Thanks to a long-read sequencing (LRS) approach, in this study, we have reported a molecularly solved case of a proband with a clinical diagnosis of Cornelia de Lange syndrome (CDLS), which is a multisystemic disorder whose causative molecular defects involve cohesin complex genes, with NIPBL located at 5p13.2 accounting for approximately 50%–60% of CDLS cases. The first-tier tests revealed an abnormal karyotype 46,XY,t(5;15)(p13;q25)dn and a preserved NIPBL sequencing. Copy number variants (CNVs) at the translocation breakpoints, in disease genes, or in probably pathogenic loci were excluded by a-CGH analysis. Through fluorescence in situ hybridization (FISH) analysis on derivative chromosome 5, the breakpoint was relocated 3 Mb far from NIPBL 5′UTR, which seemed fully maintained as FISH-probe mapping to the gene showed no split signals. Moreover, tri-color FISH revealed an apparently balanced paracentric inversion including NIPBL on derivative 5. Based on the strong clinical suspicion, we evaluated the NIPBL transcript by RT-qPCR that revealed a normal amount of transcript till exon 22 and a halved amount of the transcript from exon 23 to 3′UTR, indicating the expression of a truncated transcript probably leading to a defective protein. Despite RT-qPCR confirmed the patient’s CDLS clinical diagnosis, the molecular mechanism underlying this event remained to be an unsolved challenge for years. The LRS approach with nanopore technologies was able to fill the gap in this complex scenario and highlighted a chromothripsis event marked out at 5p13.2 by 36 breaks clustered in a 7.3-Mb region. The NIPBL gene was disrupted by 16 breaks and the resulting fragments were relocated in different positions and orientations. LRS confirmed the previous findings, and it has been proven to be crucial to define the complex chromosomal rearrangement in this patient which escaped current diagnostic investigations. Its application in the clinical practice will contribute to solve the unsolved.

Background: The STAG1 gene has been related to a poorly known form of intellectual disability, known as Intellectual Developmental Disorder, Autosomal Dominant 47 (MRD47). Functionally, MRD47 is part of the Cohesinopathies, a small family of rare genetic disorders caused by defective cohesin complex, whose activity is essential for sister chromatid cohesion and therefore for chromatin organization. Chromatin state modulation is an entangled process finely modulated by a large number of actors that, if altered, give rise to the so-called Chromatinopathies. The clinical and biological overlap among these families of conditions on one hand poses significant challenges during diagnostic definition, and, on the other, may help delineate more accurate management guidelines. Methods: Starting from the report of a novel pathogenic variant in the STAG1 gene, we performed a retrospective clinical and molecular review of all previously reported patients affected by this rare disorder. Once clinical and photographic data of all published patients were collected, we used Face2Gene deep learning technology to analyze STAG1 facial phenotype, comparing it to both Chromatinopathy and Cohesinopathy profiles. Results: Our clinical and molecular re-evaluation of reported cases confirms MRD47 as a mainly neurodevelopmental disorder. Through artificial intelligence technology, we were able to first create the gestaltic profile of MRD47. Face2Gene analyses of this composite phenotype, although limited by the tool’s analysis modalities, demonstrates the strong overlap of STAG1 disorder with Chromatinopathies. Conclusions: The present literature review, together with gestaltic analyses of the STAG1-related phenotype, underscores the strong resemblance of MRD47 to epigenetic machinery disorders. The present case brings to light once more the biological and phenotypical entanglement of Cohesinopathies and Chromatinopathies, hinting at STAG1 as the joining chain.

Background Neurodevelopmental disorders, hypotonia, microcephaly or macrocephaly, poor growth and distinctive facial traits are some of the most common reasons to refer a child to an expert consultant. But which expert? A priori response might not be always predictable. Clinical experience teaches that it is not unusual to come across a metabolic diagnosis in a patient suspected of a genetic condition and vice versa. Still, although phenotypically convergent, genetic and metabolic disorders strongly diverge on therapeutic availability. In such an entangled scenario, new sequencing technologies may bring to light further uncertainties, detecting variants that often need a clinical confirm to be interpreted. Methods. In order to explore clinical convergence among metabolic and genetic disorders we present a cases’ collection of patients wrongly referred to metabolic disorder clinic or to medical genetic service in a third level Center in the North of Italy. Results. Data gained from this retrospective review demonstrate the striking importance of multi-disciplinary management of complex pediatric cases. Conclusions. In Hub Hospitals and in rare diseases’ Centers, it appears mandatory to promote a side by side collaboration embracing pediatricians, clinical geneticists and laboratory in order to take an all-around point of view of undiagnosed patients. What falls out of our competence might fall out of our view as well.