Cystic kidney diseases are a very heterogeneous group of chronic kidney diseases. The diagnosis is usually based on clinical and ultrasound characteristics and the final diagnosis is often difficult ...to be made. Next-generation sequencing (NGS) may help the clinicians to find the correct final diagnosis. The aim of our study was to test the diagnostic yield of NGS and its ability to improve the diagnosis precision in a heterogeneous group of children with cystic kidney diseases. Next-generation sequencing of genes responsible for the formation of cystic kidneys was performed in 31 unrelated patients with various clinically diagnosed cystic kidney diseases gathered at the Department of Pediatrics of Motol University Hospital in Prague between 2013 and 2018. The underlying pathogenic variants were detected in 71% of patients (n = 22), no or only one (in case of autosomal recessive inheritance) pathogenic variant was found in 29% of patients (n = 9). The result of NGS correlated with the clinical diagnosis made before the NGS in 55% of patients (n = 17), in the remaining 14 children (45%) the result of NGS revealed another type of cystic kidney disease that was suspected clinically before or did not find causal mutation in suspected genes. The most common unexpected findings were variants in nephronophthisis (NPHP) genes in children with clinically suspected autosomal recessive polycystic kidney disease (ARPKD, n = 4). Overall, 24 pathogenic or probably pathogenic variants were detected in the PKHD1 gene, 8 variants in the TMEM67 gene, 4 variants in the PKD1 gene, 2 variants in the HNF1B gene and 2 variants in BBS1 and NPHP1 genes, respectively. NGS is a valuable tool in the diagnostics of various forms of cystic kidney diseases. Its results changed the clinically based diagnoses in 16% (n = 5) of the children.
Mutations in INF2 are frequently responsible for focal segmental glomerulosclerosis (FSGS), which is a common cause of end stage renal disease (ESRD); additionally, they are also connected with ...Charcot-Marie-Tooth neuropathy. INF2 encodes for inverted formin 2. This protein participates in regulation of the dynamics of the actin cytoskeleton, involving not only the polymerisation, but also the depolymerisation of filaments. The present study is the first mutational analysis of INF2 done in the Czech Republic.
Mutational analysis of INF2 was performed on 109 patients (mean age at onset 41.44 ± 18.91 years) with FSGS or minimal change disease (MCD); and also in 6 patients without renal biopsy who had already developed chronic kidney disease (CKD)/ESRD at the time of diagnosis. We used high resolution melting method (HRM), with subsequent Sanger sequencing, in suspect samples from HRM analysis. The HRM method is an effective method for the screening of large cohorts of patients.
Two pathogenic mutations (p.Arg214His and p.Arg218Gln) were detected in INF2. The first (p.Arg214His) was identified in the FSGS patient with a positive family history. The second mutation (p.Arg218Gln) was found in two brothers with ESRD of unknown etiology. The most frequent sequence change was the substitution p.P35P, the incidence of which corresponded with the frequencies available in the ExAC Browser and gnomAD Browser databases. This analysis also detected different exonic and intronic changes that probably did not influence the phenotype of the included patients.
The INF2 mutational screening is useful in familial FSGS cases as well as in patients with an unknown cause for their ESRD, but with a positive family history. INF2 seems to be not only the cause of FSGS, but also of ESRD of unknown etiology. Our study has confirmed that the HRM analysis is a very useful method for the identification of single nucleotide substitutions.
Autosomal dominant polycystic kidney disease (ADPKD) is the most common genetic renal disease, with an estimated prevalence between 1:1000 and 1:2500. It is mostly caused by mutations of the
and
...genes encoding polycystin 1 (PC1) and polycystin 2 (PC2) that regulate cellular processes such as fluid transport, differentiation, proliferation, apoptosis and cell adhesion. Reduction of calcium ions and induction of cyclic adenosine monophosphate (sAMP) promote cyst enlargement by transepithelial fluid secretion and cell proliferation. Abnormal activation of MAPK/ERK pathway, dysregulated signaling of heterotrimeric G proteins, mTOR, phosphoinositide 3-kinase, AMPK, JAK/STAT activator of transcription and nuclear factor kB (NF-kB) are involved in cystogenesis. Another feature of cystic tissue is increased extracellular production and recruitment of inflammatory cells and abnormal connections among cells. Moreover, metabolic alterations in cystic cells including defective glucose metabolism, impaired beta-oxidation and abnormal mitochondrial activity were shown to be associated with cyst expansion. Although tolvaptan has been recently approved as a drug that slows ADPKD progression, some patients do not tolerate tolvaptan because of frequent aquaretic. The advances in the knowledge of multiple molecular pathways involved in cystogenesis led to the development of animal and cellular studies, followed by the development of several ongoing randomized controlled trials with promising drugs. Our review is aimed at pathophysiological mechanisms in cystogenesis in connection with the most promising drugs in animal and clinical studies.
Genetic focal segmental glomerulosclerosis (FSGS) is caused by pathogenic variants in a broad spectrum of genes that have a variable representation based on subjects' ethnicity and/or age. The most ...frequently mutated autosomal recessive gene in FSGS is
. In this study, we analyzed the spectrum of
variants and their associated phenotype in Czech adult FSGS patients.
A representative cohort of 234 adult patients with FSGS, derived from 225 families originating from all regions of Czechia, was analyzed by massively parallel sequencing. In this study, we focused on the comprehensive analysis of the
gene. The histological classification of FSGS followed the Columbia classification.
We detected seven (3%) cases bearing homozygous or compound heterozygous pathogenic
variants. A single pathogenic variant c.868G > A (p.Val290Met) was found in the majority of
-positive cases (86%; 6 out of 7) in histologically confirmed instances of FSGS. Its allele frequency among unrelated
-associated FSGS patients was 50% (6/12), and Haplotype analysis predicted its origin to be a result of a founder effect. There is an identical V290M-related haplotype on all V290M alleles spanning a 0,7 Mb region flanking
in Central European FSGS populations. The phenotype of the p.Val290Met
-associated FSGS demonstrated a later onset and a much milder course of the disease compared to other
pathogenic variants associated with FSGS. The mean age of the FSGS diagnosis based on kidney biopsy evaluation was 31.2 ± 7.46 years. In 50% of all cases, the initial disease manifestation of proteinuria occurred only in adulthood, with 83% of these cases not presenting with edemas. One-third (33%) of the studied subjects progressed to ESRD (2 out of 6) at the mean age of 35.0 ± 2.82 years.
We identified the most prevalent pathogenic variant, p.Val290Met, in the
gene among Czech adult FSGS patients, which has arisen due to a founder effect in Central Europe. The documented milder course of the disease associated with this variant leads to the underdiagnosis in childhood. We established the histopathological features of the
-associated adult FSGS cases based on the Columbia classification. This might improve patient stratification and optimize their treatment.
Alport syndrome (AS) is a hereditary kidney disease caused by pathogenic variants in
and
genes with autosomal recessive or autosomal dominant transmission or in the
gene with X-linked inheritance. ...Digenic inheritance was also described. Clinically it is associated with microscopic hematuria, followed by proteinuria and chronic renal insufficiency with end-stage renal disease in young adults. Nowadays, there is no curative treatment available. The inhibitors of RAS (renin-angiotensin system) since childhood slow the progression of the disease. Sodium-glucose cotransporter-2 inhibitors seem to be promising drugs from DAPA-CKD (dapagliflozin-chronic kidney disease) study, but only a limited number of patients with Alport syndrome was included. Endothelin type A receptor and angiotensin II type 1 receptor combined inhibitors, and lipid-lowering agents are used in ongoing studies in patients with AS and focal segmental glomerulosclerosis (FSGS). Hydroxychloroquine in AS is studied in a clinical trial in China. Molecular genetic diagnosis of AS is crucial not only for prognosis prediction but also for future therapeutic options. Different types of mutations will require various types of gene, RNA, or protein therapy to improve the function, the of final protein product.
Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary renal disorder, leading to end stage renal failure and kidney transplantation in its most serious form. The severity ...of the disease's manifestation depends on the genetic determination of ADPKD. The huge variability of different phenotypes (even within a single family) is not only modulated by the two main ADPKD genes (PKD1 and PKD2) but also by modifier genes and the whole genetic background.
This is a report of an ADPKD family with co-inheritance of PKD1 and PKD2 pathogenic variants. The proband, with an extremely serious manifestation of ADPKD (the man was diagnosed in early childhood, and with end stage renal disease aged 23), underwent genetic analysis of PKD1 and PKD2, which revealed the presence of pathogenic mutations in both of these genes. The missense PKD2 mutation p.Arg420Gly came from the proband's father, with a mild ADPKD phenotype. The same mutation of the PKD2 gene and similar mild disease presentation were found in the proband's aunt (father's sister) and her son. The nonsense mutation p.Gln2196* within the PKD1 gene was probably inherited from the proband's mother, who died at the age of 45. It was only discovered post mortem, that the real cause of her death was kidney failure as a consequence of untreated ADPKD. Unfortunately, neither the DNA of the proband's mother nor the DNA of any other family members from this side of the pedigree were available for further examination. The proband underwent successful cadaveric kidney transplantation at the age of 24, and this replacement therapy lasted for the next 15 years.
Here, we present a first case of bilineal ADPKD inheritance in the Czech Republic. This report highlights the significant role of modifier genes in genetic determination of ADPKD, especially in connection with seriously deteriorated disease phenotypes. In our case, the modifying role is probably mediated by the PKD2 gene.
IgA nephropathy (IgAN) is the most common glomerulonephritis, which may also coexist with other diseases. We present two patients with an unusual coincidence of IgAN and Fabry disease (FD).
A 26 ...year-old man underwent a renal biopsy in February 2001. Histopathology showed very advanced IgAN and vascular changes as a result of hypertension. Because of his progressive renal insufficiency the patient began hemodialysis in August 2001. By means of the blood spot test screening method the diagnosis of FD was suspected. Low activity of alpha-galactosidase A in the patient's plasma and leukocytes and DNA analysis confirmed the diagnosis of FD. Enzyme replacement therapy started in July 2004. Then the patient underwent kidney transplantation in November 2005. Currently, his actual serum creatinine level is 250 μmol/l. Other organ damages included hypertrophic cardiomyopathy, neuropathic pain and febrile crisis. After enzyme replacement therapy, myocardial hypertrophy has stabilized and other symptoms have disappeared. No further progression of the disease has been noted.The other patient, a 30 year-old woman, suffered from long-term hematuria with a good renal function. Recently, proteinuria (2.6 g/day) appeared and a renal biopsy was performed. Histopathology showed IgAN with remarkably enlarged podocytes. A combination of IgAN and a high suspicion of FD was diagnosed. Electron microscopy revealed dense deposits in paramesangial areas typical for IgAN and podocytes with inclusive zebra bodies and myelin figures characteristic of FD. FD was confirmed by the decreased alpha-galactosidase A activity in plasma and leukocytes and by DNA and RNA analysis. Enzyme replacement therapy and family screening were initiated.
Our results emphasize the role of complexity in the process of diagnostic evaluation of kidney biopsy samples. Electron microscopy represents an integral part of histopathology, and genetic analysis plays a more and more important role in the final diagnosis, which is followed by causal treatment.
Background/Aims: The aim of our study was to retrospectively analyse data of 520 Czech patients with IgA nephropathy (IgAN) and to specify the risk factors affecting renal survival of IgAN patients. ...Methods: Cox proportional hazards regression model was used to evaluate the effects of different variables on renal survival during a median follow up of six years. McNemar´s test was used to analyse the progression of renal function according to Bartosik´s formula. Results: In our retrospective analysis of 520 Czech IgAN patients Cox proportional hazards regression model with five variables hypertension, sex, GFR, proteinuria, age was used. Significant regression coefficient was found for GFR, hypertension and proteinuria. Using stepwise algorithm GFR (OR = 3.09), hypertension (OR = 2.09) and proteinuria (OR = 1.97) were found as the most important factors for renal survival in our group of IgAN patients. Among patients with CKD 3 we found significantly better renal survival in patients with proteinuria < 1g/day compared to patients with higher proteinuria. We did not find the significant difference between predicted progression of renal function due to Bartosik´s formula and real progression of renal parametres assessed by GFR at the end of the follow up in our group of IgAN patients. Conclusion: Our retrospective study of 520 Czech IgAN patients confirmed GFR, hypertension and proteinuria as the most important factors affecting the prognosis of IgAN patients. We validated Toronto Bartosik´s formula to predict prognosis of IgAN patients.
Background & Aims
Polycystic liver disease (PLD) occurs in two genetic disorders, autosomal‐dominant polycystic kidney disease (ADPKD) and autosomal‐dominant polycystic liver disease (ADPLD). The aim ...of this study is to compare disease severity between ADPKD and ADPLD by determining the association between diagnosis and height‐adjusted total liver volume (hTLV).
Methods
We performed a cross‐sectional analysis with hTLV as endpoint. Patients were identified from the International PLD Registry (>10 liver cysts) and included in our analysis when PLD diagnosis was made prior to September 2017, hTLV was available before volume‐reducing therapy (measured on computed tomography or magnetic resonance imaging) and when patients were tertiary referred. Data from the registry were retrieved for age, diagnosis (ADPKD or ADPLD), gender, height and hTLV.
Results
A total of 360 patients (ADPKD n = 241; ADPLD n = 119) met our inclusion criteria. Female ADPKD patients had larger hTLV compared with ADPLD (P = 0.008). In a multivariate regression analysis, ADPKD and lower age at index CT were independently associated with larger hTLV in females, whereas in males a higher age was associated with larger hTLV. Young females (≤51 years) had larger liver volumes compared with older females (>51 years) in ADPKD.
Conclusion
Aetiology is presented as a new risk factor associated with PLD severity. Young females with ADPKD represent a subgroup of PLD patients with the most severe phenotype expressed in hTLV.
Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary renal disease. The disease is caused by mutations of the PKD1 (affecting roughly 85% of ADPKD patients) and PKD2 ...(affecting roughly 14% of ADPKD patients) genes, although in several ADPKD families, the PKD1 and/or PKD2 linkage was not found. Mutation analysis of the PKD1 gene is complicated by the presence of highly homologous genomic duplications of the first two thirds of the gene.
The direct detection of mutations in the non-duplicated region of the PKD1 gene was performed in 90 unrelated individuals, consisting of 58 patients with end-stage renal failure (manifesting before their 50th year of life) and 32 individuals from families where the disease was clearly linked to the PKD1 gene. Mutation screening was performed using denaturing gradient gel electrophoresis (DGGE). DNA fragments showing an aberrant electrophoretic banding pattern were sequenced.
In the non-duplicated region of the PKD1 gene, 19 different likely pathogenic germline sequence changes were identified in 19 unrelated families/individuals. Fifteen likely pathogenic sequence changes are unique for the Czech population. The following probable mutations were identified: 9 nonsense mutations, 6 likely pathogenic missense mutations, 2 frameshifting mutations, one in-frame deletion and probable splice site mutation. In the non-duplicated region of the PKD1 gene, 16 different polymorphisms or unclassified variants were detected.
Twenty probable mutations of the PKD1 gene in 90 Czech individuals (fifteen new probable mutations) were detected. The establishment of localization and the type of causal mutations and their genotype phenotype correlation in ADPKD families will improve DNA diagnosis and could help in the assessment of the clinical prognosis of ADPKD patients.
PDF
