Rubinstein–Taybi syndrome (RSTS) is a rare autosomal dominant neurodevelopmental disorder linked to haploinsufficiency of CREBBP (RSTS1) and EP300 (RSTS2) genes. Characteristic features often include distinctive facial traits, broad thumbs and toes, short stature, and various degrees of intellectual disability. The clinical presentation of RSTS is notably variable, making it challenging to establish a clear genotype–phenotype correlation, except for specific variants which cause the allelic Menke–Hennekam syndrome. Trio exome analysis, data collection via networking and GeneMatcher platforms, transcript processing analysis, and DNA methylation profiling were performed. We identified two unrelated patients with de novo variants in EP300 (NM_001429.4: c.3671+5G>C; c.3671+5_3671+8delGTAA) predicted to cause in‐frame exon 20 skipping, confirmed in one patient. In silico 3D protein modeling suggested that exon 20 deletion (comprising 27 amino acids) likely alters the structural conformation between the RING_CBP‐p300 and HAT‐KAT11 domains. Clinically, both patients displayed severe RSTS2‐like clinical features, including autism spectrum disorder, speech delay, hearing loss, microcephaly, developmental delay, and intellectual disability, alongside ocular, respiratory, and cardiovascular abnormalities. Additionally, one patient developed early‐onset colorectal cancer. DNA methylation profiling in Subject #1 confirmed RSTS but did not align with the specific episignatures for RSTS1 or RSTS2. We propose that skipping of exon 20 in EP300 is associated with a distinct form of Rubinstein–Taybi syndrome featuring clinical characteristics not fully aligning with RSTS1 or RSTS2. Our findings increase the understanding of RSTS genetic and molecular basis and stress the need for further research to establish definitive genotype–phenotype correlations.

TANGO2 deficiency disorder is a rare autosomal recessive disease (~100 cases reported worldwide). Despite being caused by loss-of-function variants in the TANGO2 gene, patients exhibit marked phenotypic variability, including intrafamilial differences among individuals carrying identical variants. To uncover potential modifier mechanisms influencing disease severity, we developed an integrative Systems biology framework, combining exome sequencing, transcriptomics, variant effect prediction, and Human Phenotype Ontology mapping. This approach was applied to two siblings carrying identical compound heterozygous TANGO2 variants but opposite clinical outcomes: one severely affected and one asymptomatic. Personalized protein–protein interaction networks and combined univariate and multivariate analyses were employed to maximize specificity in this single-family comparison. In the affected sibling, a cumulative burden of common APOB variants, together with altered VLDLR, NTN1, and LDHA expression, implicated disrupted lipid metabolism and neurodevelopmental pathways. The asymptomatic sibling harbored a potentially protective 3′-UTR variant in EP300 and no APOB variant burden, supporting enhanced post-transcriptional regulation within developmental biology networks. These findings highlight lipid metabolism as a key pathway in TANGO2 deficiency pathophysiology and suggest autophagy and mitophagy as additional modifier mechanisms influencing phenotypic variability. Our integrative multi-omics framework provides a valuable strategy for elucidating genotype-phenotype relationships in rare diseases and supports personalized therapeutic approaches.

TANGO2-deficiency disorder (TDD) is a rare autosomal recessive condition characterised by neurodevelopmental delay, TANGO2 spells, life-threatening metabolic crises, and cardiac arrhythmias. Genotype–phenotype correlations remain poorly defined and the neurobehavioural profile of affected individuals is largely unexplored. We conducted a retrospective multicentre study of five Italian patients with genetically confirmed TDD, identified between June 2023 and May 2025. Clinical, neurophysiological, neuroimaging, genetic, and neurodevelopmental data were collected. Adaptive functioning, cognitive ability, and behavioural profiles were assessed using standardised instruments. All five patients carried biallelic TANGO2 mutations, including two previously unreported variants. Clinical severity ranged from an asymptomatic individual under preventive therapy to a fatal early-onset metabolic crisis. Marked intrafamilial variability was observed in two siblings sharing the same genotype. Systematic neurodevelopmental assessment revealed a spectrum of cognitive and adaptive outcomes, with attentional difficulties identified as a recurrent feature. No metabolic crises or TANGO2 spells were documented following initiation of B-vitamin and cofactor supplementation in surviving patients. This cohort expands the mutational and phenotypic spectrum of TDD and highlights the diagnostic value of TANGO2 testing in patients with neurodevelopmental delay or paroxysmal neurological episodes, even in the absence of metabolic crises. Early supplementation therapy may contribute to clinical stability, though prospective controlled studies are needed.

Background: SATB2-associated syndrome (SAS), also known as Glass syndrome, is a neurodevelopmental disorder (NDD) characterized by intellectual disability, developmental delay, absent or limited speech, and distinctive craniofacial and dental anomalies. It is caused by autosomal dominant pathogenic variants in the SATB2 gene, which plays a crucial role in brain, dental, and jaw development. Due to its variable phenotype, clinical diagnosis can be challenging, necessitating genetic confirmation. Methods: We present six new cases of SAS with SATB2 germline variants identified through next generation sequencing (NGS) technologies, expanding the known genetic and clinical spectrum of the syndrome. Detailed clinical phenotyping was performed for all patients. Results: Our cohort exhibits a broad range of clinical manifestations consistent with SAS, encompassing severe intellectual disability, profound speech delay, various palatal and dental abnormalities. We report the oldest adult patient (56 years old) carrying an in-frame duplication, and a pediatric patient with a missense variant who presented a significant reduction in visual acuity, likely of neurological or cortical origin, in the absence of ophthalmological abnormalities. SATB2 variants include three missenses, two in-frame deletion/duplication and one frameshift variant, several of which are novel and classified as likely pathogenic or pathogenic according to ACMG guidelines. Conclusions: This report provides new clinical and genetic insights into the landscape of SAS. Our findings confirm the phenotypic heterogeneity of SAS and highlight the critical role of comprehensive genetic testing for accurate diagnosis in NDD patients.