pressure, heart rate, and the modified COMFORT sedation score were recorded and tested from before to during and from during to after suction in the trachea. RESULTS. The number of skin conductance fluctuations, mean skin conductance level, arterial blood pressure, and the modified COMFORT sedation score increased during suction in the trachea, in contrast to heart rate and amplitude of skin conductance fluctuations. The number of skin conductance fluctuations from before to during and from during to after endotracheal suctioning correlated with changes in the modified COMFORT sedation score. This was in contrast to the other variables that did not.

CONCLUSIONS

The number of skin conductance fluctuations during endotracheal suctioning showed better correlation with the increase in the modified COMFORT sedation score than heart rate and arterial blood pressure. Thus, the number of skin conductance fluctuations seems to be an objective supplement to the modified COMFORT sedation score for monitoring increased stress in artificially ventilated and circulatory stable children.

Skin conductance or entropy for detection of non-noxious stimulation during different clinical levels of sedation

BACKGROUND

State entropy (SE) measures electroencephalographic signals, whereas response entropy (RE) also includes frontal electromyographic activity. In the presence of electromyographic activity, the RE index is larger than the SE index, the difference being denoted as RE-Delta (RE-Delta= RE - SE). Skin conductance (SC) may be expressed by a slow reacting variable, the mean SC level, the derivate of the mean SC level (D-SC), the number of SC fluctuations (NSCF) or the amplitude of the SC fluctuations (ASCF), which directly shows skin sympathetic nerve activity. The goal of this study was to evaluate whether these SC and entropy variables could differentiate between the responses obtained to load sound stimuli at different sedation levels before the induction of general anaesthesia.

METHODS

Twenty women scheduled for gynaecological laparotomy were studied. The modified observer's assessment of alertness sedation (OAAS) was used to classify the patients' hypnotic levels. White sounds (98 dB) were given at OAAS level 5 without propofol, at OAAS levels 4-3 and 3-2 with propofol and at OAAS levels 3-2 and < 2 with propofol and remifentanil.

RESULTS

RE and SE showed a steady decline from OAAS level 5 to level < 2 (P < 0.01). RE-Delta did not discriminate between any of the OAAS levels (P= NS). The mean SC level discriminated between OAAS levels 4-3 to < 2 (P < 0.01). D-SC discriminated between all the different OAAS levels (P < 0.01). NSCF discriminated between OAAS levels 5 to 3-2 (P < 0.05), but did not discriminate at OAAS level 3-2 between propofol alone or combined with remifentanil, or between OAAS level 3-2 and < 2. ASCF differentiated between OAAS levels 5 and 4 (P < 0.001) and OAAS levels 3-2 and < 2 (P < 0.05) only.

CONCLUSION

RE, SE and D-SC showed a similar discrimination between sound responses at the different sedation levels.

Comparison of skin conductance with entropy during intubation, tetanic stimulation and emergence from general anaesthesia

BACKGROUND

The number of skin conductance fluctuations (NSCF) expresses sympathetic skin nerve activity. The response entropy (RE) measures electromyographic and electroencephalographic activity in the forehead. The state entropy (SE) measures mainly electroencephalographic activity. When the suppression of frontal muscular activity is complete, RE is equal to SE. RE-Delta is defined as SE minus RE. The purposes of this study were to examine whether NSCF and RE-Delta correlate with signs of clinical stress during intubation and tetanic noxious stimulation and to elucidate how rapidly and accurately entropy and NSCF react during emergence from general anaesthesia.

METHODS

Twenty women scheduled for gynaecological laparotomy were studied. During intubation in remifentanil and propofol general anaesthesia, NSCF and RE-Delta were correlated with the clinical stress score. After a wash-out period, two series of tetanic stimuli were given, the first with (R+) and the second without (R-) remifentanil infusion. The tetanic pre-stimuli periods were compared with the tetanic post-stimuli periods, and R+ was compared with R-. During emergence, the responses of entropy and skin conductance were related to the time of extubation.

RESULTS

NSCF correlated well with the clinical stress score during intubation (r(2)= 0.73, P < 0.0005). RE-Delta showed a weaker correlation (r(2)= 0.33, P= 0.007). During tetanic stimuli, the NSCF pre-stimuli level was lower than the post-stimuli level (P < 0.001), and the NSCF R+ response was lower than the NSCF R- response (P= 0.002). RE-Delta did not show similar differences. During emergence, RE reacted before NSCF and SE (P= 0.003).

CONCLUSION

NSCF was better than RE-Delta for the measurement of clinical stress during intubation, and was sensitive to tetanic stimuli at different opioid analgesic levels, by contrast with RE-Delta. Both modalities were able to predict emergence at the end of anaesthesia, but RE was more rapid.