Waardenburg syndrome (WS) is a common genetic cause of syndromic hearing loss, accounting for 2–5% of congenital cases. It is characterized by hearing impairment and pigmentation abnormalities in the skin, hair, and eyes. Seven genes are associated with WS: PAX3, MITF, EDNRB, EDN3, SOX10, KITLG, and SNAI2. This study investigates the genetic causes of WS in three familial cases. Whole-exome sequencing (WES) was performed to identify single nucleotide variants (SNVs). Copy number variants (CNVs) were analyzed from the WES raw data and through multiplex ligation-dependent probe amplification (MLPA). The study identified one pathogenic SNV and two novel CNVs, corresponding to type I and type II WS patterns in the three families. The SNV, a nonsense variant (c.1198C>T p.Arg400*), was found in MITF and segregated in the affected father. The two CNVs were a deletion of exon 5 in PAX3 in a family with two affected members and a large novel deletion comprising seven genes, including SOX10, in a family with three affected members. These findings confirmed a WS diagnosis through genetic testing. The study emphasizes the importance of integrating multiple genetic testing approaches for accurate and reliable diagnosis, highlighting their role in improving patient management and providing tailored genetic counseling.

In patients with 46,XY disorders of sex development (DSDs), next-generation sequencing (NGS) has high diagnostic efficiency. One contribution to this diagnostic approach is the possibility of applying reverse phenotyping when a variant in a gene associated with multiple organ hits is found. Our aim is to report a case of a patient with 46,XY DSDs in whom the identification of a novel variant in MYRF led to the detection of a clinically inapparent congenital heart defect. A full-term newborn presented with ambiguous genitalia, as follows: a 2 cm phallus, penoscrotal hypospadias, partially fused labioscrotal folds, an anogenital distance of 1.2 cm, and non-palpable gonads. The karyotype was 46,XY, serum testosterone and AMH were low, whereas LH and FSH were high, leading to the diagnosis of dysgenetic DSD. Whole exome sequencing identified a novel, heterozygous, nonsense variant in MYRF, classified as pathogenic according to the ACMG criteria. MYRF encodes a membrane-bound transcriptional factor expressed in several tissues associated with OCUGS syndrome (ophthalmic, cardiac, and urogenital anomalies). In the patient, oriented clinical assessment ruled out ophthalmic defects, but ultrasonography confirmed meso/dextrocardia. We report a novel MYRF variant in a patient with 46,XY DSDs, allowing us to identify a clinically inapparent congenital heart defect by reverse phenotyping.

Epstein Barr virus sequence variability has been deeply studied throughout the past years in isolates from various geographic regions and consequent geographic variation at both genetic and genomic levels has been described. However, isolates from South America have been underrepresented in these studies. Here, we sequenced 15 complete EBV genomes that we analyzed, by means of a custom-built bioinformatic pipeline, together with publicly available raw NGS data for 199 EBV isolates from other parts of the globe. Phylogenetic relations of the genomes, geographic structure and variability of the data set, and evolution rates for the whole genome and each gene were assessed. The present study contributes to overcome the scarcity of EBV complete genomes from South America, and hence, achieves the most comprehensive geography-related variability study by determining the actual contribution of each EBV gene to the geographic segregation of the entire genomes. Moreover, to the best of our knowledge, we established for the first time the evolution rate for the entire EBV genome, on a host-virus codivergence-independent assumption, and statistically demonstrate that evolution rates, on a gene-by-gene basis, are related to the encoded protein function. Considering evolution of dsDNA viruses with a codivergence-independent approach, may lay the basis for future research on EBV evolution. Additionally, this work also expands the sampling-time lapse of available complete genomes derived from different EBV-related conditions, a matter that until today, prevents for detailed phylogeographic analysis.

Complex genetic syndromes represent a diagnostic challenge due to their diverse phenotypic presentations, which often evolve over time and may not be fully evident at birth. Disorders of sex development (DSD) comprise congenital conditions with discordance between chromosomal, gonadal, and/or genital sex. In 46,XY gonadal dysgenesis, undervirilisation or female-appearing genitalia may occur despite a normal karyotype, and diagnosis increasingly relies on genomic approaches. Prenatal and postnatal growth failure has been described in patients with syndromic 46,XY DSD. We report a male patient with SGA, lack of postnatal catch-up growth, and syndromic dysgenetic 46,XY DSD followed longitudinally from infancy to 11 years, in whom whole-exome sequencing (WES) reanalysis revealed a pathogenic 2.7 Mb microdeletion at 3q27.1q27.2. Systematic review of previously reported 3q27.1 deletions identified overlapping phenotypes but limited documentation of gonadal dysfunction. Curation of 71 genes within the deleted region highlighted DVL3 and CLCN2 as potential contributors to the gonadal phenotype, although functional evidence remains lacking. This case expands the phenotypic spectrum of 3q27.1 microdeletion syndrome, suggesting that 46,XY gonadal dysgenesis may represent an under-recognised feature. It also underscores the importance of copy number variant (CNV) analysis and periodic re-evaluation of sequencing data to increase diagnostic yield.

Context: P450 oxidoreductase (POR) deficiency is a rare congenital adrenal hyperplasia with variable severity. The mechanisms of severe mutations and their full metabolic consequences, including drug metabolism, are not fully characterized. Objective: To define the clinical, biochemical, and molecular consequences of a novel homozygous POR missense mutation, p.Gly88Ser (G88S), identified in four unrelated Argentine families. Design: A translational study combining clinical case series analysis with comprehensive in vitro molecular and functional characterization of the novel protein variant. Setting: Tertiary pediatric endocrine centers in Argentina and Switzerland. Patients: Five individuals (four 46,XY; one 46,XX) from four unrelated families presenting with disorders of sex development and adrenal dysfunction. Main Outcome Measures: Clinical phenotypes, hormonal profiles, and POR gene sequencing. In vitro analysis of recombinant POR measured flavin content, reductase activity, and support of steroidogenic and drug-metabolizing P450s. Results: All patients were homozygous for the c.262G>A (p.G88S) mutation. This FMN-binding domain variant caused protein instability with severe loss of FMN (<30%) and FAD (<15%) cofactors. Steroidogenic activities were virtually abolished (CYP21A2: 1.3%; CYP17A1 17,20-lyase: 5.5% of wild-type), explaining the clinical phenotype. Activities of major drug-metabolizing enzymes were also severely impaired (3-9% of wild-type), establishing a “ poor metabolizer” phenotype. Conclusions: The POR G88S mutation causes one of the most severe forms of PORD described, driven by dynamic protein instability and cofactor loss. It is a critical pharmacogenomic marker, and its recurrence in Argentina suggests a potential screening target.