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.

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.

Morpho-functional survey in children suspected of inherited retinal dystrophies via video recording, electrophysiology and genetic analysis.

PURPOSE: To present a detailed study matching functional response and video imaging with genetic analysis in children suspected of inherited retinal dystrophy (IRD). METHODS: Sixteen children underwent fundus examination via video recording (Heine Omega 500 indirect ophthalmoscope with DV1 camera) and electroretinogram (ERG) under general anesthesia to investigate the cause of suspected low vision. The patients [median age 12 (interquartile range 8-57.5) months] had associated genetic analysis performed with next-generation sequencing or array-comparative genomic hybridization. RESULTS: Four children had potential pathogenic variants in genes involved in Leber congenital amaurosis and Joubert syndrome (NMNAT1, CEP290, KCNJ13, IMPDH1); 1 child had a 16p11.2 microdeletion and 1 in 2q22.1. The ERG was altered in 6 patients, fundus imaging showed serious abnormality matching an IRD in 7 children, and less severe fundus alterations were found in 2 subjects. CONCLUSION: Fundus imaging associated with ERG may be significant in IRD diagnosis and visual impairment prognosis, alongside genetic analysis and therapy in selected cases.

Autosomal Dominant Tubulointerstitial Kidney Disease with Adult Onset due to a Novel Renin Mutation Mapping in the Mature Protein.

Autosomal dominant tubulointerstitial kidney disease (ADTKD) is a genetically heterogeneous renal disorder leading to progressive loss of renal function. ADTKD-REN is due to rare mutations in renin, all localized in the protein leader peptide and affecting its co-translational insertion in the endoplasmic reticulum (ER). Through exome sequencing in an adult-onset ADTKD family we identified a new renin variant, p.L381P, mapping in the mature protein. To assess its pathogenicity, we combined genetic data, computational and predictive analysis and functional studies. The L381P substitution affects an evolutionary conserved residue, co-segregates with renal disease, is not found in population databases and is predicted to be deleterious by in silico tools and by structural modelling. Expression of the L381P variant leads to its ER retention and induction of the Unfolded Protein Response in cell models and to defective pronephros development in zebrafish. Our work shows that REN mutations outside of renin leader peptide can cause ADTKD and delineates an adult form of ADTKD-REN, a condition which has usually its onset in childhood. This has implications for the molecular diagnosis and the estimated prevalence of the disease and points at ER homeostasis as a common pathway affected in ADTKD-REN, and possibly more generally in ADTKD.

[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.

Atypical presentation of autoimmune lymphoproliferative syndrome due to CASP10 mutation.

Herein we describe the case of a 8-years-old boy with diagnosis of atypical autoimmune lymphoproliferative syndrome (ALPS), carrying heterozygous mutation of CASP10 gene (I406L). He presented with multiple non-invasive infections of the skin, that were associated to chronic non-malignant non-infectious lymphadenopathy, failure to thrive, weakness, arthralgia, relapsing oral aftosis, and expansion of TCRαß(+) CD4(-)/CD8(-) T cells. This observation suggests that cutaneous infections can be observed in ALPS patients carrying CASP10 mutations.

[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.

Toll-like receptor 3 gene polymorphisms and severity of pandemic A/H1N1/2009 influenza in otherwise healthy children.

BACKGROUND: Toll-like receptors (TLRs) form an essential part of the innate immune system, which plays a fundamental role in rapidly and effectively controlling infections and initiating adaptive immunity. There are no published data concerning the importance of polymorphisms of TLRs in conditioning susceptibility to influenza or the severity of the disease. The aim of this study was to evaluate whether selected polymorphisms of TLR2, TLR3 and TLR4 influence the incidence and clinical picture of pandemic A/H1N1/2009 influenza. RESULTS: The study involved 272 healthy children attending our Emergency Room for influenza-like illness (ILI), including 51 (18.8%) with pandemic A/H1N1/2009 influenza as revealed by real-time polymerase chain reaction, and 164 healthy controls examined after minor surgery. Genomic DNA was extracted from whole blood samples and five single-nucleotide polymorphisms (SNPs) were studied: TLR2 rs5743708, TLR3 rs5743313, TLR3 rs5743315, TLR4 rs4986790 and TLR4 rs4986791. The TLR3 rs5743313/CT polymorphism was found in all of the children with pneumonia and influenza infection, but in a significantly smaller number of those with A/H1N1/2009 influenza without pneumonia (<0.0001). TLR2, TLR3 rs5743315/AC and TLR4 polymorphisms were equally distributed in all of the groups regardless of the presence of the pandemic A/H1N1/2009 virus and clinical diagnosis. Viral load was comparable in all of the study groups. CONCLUSIONS: There is a close relationship between the presence of TLR3 rs5743313/CT and an increased risk of pneumonia in children infected by the pandemic A/H1N1/2009 influenza virus.

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 heterogeneity and diagnostic delay of autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy syndrome.

Autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) is a rare autosomal recessive organ-specific autoimmune disorder that is characterized by a variable combination of (i) chronic mucocutaneous candidiasis, (ii) polyendocrinopathy and/or hepatitis and (iii) dystrophy of the dental enamel and nails. We analyzed the AIRE (autoimmune regulator) gene in subjects who presented any symptom that has been associated with APECED, including candidiasis and autoimmune endocrinopathy. We observed that 83.3% of patients presented at least two of the three typical manifestations of APECED, while the remaining 16.7% of patients showed other signs of the disease. Analysis of the genetic diagnosis of these subjects revealed that a considerable delay occurs in the majority of patients between the appearance of symptoms and the diagnosis. Overall, the mean diagnostic delay in our patients was 10.2 years. These results suggest that molecular analysis of AIRE should be performed in patients with relapsing mucocutaneous candidiasis for early identification of APECED.

Genetic characteristics of eighty-seven patients with the Wiskott-Aldrich syndrome.

The Wiskott-Aldrich syndrome (WAS) is an X-linked recessive immune deficiency disorder characterized by thrombocytopenia, small platelet size, eczema, recurrent infections, and increased risk of autoimmune disorders and malignancies. WAS is caused by mutations in the WASP gene which encodes WASP, a 502-amino acid protein. WASP plays a critical role in actin cytoskeleton organization and signalling, and functions of immune cells. We present here the results of genetic analysis of patients with WAS from eleven Eastern and Central European (ECE) countries and Turkey. Clinical and haematological information of 87 affected males and 48 carrier females from 77 WAS families were collected. The WASP gene was sequenced from genomic DNA of patients with WAS, as well as their family members to identify carriers. In this large cohort, we identified 62 unique mutations including 17 novel sequence variants. The mutations were scattered throughout the WASP gene and included single base pair changes (17 missense and 11 nonsense mutations), 7 small insertions, 18 deletions, and 9 splice site defects. Genetic counselling and prenatal diagnosis were applied in four affected families. This study was part of the J Project aimed at identifying genetic basis of primary immunodeficiency disease in ECE countries. This report provides the first comprehensive overview of the molecular genetic and demographic features of WAS in ECE.

Impaired NK-cell migration in WAS/XLT patients: role of Cdc42/WASp pathway in the control of chemokine-induced beta2 integrin high-affinity state.

We analyzed the involvement of Wiskott-Aldrich syndrome protein (WASp), a critical regulator of actin cytoskeleton remodeling, in the control of natural killer (NK)-cell migration. NK cells derived from patients with Wiskott-Aldrich syndrome/X-linked thrombocytopenia (WAS/XLT), carrying different mutations in the WASP coding gene, displayed reduced migration through intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), or endothelial cells in response to CXCL12/stromal cell-derived factor-1 and CX3CL1/fractalkine. Inhibition of WAS/XLT NK-cell migration was associated with reduced ability of these cells to up-regulate the expression of CD18 activation neoepitope and to adhere to ICAM-1 or VCAM-1 following chemokine stimulation. Moreover, chemokine receptor or beta1 or beta2 integrin engagement on NK cells rapidly resulted in Cdc42 activation and WASp tyrosine phosphorylation as well as in WASp association with Fyn and Pyk-2 tyrosine kinases. NK-cell pretreatment with wiskostatin, to prevent Cdc42/WASp association, impaired chemokine-induced NK-cell migration through ICAM-1 and beta2 integrin activation-dependent neoepitope expression. These results show that the Cdc42/WASp pathway plays a crucial role in the regulation of NK-cell migration by acting as a critical component of the chemokine-induced inside-out signaling that regulates lymphocyte function-associated antigen-1 function and suggest that after integrin or chemokine receptor engagement WASp function is regulated by the coordinate action of both Cdc42 and tyrosine kinases.