Clinical Significance of the Cystic Phenotype in Alport Syndrome.

RATIONALE & OBJECTIVE: Alport syndrome (AS) is the most common genetic glomerular disease caused by mutations that affect type IV collagen. However, the clinical characteristics and significance of AS with kidney cysts are not well defined. This study investigated the prevalence and clinical significance of cystic kidney phenotype in AS. STUDY DESIGN: Retrospective cohort study. SETTING & PARTICIPANTS: One hundred-eight patients with AS and a comparison cohort of 79 patients with IgA nephropathy (IgAN). Clinical, genetic, and imaging data were collected from medical records. EXPOSURE: Cystic kidney phenotype evaluated by ultrasonography and defined as the presence of≥3 cysts in each kidney; demographic characteristics and estimated glomerular filtration rate (eGFR) at disease onset. OUTCOME: Cystic kidney phenotype in the AS and IgAN cohorts; time to chronic kidney disease (CKD) stage 3b and longitudinal changes in eGFR in the AS cohort. ANALYTICAL APPROACH: Logistic regression analysis to test independent strengths of associations of clinical/demographic features with the binary outcome of cystic phenotype. Survival analysis for the outcome of reaching CKD stage 3b and linear mixed models for changes in eGFR over time in the AS cohort. RESULTS: We studied 108 patients with AS; 76 (70%) had a genetic diagnosis. Autosomal dominant AS was prevalent, accounting for 68% of patients with a genetic diagnosis. Cystic kidney phenotype was observed in 38% of patients with AS and was associated with normal-sized kidneys in all but 3 patients, who showed increased total kidney volume, mimicking autosomal dominant polycystic kidney disease. The prevalence of cystic kidney phenotype was significantly higher in patients with AS when compared with the group of patients with IgAN (42% vs 19%; P=0.002). Patients with the cystic kidney phenotype were older and had more marked reduction in eGFR than patients without cystic changes. Among patients with AS, the cystic phenotype was associated with older age and a faster decline eGFR. LIMITATIONS: Retrospective, single-center study. CONCLUSIONS: Cystic kidney phenotype is a common finding in AS. The cystic kidney phenotype is a common finding in AS, suggesting a possible role in cystogenesis for the genetic variants that cause this disease. PLAIN-LANGUAGE SUMMARY: Hematuria is the classic renal presentation of Alport syndrome (AS), a hereditary glomerulopathy caused by pathogenic variants of the COL4A3-5 genes. An atypical kidney cystic phenotype has been rarely reported in individuals with these variants. To determine the prevalence of kidney cysts, we performed abdominal ultrasonography in a large group of patients with AS and a comparison group of patients with another glomerular kidney disease, IgA nephropathy (IgAN). Multiple kidney cysts, usually with normal kidney volume, were found in 38% of patients with AS. A few patients' kidney volumes were large enough to mimic a different hereditary cystic kidney disease, autosomal dominant polycystic kidney disease. The overall prevalence of kidney cysts in AS was more than double that observed in the well-matched comparison group with IgAN. These findings emphasize the high prevalence of cystic kidney phenotype in AS, suggesting a likely association between the genetic variants that cause this disease and the development of kidney cysts.

Monoallelic pathogenic IFT140 variants are a common cause of autosomal dominant polycystic kidney disease-spectrum phenotype.

Background: Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disorder, characterized by development and enlargement of kidney cysts, eventually leading to end-stage kidney disease (ESKD). Pathogenic variants in the PKD1 and PKD2 genes are the major cause of ADPKD; additional rare variants in the GANAB, DNAJB11, ALG5 and ALG9 genes have been found in a minority of ADPKD patients. More recently, a significant number of ADPKD families have been linked to monoallelic variants in the IFT140 gene. Methods: In this retrospective study, we tested the prevalence of the known causative genes of ADPKD-spectrum phenotype, including the PKD1, PKD2, GANAB, DNAJB11, ALG5, ALG and IFT140 genes, in a cohort of 129 ADPKD patients who consecutively underwent genetic testing in a single centre in Italy. Genetic testing utilized a combination of targeted next-generation sequencing, long-range polymerase chain reaction, Sanger sequencing and multiplex ligation-dependent probe amplification. Clinical evaluation was conducted through renal function testing and imaging features, including ultrasonography, computer tomography and magnetic resonance imaging. Results: Of the 129 enrolled patients, 86 (66.7%) had pathogenic variants in PKD1 and 28 (21.7%) in PKD2, loss of function pathogenic variants in the IFT140 gene were found in 3 unrelated patients (2.3%), no pathogenic variants were found in other ADPKD genes and 12 patients (9.3%) remained genetically unresolved (ADPKD-GUR). Familial clinical and genetic screening of the index patients with ADPKD due to an IFT140 pathogenic variant (ADPKD-IFT140) allowed identification of eight additional affected relatives. In the 11 ADPKD-IFT140 patients, the renal phenotype was characterized by mild and late-onset PKD, with large renal cysts and limited kidney insufficiency. Extrarenal manifestations, including liver cysts, were rarely seen. Conclusion: Our data suggest the monoallelic pathogenic IFT140 variants are the third most common cause of the ADPKD-spectrum phenotype in Italy, usually associated with a mild and atypical renal cystic disease.

Rare Single Nucleotide and Copy Number Variants and the Etiology of Congenital Obstructive Uropathy: Implications for Genetic Diagnosis.

SIGNIFICANCE STATEMENT: Congenital obstructive uropathy (COU) is a prevalent human developmental defect with highly heterogeneous clinical presentations and outcomes. Genetics may refine diagnosis, prognosis, and treatment, but the genomic architecture of COU is largely unknown. Comprehensive genomic screening study of 733 cases with three distinct COU subphenotypes revealed disease etiology in 10.0% of them. We detected no significant differences in the overall diagnostic yield among COU subphenotypes, with characteristic variable expressivity of several mutant genes. Our findings therefore may legitimize a genetic first diagnostic approach for COU, especially when burdening clinical and imaging characterization is not complete or available. BACKGROUND: Congenital obstructive uropathy (COU) is a common cause of developmental defects of the urinary tract, with heterogeneous clinical presentation and outcome. Genetic analysis has the potential to elucidate the underlying diagnosis and help risk stratification. METHODS: We performed a comprehensive genomic screen of 733 independent COU cases, which consisted of individuals with ureteropelvic junction obstruction ( n =321), ureterovesical junction obstruction/congenital megaureter ( n =178), and COU not otherwise specified (COU-NOS; n =234). RESULTS: We identified pathogenic single nucleotide variants (SNVs) in 53 (7.2%) cases and genomic disorders (GDs) in 23 (3.1%) cases. We detected no significant differences in the overall diagnostic yield between COU sub-phenotypes, and pathogenic SNVs in several genes were associated to any of the three categories. Hence, although COU may appear phenotypically heterogeneous, COU phenotypes are likely to share common molecular bases. On the other hand, mutations in TNXB were more often identified in COU-NOS cases, demonstrating the diagnostic challenge in discriminating COU from hydronephrosis secondary to vesicoureteral reflux, particularly when diagnostic imaging is incomplete. Pathogenic SNVs in only six genes were found in more than one individual, supporting high genetic heterogeneity. Finally, convergence between data on SNVs and GDs suggest MYH11 as a dosage-sensitive gene possibly correlating with severity of COU. CONCLUSIONS: We established a genomic diagnosis in 10.0% of COU individuals. The findings underscore the urgent need to identify novel genetic susceptibility factors to COU to better define the natural history of the remaining 90% of cases without a molecular diagnosis.

Expanding the variability of the ADPKD-GANAB clinical phenotype in a family of Italian ancestry.

BACKGROUND: Causative mutations in the GANAB gene have been described in only 14 families, 9 diagnosed with late-onset Autosomal Dominant Polycystic Kidney Disease (ADPKD) and 5 with Autosomal Dominant Polycystic Liver Disease (ADPLD). CASE: Diagnosis of ADPKD was made in a 45-year old man during screening for hernia repair. CT scan showed enlarged cystic kidneys, nephrolithiasis and normal-sized liver with multiple cysts. Hematuria, hypertension and aortic root dilatation were also documented. Renal function was normal. Molecular analysis of PKD genes disclosed a heterozygous p.R839W GANAB variant inherited from the mother. Both his elderly parents presented normal-sized bilateral cystic kidneys but normal renal function. The GANAB-ADPKD mother had no liver cysts. The father was screened for PKD-related genes and no variant was found. GENETIC ANALYSIS: We describe a new family with late-onset ADPKD due to the p.R839W GANAB variant, previously reported in a severe ADPLD patient, requiring liver transplantation. DISCUSSION: Since ADPKD-GANAB is an ultrarare, recently described disease, reporting further patients may help unraveling gene-related phenotype. In our patients the p.R839W GANAB variant was not related to severe ADPLD, as previously reported, but with mild ADPKD and a plethora of renal and extrarenal manifestations, usually described in PKD1/PKD2 patients. The evidence that the GANAB variant may cause both ADPKD and ADPLD of variable severity supports that renal and hepatic cystogenesis are the result of a common defective polycystin-1 pathway.

Variable Expressivity of HNF1B Nephropathy, From Renal Cysts and Diabetes to Medullary Sponge Kidney Through Tubulo-interstitial Kidney Disease.

INTRODUCTION: In humans, heterozygous mutations of hepatocyte nuclear factor 1beta (HNF1B) are responsible for a dominant inherited disease with both renal and extrarenal phenotypes. HNF1B nephropathy is the umbrella term that includes the various kidney phenotypes of the disease, ranging from congenital anomalies of the kidney and urinary tract (CAKUT), to tubular transport abnormalities, to chronic tubulointerstitial and cystic renal disease. METHODS: We describe 7 families containing 13 patients with ascertained HNF1B nephropathy. All patients underwent genetic testing and clinical, laboratory, and instrumental assessment, including renal imaging and evaluation of extrarenal HNF1B manifestations. RESULTS: Significant inter- and intrafamilial variability of HNF1B nephropathy has been observed. In our cohort, HNF1B pathogenic variants presented with renal cysts and diabetes syndrome (RCAD); renal cystic phenotype mimicking autosomal dominant polycystic kidney disease (ADPKD); autosomal dominant tubulointerstitial kidney disease (ADTKD) with or without hyperuricemia and gout; CAKUT; and nephrogenic diabetes insipidus (NDI). Of note, for the first time, we describe the occurrence of medullary sponge kidney (MSK) in a family harboring the HNF1B whole-gene deletion at chromosome 17q12. Genotype characterization led to the identification of an additional 6 novel HNF1B pathogenic variants, 3 frameshift, 2 missense, and 1 nonsense. CONCLUSION: HNF1B nephropathy may present with a highly variable renal phenotype in adult patients. We expand the HNF1B renal clinical picture to include MSK as a potential new finding. Finally, we expand the allelic repertoire of the disease by adding novel HNF1B pathogenic variants.

Should isolated Pseudo-Bartter syndrome be considered a CFTR-related disorder of infancy?

BACKGROUND: Infants that are negative to cystic fibrosis (CF) newborn screening (NBS) programs, or in countries without NBS, may present with metabolic alkalosis and severe salt depletion, a well-known clinical manifestation of CF termed Pseudo-Bartter syndrome (PBS). Here, we report the cases of three CF-negative children, who carry rare mutations in the CF transmembrane conductance regulator (CFTR) gene, and, for whom, PBS was the only manifestation of CFTR protein dysfunction. There is no diagnostic label for these cases. METHODS: Medical records of patients followed at our Cystic Fibrosis Centre were revised and data were collected for all patients who presented with an isolated PBS. The syndrome was defined as an episode of dehydration with low levels of serum sodium (<134mmol/L), potassium ( <3.4mmol/L), and chloride ( <100mmol/L), with metabolic alkalosis (bicarbonatemia >27mmol/L) in the absence of renal tubulopathy. RESULTS: Three out of 73 (4%) CF infants presented with a severe metabolic alkalosis with salt depletion; two of these required admission to the intensive care unit. Two infants had a negative NBS, and one was identified as a CF carrier. Sweat test was repeatedly in the negative/borderline ranges for all patients. Less than two CF causing mutations were identified (F508del/R1070W, F508del; L467F/P5L, R1066H/P5L). During a mean follow-up of 9 years, the children had no other CF manifestations. CONCLUSION: We suggest that PBS as the sole manifestation of CFTR dysfunction might be considered a CFTR-related disorder of infancy.

Congenital Hypopigmentary Disorders with Multiorgan Impairment: A Case Report and an Overview on Gray Hair Syndromes.

The term congenital hypopigmentary disorders refers to a wide group of heterogeneous hereditary diseases, clinically characterized by inborn pigmentary defects of the iris, hair, and/or skin. They include Gray Hair Syndromes (GHSs), a rare group of autosomal recessive genodermatosis hallmarked by inborn silvery gray hair. GHSs encompass Griscelli, Chediak⁻Higashi, Elejalde, and Cross syndromes, which are all characterized by a broad spectrum of severe multisystem disorders, including neurological, ocular, skeletal, and immune system impairment. In this manuscript, we describe in detail the clinical, trichoscopic, and genetic features of a rare case of Griscelli syndrome; moreover, we provide an overview of all the GHSs known to date. Our report highlights how an accurate clinical examination with noninvasive methods, like trichoscopy, may play a crucial rule in diagnosis of rare and potentially lethal genetic syndromes such as Griscelli syndrome, in which timely diagnosis and therapy may modify the clinical course, quality of life, and likelihood of survival.

[Molecular diagnosis of ADPKD]. / ADPKD: diagnosi molecolare.

Most patients with ADPKD do not need molecular genetic testing. When indicated, Sanger sequencing is the most commonly used technique. When a pathogenic mutation is not identified by Sanger, multiplex ligation-dependent probe amplification analysis (MLPA) should be performed to detect gene rearrangement (insertion or deletion). The next generation sequencing (NGS) techniques can provide high-throughput and comprehensive diagnostic screening at lower cost. Finally, in the future, targeted (TS) or whole exome sequencing (WES) will likely play a role in the molecular diagnostics of ADPKD. Molecular genetic testing is indicated in several conditions: no family history; equivocal/atypical renal imaging; marked discordant disease within family; early and severe PKD; reproductive counseling and pre-implantation genetic diagnosis; related living donor transplantation.

[Genetics and genetic counseling]. / Genetica e counseling genetico.

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is the most frequent genetic disease, characterized by progressive development of bilateral renal cysts. Two causative genes have been identified: PKD1 and PKD2. ADPKD phenotype is highly variable. Typically, ADPKD is an adult onset disease. However, occasionally, ADPKD manifests as very early onset disease. The phenotypic variability of ADPKD can be explained at three genetic levels: genic, allelic and gene modifier effects. Recent advances in molecular screening for PKD gene mutations and the introduction of the new next generation sequencing (NGS)- based genotyping approach have generated considerable improvement regarding the knowledge of genetic basis of ADPKD. The purpose of this article is to provide a comprehensive review of the genetics of ADPKD, focusing on new insights in genotype-phenotype correlation and exploring novel clinical approach to genetic testing. Evaluation of these new genetic information requires a multidisciplinary approach involving a nephrologist and a clinical geneticist.

Severe congenital neutropenia due to G6PC3 deficiency: early and delayed phenotype in two patients with two novel mutations.

Severe Congenital Neutropenia type 4 (SCN4, OMIM 612541) is a rare autosomal recessive disease due to mutations in the G6PC3 gene. The phenotype comprises neutropenia of variable severity and other anomalies including congenital heart defects, prominent superficial veins, uro-genital anomalies, facial dysmorphism, growth and developmental delay and intermittent thrombocytopenia. In some patients, SCN represents the only manifestation of the disease. Variable findings have been reported at bone marrow examination ranging from a maturation arrest at the myelocyte/promyelocyte stage (either in a hypocellular or hypercellular context) to myelokathexis. Here we report two patients harbouring two novel mutations in the G6PC3 gene, including the first Italian patient even described. Both the patients share profound neutropenia with severe infections early in life; in one case non-hematopoietic stigmata of the syndrome, including evident facial dysmorphism and vascular anomalies, appeared gradually over time, prominently in the second decade. Therefore, G6PC3 defects should be considered in any case of congenital, unexplained neutropenia regardless of the clinical phenotype. Both patients are on G-CSF treatment with no evidence of malignant evolution. Even if G6PC3 deficiency seems not to have a propensity towards malignancy, a careful evaluation is warranted.

Familial exudative vitreoretinopathy caused by a homozygous mutation in TSPAN12 in a cystic fibrosis infant.

Familial exudative vitreoretinopathy (FEVR) is a genetic disease affecting the vascularization of the peripheral retina. The clinical manifestations are very heterogeneous, ranging from mildly affected patients, who could present no visual defects, to severe conditions which can also cause complete blindness at birth or in the first decade. FEVR can be inherited in all the three genetic forms: dominant, recessive and X-linked. To date, four genes have been associated with the condition: TSPAN12. NDP. FDZ4 and LRP5. Interestingly, mutations in TSPAN12 have been considered causative of both a dominant and recessive inheritance and a FEVR phenotype sensitive to the number of TSPAN12 mutations has been supposed. Here we describe a case of a female infant affected by cystic fibrosis and by a severe form of exudative vitreoretinopathy. In particular, we have detected the homozygous missense mutation c.668 T > C in TSPAN12. Neither of the heterozygous parents has ocular manifestations of the disease, suggesting a classic recessive mendelian pattern of inheritance.

Prenatal presentation and postnatal evolution of a patient with Jansen metaphyseal dysplasia with a novel missense mutation in PTH1R.

Wave-shaped ribs were detected at prenatal ultrasound in a 20(+1) week female fetus. At birth, skeletal radiographs showed marked hypomineralization and suggested hypophosphatasia. However, elevated blood calcium and alkaline phosphatase excluded hypophosphatasia and raised the possibility of Jansen metaphyseal dysplasia. Molecular analysis of the PTH/PTHrP receptor gene (PTH1R) showed heterozygosity for a previously undescribed transversion variant (c.1373T>A), which predicts p.Ile458Lys. In vitro evaluation of wild type and mutant PTH/PTHrP receptors supported the pathogenic role of the p.Ile458Lys substitution, and confirmed the diagnosis of Jansen metaphyseal dysplasia. This disorder may present prenatally with wavy ribs and in the newborn with hypomineralization, and may therefore be confused with hypophosphatasia. The mottled metaphyseal lesions typically associated with this disease appear only in childhood.

A novel primary human immunodeficiency due to deficiency in the WASP-interacting protein WIP.

A female offspring of consanguineous parents, showed features of Wiskott-Aldrich syndrome (WAS), including recurrent infections, eczema, thrombocytopenia, defective T cell proliferation and chemotaxis, and impaired natural killer cell function. Cells from this patient had undetectable WAS protein (WASP), but normal WAS sequence and messenger RNA levels. WASP interacting protein (WIP), which stabilizes WASP, was also undetectable. A homozygous c.1301C>G stop codon mutation was found in the WIPF1 gene, which encodes WIP. Introduction of WIP into the patient's T cells restored WASP expression. These findings indicate that WIP deficiency should be suspected in patients with features of WAS in whom WAS sequence and mRNA levels are normal.

Clinical and molecular description of a Wilms tumor in a patient with tuberous sclerosis complex.

We report on a girl affected with tuberous sclerosis, carrying a germline de novo TSC2 mutation, c.4934-4935delTT, leading to a p.F1645CfsX7, who developed a unilateral Wilms tumor (WT). Molecular investigation of the tumor biopsy at diagnosis revealed the loss of the constitutional wild-type TSC2 allele, and loss of heterozygosity for the WT1 gene. Deletion of the WTX gene was also present, but it involved the functionally inactive X chromosome. No mutation affecting the remaining WT1 and WTX alleles, as well as the CTNNB1 gene was found. Pathological examination of the surgical specimen documented the presence of diffuse anaplasia and p53 immunoreactivity. To the best of our knowledge, this is the second report of a patient with tuberous sclerosis who developed a WT, and it represents the first case in which a detailed clinical and molecular description is provided.

Population genetic screening for alpha1-antitrypsin deficiency in a high-prevalence area.

BACKGROUND: Current guidelines for α1-antitrypsin deficiency (AATD) state that adult population screening should only be done in high-risk areas. Up-to-date genetic methods are always recommended. OBJECTIVES: To determine the prevalence of AATD in a suspected high-risk area by population screening, applying new genetic analyses and comparing the prevalence of liver and lung abnormalities in subjects with or without AATD. METHODS: Adult residents of Pezzaze, a village in an Italian alpine valley, voluntarily participated in the screening, and were examined for: nephelometric α1-antitrypsin (AAT) serum level, DNA analysis (mutagenic polymerase chain reaction and restriction fragment length polymorphism tests for Z and S AATD causative mutations, and denaturing high-performance liquid chromatography and/or direct gene sequencing if needed), serum aspartate and alanine transaminases, a respiratory questionnaire and the Medical Research Council dyspnea index scale. The prevalence of AATD was compared with that expected in Italy (Hardy-Weinberg equilibrium), and transaminases and the prevalence of respiratory symptoms were compared between study groups. RESULTS: Of 1,353 residents, 817 (60.4%) participated; 67 (8.2%) had low AAT serum levels (<90 mg/dl); 118 were carriers of AATD-associated alleles, 4 (0.5%) homozygotes or compound heterozygotes (1 Z, 1 S, 2 ZP(brescia)), 114 (14%) heterozygotes (46 Z, 52 S, 9 P(brescia), 4 M(wurzburg), 2 I, 1 P(lowell)). The prevalence and frequency of all AATD-related alleles was higher than expected for Italy (p < 0.001). There were no differences in symptoms of respiratory disease and transaminases between individuals with normal and low serum AAT. CONCLUSION: The screening design is one of the main strengths of this study. The large number of mostly asymptomatic individuals with AATD identified suggests that in high-risk areas adult population screening programs employing the latest genetic methods are feasible. Early recognition of individuals at risk means primary or secondary prevention measures can be taken.

G-CSF treatment of severe congenital neutropenia reverses neutropenia but does not correct the underlying functional deficiency of the neutrophil in defending against microorganisms.

The treatment of children affected by severe congenital neutropenia (SCN) with G-CSF strongly reduces the risk of sepsis by reversing neutropenia. However, SCN patients who respond to the treatment with the growth factor still have an elevated risk of succumbing to sepsis. Because the disease is usually caused by heterozygous mutations of ELA2, a gene encoding for neutrophil elastase (NE), we have investigated in G-CSF-responder and nonresponder patients affected by SCN the expression of polypeptides that constitute the antimicrobial machinery of these cells. In peripheral blood-derived neutrophils of patients with heterozygous mutations of ELA2 who were treated with G-CSF, NE was nearly absent as detected by immunofluorescence and immunoblotting, suggesting that production of the mutant protein interferes with normal gene expression. This defect was associated with abnormal expression of other granule-associated proteins such as myeloperoxidase, lactoferrin, cathepsin G, and human-neutrophil-peptide. Moreover, in one patient with partial response to G-CSF, we observed an impairment of neutrophil antimicrobial activity against Candida albicans, and, to a lower extent against Escherichia coli. Thereby, we propose that the treatment with G-CSF is not sufficient to correct all of the functional deficiency of neutrophils, and this might account for the consistent risk of infections observed in SCN patients.

Cytokine-mediated signalling and early defects in lymphoid development.

PURPOSE OF REVIEW: The aim of the review is to report on recent advances in cytokine-mediated signalling, as illustrated by the study of natural human mutants. In particular, the role of cytokines and cytokine-mediated signalling in human T-cell development is analysed in detail, and currently available forms of treatment including experimental trials are described. RECENT FINDINGS: Defects of the cytokine/JAK/STAT axis have been recently described as responsible for human Severe Combined Immune Deficiency. In particular, defects in gammac, JAK3 and IL7RA have been analysed in terms of development of novel diagnostic tools as well as of new therapeutic agents for the treatment of autoimmune diseases and graft-versus-host disease. SUMMARY: Dissection of the genetic defects underlying the various forms of Severe Combined Immune Deficiency has helped develop new and more accurate diagnostic assays and novel forms of treatment.