Lidia Pezzani

Background: Whole-Exome Sequencing (WES) and Whole-Genome Sequencing (WGS) can improve the diagnostic journey of paediatric patients with rare diseases by reducing the ‘diagnostic odyssey’ and increasing diagnostic yield (DY). However, the economic impact of implementing these technologies as first-tier tests in clinical practice and the identification of the most appropriate strategy for different patient types remain unclear. Methods: We performed a micro-costing analysis in three European centres of excellence for rare diseases to estimate DY, total diagnostic pathway costs, and cost per diagnosed patient across different diagnostic scenarios for two patient groups: critically ill inpatients and outpatients with neurodevelopmental delays. Results: For inpatients, first-tier WGS was projected to reduce costs per diagnosed patient by 85–98% (€251,656- €1,968,669 savings per diagnosis), compared with sequential genetic testing, mainly due to shorter neonatal intensive care unit stays until the diagnostic endpoint. For outpatients, first-tier WGS produced the lowest expected cost per diagnosis in one of three centres, reducing costs per diagnosed patient by 57% (€11,258 savings per diagnosis), compared with last-tier use or use of large clinical panels. In the remaining two centres, the most convenient strategy was first-tier WES, reducing costs per diagnosed patient by 9–46% (€762-€3,579 savings per diagnosis). Conclusions: These findings support a stratified first-tier sequencing approach in which WGS is prioritised for critically ill inpatients due to its superior clinical and economic value, while WES remains a pragmatic and cost-effective first-tier option for many outpatient pathways. As sequencing costs continue to decline and analytical capabilities expand, WGS is expected to become increasingly advantageous across settings.

Neuropediatric rare diseases comprise a huge spectrum of clinically heterogeneous conditions, often recognizing a genetic basis

Glycogen storage disorders are a group of genetic disorders affecting glucose homeostasis in the body. Muscular glycogen stores are essential for liberating glucose for energy supply during bursts of activity and sustained muscle work. Muscle glycogen storage disease 0 (GSD0B) is associated with biallelic variants in GYS1 causing muscular glycogen synthetase deficiency and has previously been identified as a cause of sudden cardiac arrest in childhood. Muscle biopsies of affected living relatives demonstrated a paucity of glycogen staining. We describe 10 individuals from seven families to document the evolution of cardiac disease in individuals identified through cascade testing. This study expands knowledge of the clinical phenotype of muscular GSD type 0 to include adult survivors with myopathy and further describes the natural history of cardiac manifestations.

Mendelian disorders of the epigenetic machinery (MDEMs) include a large number of conditions caused by defective activity of a member of the epigenetic machinery. MDEMs are characterized by multiple congenital abnormalities, intellectual disability and abnormal growth. that can be variably up- or down-regulated. Background/Objectives: In several MDEMs, a predisposition to metabolic syndrome and obesity since childhood has been reported. Methods: To investigate the metabolic bases of this abnormal growth, we collected physical data from a heterogeneous pool of 38 patients affected by MDEMs. Thirty-five patients performed indirect calorimetry (as a measure of resting energy expenditure, REE) and blood tests to monitor plasmatic nutritional parameters. Conclusions: Although limited by a small-sized and heterogeneous sample, our study demonstrates a linear correlation between REE and physical parameters, OFC, height and weight, and observed a slight imbalance on several plasmatic spies of metabolic syndrome predisposition. Furthermore, we demonstrated a significantly higher REE in Sotos Syndrome type 1 patients compared to the controls, which resulted independent from height, suggesting that impaired metabolism in these patients may go beyond overgrowth.

Background/Objectives: The pathogenetic role of 15q11.2 Copy Number Variations (CNVs) remains contentious in the scientific community, as microdeletions and microduplications in this region are linked to neurodevelopmental disorders with variable expressivity. This study aims to explore the diagnostic utility of Exome Sequencing (ES) in a cohort of pediatric patients with 15q11.2 CNVs. Methods: We enrolled 35 probands with 15q11.2 microdeletions or microduplications from two genetic centers between January 2021 and January 2023. Chromosomal Microarray Analysis (CMA) and ES were performed with written consent obtained from all parents. Pathogenic variants were classified according to ACMG guidelines. Results: CMA identified additional pathogenic CNVs in 3 of 35 children (9%). Subsequent ES revealed likely pathogenic or pathogenic variants in 11 of 32 children (34%). Notably, a higher percentage of isolated autism spectrum disorder (ASD) diagnoses was observed in patients without other CNVs or point mutations (p = 0.019). Conclusions: The ES analysis provided a diagnostic yield of 34% in this pediatric cohort with 15q11.2 CNVs. While the study does not dismiss the contribution of the CNV to the clinical phenotype, the findings suggest that ES may uncover the underlying causes of neurodevelopmental disorders. Continuous monitoring and further genetic testing are recommended for all 15q11.2 CNV carriers to optimize clinical management and familial counseling.

DYRK1A-related intellectual disability is a recently described syndrome characterized by microcephaly, global developmental delay, impaired speech development, and distinctive facial features, which let to define it as a recognizable syndrome. Here we report four new patients of different ethnicity, broadening the clinical phenotype of the condition and highlighting how ethnic influences in the facial appearance could make it less recognizable.

Whole-exome sequencing (WES) is a powerful and comprehensive tool for the genetic diagnosis of rare diseases, but few reports describe its timely application and clinical impact on infantile cardiomyopathies (CM). We conducted a retrospective analysis of patients with infantile CMs who had trio (proband and parents)-WES to determine whether results contributed to clinical management in urgent and non-urgent settings. Twenty-nine out of 42 enrolled patients (69.0%) received a definitive molecular diagnosis. The mean time-to-diagnosis was 9.7 days in urgent settings, and 17 out of 24 patients (70.8%) obtained an etiological classification. In non-urgent settings, the mean time-to-diagnosis was 225 days, and 12 out of 18 patients (66.7%) had a molecular diagnosis. In 37 out of 42 patients (88.1%), the genetic findings contributed to clinical management, including heart transplantation, palliative care, or medical treatment, independent of the patient’s critical condition. All 29 patients and families with a definitive diagnosis received specific counseling about recurrence risk, and in seven (24.1%) cases, the result facilitated diagnosis in parents or siblings. In conclusion, genetic diagnosis significantly contributes to patients’ clinical and family management, and trio-WES should be performed promptly to be an essential part of care in infantile cardiomyopathy, maximizing its clinical utility.

X‐linked intellectual disability (XLID) refers to a clinically and genetically heterogeneous neurodevelopmental disorder, in which males are more heavily affected than females. Among the syndromic forms of XLID, identified by additional clinical signs as part of the disease spectrum, the association between XLID and severe myopia has been poorly characterized. We used whole exome sequencing (WES) to study two Italian male twins presenting impaired intellectual function and adaptive behavior, in association with severe myopia and mild facial dysmorphisms. WES analysis detected the novel, maternally inherited, mutation c.916G > C (G306R) in the X‐linked heparan sulfate 6‐O‐sulfotransferase 2 (HS6ST2) gene. HS6ST2 transfers sulfate from adenosine 3′‐phosphate, 5′‐phosphosulfate to the sixth position of the N‐sulphoglucosamine residue in heparan sulfate (HS) proteoglycans. Low HS sulfation levels are associated with defective optic disc and stalk morphogenesis during mammalian visual system development. The c.916G>C variant affects the HS6ST2 substrate binding site, and its effect was considered “deleterious” by in‐silico tools. An in‐vitro enzymatic assay showed that the HS6ST2 mutant isoform had significantly reduced sulphotransferase activity. Taken together, the results suggest that mutant HS6ST2 is possibly involved in the development of myopia and cognitive impairment, characteristics of the probands reported here.