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BACKGROUND AND AIMS The approach to Alport syndrome is a difficult task due to the phenotypic variability of its symptomatology, incomplete penetrance and its different forms of inheritance [1]. It presents a high degree of underdiagnosis, both because of erratic diagnosis as well as the existence of undiagnosed patients [2]. This study shows a patient carrying two pathogenic variants in COL4A3 and COL4A4 genes, respectively. The interest of the case lies in the low reported frequency of this type of inheritance, of which there are still no prevalence studies, but which may help to better understand this entity, as well as aid future diagnoses [3, 4]. METHOD Our index case is a 55-year-old male (IV.1). His medical history dates back to childhood when the disease began with microhematuria, repeated urinary tract infections, proteinuria and a progressive decrease in glomerular filtration rate until he required hemodialysis at 23 years. He received a living-renal transplantation from his mother, restarting hemodialysis at 49 years; a second engraftment was carried out 3 years later that was working for 5 years until a clear cell renal cancer was diagnosed and transplantectomy was required. There was no evidence of hearing or ocular impairment. Throughout the patient's follow-up, the existence of other relatives on the paternal side with kidney disease became known, and with the suspicion of hereditary origin, a genogram of the family was constructed with five generations [Figure 1]. A genetic study was performed using a next-generation sequencing (NGS) panel (Sophia Genetics) covering the coding and splicing regions of 44 genes related to HRE (Table 1). Subsequently, the study was extended to other relatives. RESULTS Molecular analysis identified two probably pathogenic variants in our index case and other relative at the moment, both in heterozygosis, one in exon 48 of the COL4A3 gene: c.4421T > C, p.(Leu1474Pro). This is a missense-type change in which thymine is replaced by cytosine at position 4421 of the coding sequence and predicts the substitution of the amino acid leucine by proline at position 1474 of the protein, affecting two functional domains. This variant is described and reported in the databases as pathogenic. On the other hand, it presents a deletion, also in heterozygosis, of exon 9 of the COL4A4 gene. Both variants were confirmed by Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA), respectively. In this family, the variants co-segregate with the disease, although the analysis of other cases would be useful; furthermore, both variants co-segregate together, which indicates that the variants are in cis and both come from the same branch and neither has a de novo origin. CONCLUSION We have identified a case of digenic inheritance, two pathogenic variants in COL4A3 and COL4A4 genes respectively, thanks to the NGS techniques, of which very few cases have been described in the literature. Genetic analysis is the only way to confirm the diagnosis, often even to establish it after uncertain diagnoses; it is also the way to determine the mode of transmission and can often avoid the use of other invasive and not risk-free techniques such as skin or kidney biopsy. Although there is currently no curative treatment, early diagnosis is important to slow its progression, so that after the identification of a pathogenic variant, the family implications should be of special interest, to carry out adequate genetic counseling where family members at risk are informed and genetic study is offered, as well as the existing reproductive options for affected patients, such as preimplantation genetic testing or gamete donation. Otherwise, the offspring should be included in a program for early detection and monitoring of the disease.

Background and Aims Despite advances in understanding the underlying causes of CKD, 20% of cases remain unexplained (1). A genomic approach has the potential to identify the cause of CKD in a significant portion of pediatric and adult patients, with estimated diagnostic rates of 5-30% (2). However, there is a lack of consensus in the scientific community on the best diagnostic algorithm. The DECIDE project (Diagnostic EffiCacy kIdney Disease European) is a European collaboration that aims to address this issue by evaluating the diagnostic rate of a targeted gene panel in a large cohort of patients. Method DECIDE involved three Italian and two Spanish centers, encompassing both pediatric and adult patients. The study used the Nephropathies Solution Panel (NES, SOPHiA Genetics), which covers 44 kidney-related genes, to test patients with a high suspicion of genetic kidney disease. The clinical presentation was classified into cystic disease, glomerulopathy, CAKUT, tubulopathy, nephrocalcinosis, other, and negative phenotype. The diagnostic yield of the NES panel was calculated. To assess the genotype-phenotype relationship, Kaplan-Meier analyses were performed. Additionally, the diagnostic results obtained from alternative technologies, such as larger panels, WES and hybridization arrays, in cases of NES panel negative results, were also collected. Results As far as now the DECIDE project collected 632 genetic data. To evaluate the diagnostic accuracy of the panel, the number of (likely) pathogenic variants correlated to phenotype was analyzed. The diagnostic yield is shown in Figure 1, with 46% for cystic disease, 41% for glomerulopathy, 33% for tubulopathies, 28% for CAKUT, 14% for nephrocalcinosis, 2% for negative (in the context of segregation analyses or in cascade test) and 8% for other. Table 1 shows that the main genes involved in the diagnosis were PKD1, PKD2, COL4A3, COL4A4, and COL4A5. In patients affected by cystic disease, the mean age of kidney failure was 48 years in the presence of diagnostic variants, 59 years for VUS, and no events were reported in patients with negative tests. The Kaplan-Meier curve confirmed a worse prognosis in patients with diagnostic variants (p-value<0.05). However, no significant genotype-phenotype correlation in terms of time to replacement therapy was observed in glomerulopathic patients. In cases of non-diagnostic results, 21 further investigations were performed. An enriched panel for cystic disease didn't detect any diagnostic variants, while only one patient was diagnosed using WES. The Hybridization Array identified a gene deletion that is under investigation and may be related to the phenotype (Nephronophthisis). Conclusion The preliminary results of the DECIDE project, based on about 600 data, demonstrate the potential of the NES panel in the diagnosis of kidney genomic disease. The panel showed a good diagnostic yield for cystic disease (46%) and glomerulopathy (41%), but it appears less effective in other clinical presentations. The average diagnostic yield of the panel was comparable to published data for gene panel and WES approaches. However, additional tests such as larger gene panels, WES, or CGH-array were found to be of limited usefulness, as they only identified one pathogenic variant. These results suggest that new approaches are necessary to uncover the hidden genetic components of rare renal conditions.

Background and Aims Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary nephropathy that causes kidney failure and the need for renal replacement therapy (RRT). It has recently been established that there is a genotype-phenotype relationship for this disease, with differences in the age of access to TRS if the involvement occurs in the PKD1 or PKD2 gene and if the variant is truncating or not. Identifying patients at high risk for rapid progression has become increasingly important given the emergence of potential new treatments such as tolvaptan. Method Studies are carried out in 23 families affected in which a genetic study has previously been the variant identified. For the survival analysis, the Kaplan-Meier test was performed. Data are expressed in terms of mean ± SD, median and %. Results The data described in Table 1 show that there is huge variability of access to RRT according to the type of variant found in the family. We found families in which the age at which kidney failure occurred ranged from 48.03 (28.38-67.68) years to families in which RRT began with 78.04 (65.06-91.03). We observed that those families that present a variant with a stop or frameshift codon suffer a loss of kidney function before those that present a missense variant. In the variants with a stop or frameshift codon, we observed that they ranged from 48.03 (28.38-67.68) for the variant c.7480G> T (p.Glu2494 *) to 73.75 (61.52-85, 98) in variant c.9616C> T p.Gln3203 *. In those missense variants, the age of access to RRT ranges from 62.17 (60.43-63.91) to 77.13 (71.56-82.71) Conclusion Advances in studies of the genes involved in ADPKD are expanding the identification of new variants and the knowledge about their involvement in the progression of the disease. The correlation between genotype and kidney disease will provide a useful clinical prognosis for ADPKD and will allow us to establish current and future treatments.