<b><i>Background:</i></b> Intellectual disability (ID) has been defined as a considerably reduced ability to understand new or complex information and to learn new skills. It is associated with life-long intellectual and adaptive functioning impairments that have a profound impact on individuals, families, and society. It affects about 3% of the general population. ID often comes out with other mental conditions like attention deficit, hyperactivity, and autism spectrum disorders (ASD), and it can be part of a malformation syndrome that affects other organs. It may be syndromic (S-ID) or non-syndromic (NS-ID). <b><i>Objective:</i></b> The aims of this study were to identify the profile of intellectually disable patients being referred for cytogenetic analysis in Morocco, to determine the prevalence of chromosomal abnormalities in a Moroccan group, and to compare the results with those of analogous studies from other countries. <b><i>Participants:</i></b> We included data from Moroccan patients with NS-ID and others with S-ID (mostly Down syndrome cases) who have been referred between 1996 and 2016. 1,626 patients were involved in this study, 1,200 were referred with a clinical diagnosis of Down syndrome, 37 were clinically diagnosed for ASD with ID, and 389 were suspected of NS-ID. <b><i>Results:</i></b> We identified 1,200 cases of Down syndrome. In 1,096 analyses (91.3%), a cytogenetic variant of trisomy 21 was identified: standard trisomy 21 in 1,037 cases (94.6%), a translocation in 34 cases (3.10%), and mosaicism in 25 cases (2.3%). The cytogenetic analysis among ASD with ID cases did not reveal any specific chromosomal abnormalities. The present study also shows that chromosomal abnormalities were present in 6.43% of the patients with NS-ID (25 abnormal karyotypes out of 389 NS-ID cases). Autosomal structural abnormalities were the largest proportion of chromosomal aberrations. <b><i>Conclusion:</i></b> The high rate of chromosomal abnormalities found in the Moroccan patients studied demonstrates the capital importance of cytogenetic evaluation in patients who show ID or any clinical development abnormality.

Early Infantile Epileptic Encephalopathy (known as Ohtahara Syndrome) is one of the most severe and earliest forms of epilepsy, characterized by early seizures onset. It affects newborns and children between two and six years old. Among the genes that have been associated with early infantile epileptic encephalopathy, the STXBP1 gene, which encodes the Syntaxin binding protein1a that is involved in SNARE complex formation, contributes to synaptic vesicles exocytosis. The aim of this study was to identify the most pathogenic polymorphisms of STXBP1 gene and determine their impact on the structure and stability of Stxbp1 protein. The high-risk nonsynonymous single nucleotide polymorphisms (nsSNPs) in the STXBP1 gene were predicted using 13 bioinformatics tools. The conservation analysis was realized by CONSURF web server. The analysis of the impact of the pathogenic SNPs on the structure of Stxbp1 protein was realized using YASARA software, and the molecular dynamics simulation was performed using GROMACS software. Out of 245 nsSNPs, we identified 11 (S42P, H103D R190W, R235G, D238E, L256P, P335S, C354Y, L365V, R406C, and G544D) as deleterious using in silico prediction tools. Conservation analysis results revealed that all these nsSNPs were located in conserved regions. The comparison of the hydrogen and hydrophobic interactions in the wild type Stxbp1 structure and its mutant forms showed that all these nsSNPs affect the protein structure on different levels. The molecular dynamics simulations revealed that the total of nsSNPs affect the protein stability, residual fluctuation, and the compaction at different levels. This study provides helpful information on high risk nsSNPs that may affect the Stxbp1 protein structure and function. Thus, these variants should be taken into consideration during the genetic screening of patients suffering from early infantile epileptic encephalopathy.

The aim of the present study was to determine the frequency and nature of chromosomal abnormalities involved in patients with the clinical spectrum of ambiguous genitalia (AG), amenorrhea, and Turner phenotype, in order to compare them with those reported elsewhere. The study was conducted in the Cytogenetic Department of Pasteur Institute of Morocco, and it reports on the patients who were recruited between 1996 and 2016. Cytogenetic analysis was performed according to the standard method. Among 1,415 patients, chromosomal abnormalities were identified in 7.13% (48/673) of patients with AG, 17.39% (28/161) of patients with primary amenorrhea (PA), 4% (1/25) of patients with secondary amenorrhea, and 23.20% (129/556) of patients with Turner phenotype. However, Turner syndrome was diagnosed in 0.89% (6/673) of patients with AG, 10.56% (17/161) of patients with PA, and 19.78% (110/556) of patients with Turner phenotype. In addition, Klinefelter syndrome and mixed gonadal dysgenesis were confirmed in 2.97% and 1.93% of patients, respectively, with AG, while, chimerism, trisomy 8, and trisomy 13 were confirmed only in 0.15% each. Trisomy 21 was confirmed in patients with AG and Turner phenotype (0.15% and 0.36%, respectively). Moreover, 5.60% (9/161) of patients with PA have been diagnosed as having sex reversal. Thus, the frequency of chromosomal abnormalities observed in Moroccan patients with PA is comparable to that reported in Tunisia, Turkey, Iran, and Hong Kong. However, the frequency is significantly less than that identified in India, Malaysia, Italy, and Romania.

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