Previous reports have described a spectrum of clinical phenotypes in patients with MED25 pathogenic variants. One specific phenotype is the Basel-Vanagaite-Smirin-Yosef syndrome, which is a rare, autosomal recessive disorder characterized by a wide range of symptoms including eye abnormalities, cardiac abnormalities, palatal abnormalities, intellectual disability, and epilepsy. Although epilepsy appears to be common, the electroclinical phenotypes of patients with Basel-Vanagaite-Smirin-Yosef syndrome have not been well described. Here, we report 3 Basel-Vanagaite-Smirin-Yosef syndrome patients from 2 families of Lebanese descent with a homozygous MED25 founder variant from Alberta Children's Hospital, Calgary, Alberta. We describe in detail electroclinical phenotypes in each of these 3 patients. These patients developed seizures with onset between 2 and 3 years of age, multifocal and generalized discharges, as well as photoparoxysmal responses on electroencephalogram. We review the relevance of these epilepsy findings in the context of other published reports of Basel-Vanagaite-Smirin-Yosef syndrome.

Mediator of RNA polymerase II transcription subunit 25 (MED25), a crucial component of the transcriptional coactivator complex, plays a significant role in the transcription of most RNA polymerase II-dependent genes. Mutations in MED25 have been linked to various genetic syndromes, including Basel-Vanagaite-Smirin-Yosef Syndrome (BVSYS) and Intellectual Disability (ID). This study elucidated the molecular mechanism through which compound heterozygous mutations in the MED25 gene impaired pre-mRNA splicing, ultimately causing BVSYS. Whole exome sequencing (WES) was performed to identify genetic variants, followed by Sanger sequencing for validation. Clinical data were correlated with established MED25-related syndrome phenotypes. Bioinformatics tools were utilized to predict splicing effects and protein structural alterations. Functional characterization involved in vitro minigene splicing assays for the c.1965+1dup mutation and RT-PCR analysis of patient-derived transcripts, while the impact of p.R224G was assessed through protein structure modeling. The proband presented with clinical manifestations such as cognitive impairment, language difficulties, intellectual disability, and microcephaly. The study identified a compound heterozygous mutation in the MED25 gene (NM_030973.4), consisting of c.670C>G (p.R224G) and c.1965+1dup, which was associated with the observed clinical phenotype. Bioinformatics analysis and in vivo/in vitro splicing assays demonstrated that the c.1965+1dup mutation disrupts MED25 pre-mRNA splicing, whereas the c.670C>G (p.R224G) variant does not exhibit this effect. However, bioinformatics analysis suggested that the mutation c.670C>G (p.R224G) may affect gene function by altering the structure of the MED25 protein. These findings demonstrated that two mutation sites identified in the MED25 gene in this case are pathogenic or likely pathogenic and may be associated with the clinical phenotype of the proband in this study.

Basel-Vanagaite-Smirin-Yosef syndrome (BVSYS) is an extremely rare autosomal recessive genetic disorder caused by variants in the MED25 gene. It is characterized by severe developmental delay and variable craniofacial, neurological, ocular, and cardiac anomalies. Since 2015, through whole exome sequencing, 20 patients have been described with common clinical features and biallelic variants in MED25, leading to a better definition of the phenotype associated with BVSYS. We report two young sisters, born to consanguineous parents, presenting with intellectual disability, neurological findings, and dysmorphic features typical of BVSYS, and also with bilateral perisylvian polymicrogyria. The younger sister died at the age of 1 year without autoptic examination. Whole exome sequencing detected a homozygous frameshift variant in the MED25 gene: NM_030973.3:c.1778_1779delAG, p.(Gln593Argfs). This report further delineates the most common clinical features of BVSYS and points to polymicrogyria as a distinctive neuroradiological feature of this syndrome.

Basel-Vanagaite-Smirin-Yosef syndrome is a recently described autosomal recessive intellectual disability syndrome caused by variants in the MED25 gene. While it was originally identified in Brazil, it was further described in Israel by authors who are now the namesake of the condition. A 2018 publication further contributed to its delineation, but the patient's phenotype was complicated by a dual diagnosis. More recently, an article describing a set of affected siblings was published. We describe three, previously unreported, patients showing clinical variability for this newly defined syndrome. The major features determined by "reverse phenotyping" include significant to profound developmental delays/intellectual disability with absent or delayed speech, epilepsy, ocular abnormalities, cleft lip and/or palate, congenital heart disease, urogenital anomalies, skeletal abnormalities, brain malformations and/or microcephaly, failure to thrive, and dysmorphic features. The authors suggest the delineation of an acronym using the gene name and common features seen across the majority of patients reported so far. This new nomination, MED-DOCS, may help clinicians to recognize, suspect, and remember this novel syndrome.

Basel-Vanagaite-Smirin-Yosef syndrome (OMIM 616449) is a rare autosomal recessive genetic disorder characterized by severe developmental delay and variable craniofacial, neurological, cardiac, and ocular anomalies in the presence of variants in the MED25 gene. So far, only a handful of patients have been reported with this condition globally. Here, we report an additional Lebanese family with 2 affected siblings presenting with severely delayed psychomotor and language development as well as craniofacial anomalies. By whole-exome sequencing (WES), a homozygous variant was found in the MED25 gene, c.518T>C, predicted to result in a p.Ile173Thr change in the MED25 protein. This change has recently been reported in another Lebanese family. Review of the literature, the importance of this mutation in the Lebanese population, and the possibility that this condition may be underdiagnosed and only effectively detected using molecular techniques such as WES are discussed.