Novel Splice Site Pathogenic Variant in STXBP1 Gene in a Child with Intellectual Disability, Epilepsy, and Autism Spectrum Disorder: A Case Report.

Introduction: Pathogenic variants in the STXBP1 gene are associated to a large spectrum of severe early onset developmental and epileptic encephalopathies (OMIM #612164). They were also identified in various other neurodevelopmental disorders. This gene encodes for the syntaxin-binding protein 1, a member of the SEC-1 family of membrane-transport proteins that modulate the presynaptic vesicular fusion by interacting with soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs). However, the physiopathology of STXBP1 pathogenic variants is not yet fully understood. Case Presentation: Herein, we report a patient presenting intellectual disability, early onset seizures, and autism. Clinical exome sequencing identified a novel monoallelic splice pathogenic variant STXBP1(NM_001032221.6):c.38-2A>G. Discussion: Splice-site pathogenic variants in the STXBP1 gene are mostly associated with West syndrome, early onset epilepsy and encephalopathy, and Ohtahara syndrome. Our findings extend clinical and molecular spectrum of STXBP1 gene variants by reporting the first splice-site variant associated with autism along with early onset epilepsy and, and intellectual disability in a patient.

Novel variant related to SATB2-associated syndrome.

BACKGROUND: SATB2-associated syndrome (SAS) also known as Glass syndrome is characterized by/intellectual disability and/or developmental delay coupled with absent or limited speech development. Other abnormalities can be noticed including craniofacial anomalies such as palatal and dental anomalies, behavioural problems and dysmorphic features. It is associated with pathogenic monoallelic variants of the SATB2 gene known to play a key role in brain, dental and jaw development. As phenotype could be unspecific and progressive, clinical diagnostic is difficult. Therefore, genetic testing is mandatory to confirm the disease. Herein, we report clinical and molecular data of a 13-year-old girl with psychomotor developmental delay and behavioural problems. METHODS AND RESULTS: Next-generation sequencing detected the novel monoallelic frameshift variant SATB2(NM_001172509.2): c.1135del(p.Gln379Lysfs*34). Currently, this variant is classified as likely pathogenic according to the American College of Medical Genetics. Sanger sequencing was used to validate the presence of the detected variant in the patient and confirm de novo character of this latter. CONCLUSION: Through this work, we emphasize the value of next-generation sequencing for a precise molecular diagnosis, an adapted clinical management of patients and an adequate genetic counselling of their families.

Molecular diagnosis of Alpha-sarcoglycanopathies by NGS in seven Moroccan families and report of two novel variants.

BACKGROUND: Limb-girdle muscular dystrophies constitute a heterogeneous group of neuromuscular diseases, both clinically and genetically. Limb-girdle muscular dystrophy by alpha-sarcoglycan deficiency or LGMD R3 α-sarcoglycan-related is a subtype of the autosomal recessive sarcoglycanopathies caused by variants in the alpha-sarcoglycan gene (SGCA) at 17q21.33. It appears in childhood by progressive weakness of pelvic and/or scapular girdle muscles and calf hypertrophy, with a wide range of clinical inter- and intra-familial clinical variability. AIMS: Our report extends the molecular spectrum of SGCA gene with the identification of variant disease causing and will help for better management of patients and genetic counseling of families. METHODS: In our study, seven unrelated families presented a clinical and paraclinical picture consistent with alpha-sarcoglycanopathy. A molecular study using Next-Generation Sequencing (NGS) was carried out on them. RESULTS: Six different homozygous variants of the SGCA gene were identified in the patients analyzed, including four previously reported variants and two novel variants predicted to be deleterious by the prediction tools. CONCLUSIONS: Our results expand the spectrum of variants in Moroccan patients with sarcoglycanopathy, specifically LGMDR3, most importantly as this form is not common in the Moroccan population.

A series of four patients with Sotos syndrome harboring novel NSD1 mutations: clinical and molecular description.

BACKGROUND: Sotos syndrome is a rare and complex genetic disorder caused by haploinsufficiency of the NSD1 gene. This syndrome is characterized by rapid early childhood growth, distinct facial features, a learning disability, and multiple other developmental and behavioral challenges. METHODS AND RESULTS: In this work, we describe four Moroccan patients with variable clinical presentations of Sotos syndrome, in whom we identified four novel NSD1 monoallelic pathogenic variants by conducting targeted Next Generation Sequencing. Genetic testing allowed us to provide a precise medical diagnosis to our patients and tailor interventions to each patient's needs. CONCLUSIONS: Being the first work describing a series of Moroccan patients with this syndrome, this case series contributes to the growing body of literature on Sotos syndrome and provides valuable insights into the clinical and molecular characteristics of this rare disorder.

Clinical Exome Sequencing Reveals Novel Mutations in SPTB Gene Associated with Hereditary Spherocytosis in Patients with Suspected Congenital Hemolytic Anemia.

Congenital hemolytic anemia (CHA) is defined as the premature destruction of red blood cells (RBC) due to congenital or acquired defects. The hereditary form of hemolytic anemia can be divided into hemoglobinopathies, membranopathies, and enzymopathies. Hereditary spherocytosis (HS) is the most common inherited RBC membranopathy leading to congenital hemolytic anemia. To date; five genes have been associated with HS coding for cytoskeleton and transmembrane proteins, those genes are SPTB, SLC4A1, EPB42, ANK1, and SPTA1. Due to genetic heterogeneity, clinical exome sequencing (CES) was performed on four unrelated Moroccan patients referred for CHA investigation. Sanger sequencing and qPCR were performed to confirm CES results and to study the de novo character of identified variants. The molecular analysis revealed 3 novel mutations and one previously reported pathogenic variant of the SPTB gene confirming the diagnosis of HS in the four patients. Hereditary spherocytosis anemia is a genetically heterogenous disease which could be misdiagnosed clinically. The introduction of novel sequencing technologies can facilitate accurate genetic diagnosis, allowing an adapted care of the patient and his family.

Currarino Syndrome in Two Moroccan Siblings with Inherited 7q36 Deletion due to Maternal t(7;21)(q36;p11)mat: A Case Report.

Introduction: Currarino syndrome is a rare syndrome with multiple congenital anomalies including sacral agenesis, anorectal malformation, and presence of a presacral mass. Currarino syndrome is considered to be an autosomal dominant inherited disorder, with low penetrance and variable expressivity, but sporadic cases have also been reported. Mutations in MNX1 gene, mapped to 7q36, are the main causes of this syndrome. To the best of our knowledge, less than 400 cases of this syndrome have been mentioned in the literature. Currarino syndrome is often seen in children and considered to be rare in adults; it is mostly found as incidental finding and suspected to be underdiagnosed. Case Presentation: Recognizing the rarity of this syndrome, we present here two siblings with incomplete form of Currarino syndrome combined with microcephaly and intellectual disability. Banding and molecular cytogenetics were used to characterize the origin of this disorder. Banding cytogenetics together with molecular cytogenetics revealed an unbalanced translocation t(7;21)(q36.2;p11.3)mat, leading to a deletion of the 7q36 region in both affected children. Conclusion: This report highlights the importance of cytogenetics in diagnosis of rare genetic syndromes, with impact on genetic counseling of patients and their families. To the best of our knowledge, this is the first Moroccan Currarino syndrome case due to an unbalanced translocation leading to a der(7)t(7;21)(q36.2;p11.3). Also, this is the first Currarino syndrome case associated with a deletion in 7q36 to be reported in Morocco.

A maternally derived complex small supernumerary marker chromosome involving chromosomes 8 and 14: case report and review of the literature.

Introduction: The majority of small supernumerary marker chromosomes (sSMCs) are derived from one single chromosome. Complex sSMCs, on the other hand, consist of genetic material derived from more than one, normally two chromosomes. Complex sSMCs involving chromosomes 8 and 14 are rarely encountered. Case presentation: We present here a 14-month-old boy born from an unrelated couple. At birth, the baby was hypotonic and had a cleft lip and palate, as well as ocular involvement. Throughout the course of development, the baby experienced feeding difficulties, stunted growth, and delayed psychomotor development. Banding together with molecular cytogenetics revealed a balanced maternal translocation t(8;14)(p22.3;q21)mat, leading due to meiotic 3:1 segregation to a partial trisomy of chromosomes 8 and 14 in the affected boy. Discussion/Conclusion: This report highlights the importance of cytogenetics in diagnosis of rare genetic disorders, with impact on genetic counselling of patients and their families. There are three comparable cases in the literature involving both chromosomes 8 and 14, but with different breakpoints; the complex sSMC derived from chromosomes 8 and 14 in this case, characterized as der(14)t(8;14) (p22.3;q21)mat.

High frequency of hotspot mutation in PTPN11 gene among Moroccan patients with Noonan syndrome.

Noonan syndrome (NS; OMIM 163950) is an autosomal dominant RASopathy with variable clinical expression and genetic heterogeneity. Clinical manifestations include characteristic facial features, short stature, and cardiac anomalies. Variants in protein-tyrosine phosphatase, non-receptor-type 11 (PTPN11), encoding SHP-2, account for about half of NS patients, SOS1 in approximately 13%, RAF1 in 10%, and RIT1 each in 9%. Other genes have been reported to cause NS in less than 5% of cases including SHOC2, RASA2, LZTR1, SPRED2, SOS2, CBL, KRAS, NRAS, MRAS, PRAS, BRAF, PPP1CB, A2ML1, MAP2K1, and CDC42. Several additional genes associated with a Noonan syndrome-like phenotype have been identified. Clinical presentation and variants in patients with Noonan syndrome are this study's objectives. We performed Sanger sequencing of PTPN11 hotspot (exons 3, 8, and 13). We report molecular analysis of 61 patients with NS phenotype belonging to 58 families. We screened for hotspot variants (exons 3, 8, and 13) in PTPN11 gene by Sanger sequencing. Twenty-seven patients were carrying heterozygous pathogenic variants of PTPN11 gene with a similar frequency (41.4%) compared to the literature. Our findings expand the variant spectrum of Moroccan patients with NS phenotype in whom the analysis of hotspot variants showed a high frequency of exons 3 and 8. This screening test allowed us to establish a molecular diagnosis in almost half of the patients with a good benefit-cost ratio, with appropriate management and genetic counseling.

Next generation sequencing identifies a pathogenic mutation of WFS1 gene in a Moroccan family with Wolfram syndrome: a case report.

BACKGROUND: Wolfram syndrome is a rare autosomal recessive neurodegenerative disorder that affects 1/200,000 to 1/1,000,000 children. It is characterized by juvenile onset diabetes, optic nerve atrophy and other systemic manifestations. Symptoms of the disease arise mostly in early childhood with a high mortality rate due to severe neurological complications. Two causative genes have been identifed in this syndrome; the classical form is caused by autosomal recessive mutations of the WFS1 gene, and a smaller portion of patients has mutations in the CIDS2 gene, which are responsible for autosomal recessive Wolfram syndrome 2. CASE PRESENTATION: We report the case of a 28-year-old Moroccan boy born from consanguineous parents referred to the department of medical genetics at the National Institute of Health in Rabat. The diagnosis of Wolfram syndrome was made based on insulin-dependent diabetes, optic nerve atrophy, sensorineural deafness, urological abnormalities and psychiatric illness. To establish the diagnosis at a molecular level, we performed next-generation sequencing in the index patient, which revealed compound heterozygous WFS1 mutations: c.1113G > A (p.Trp371Ter) and c.1223_1224insGGAACCACCTGGAGCCCTATGCCCATTT (p.Phe408fs). This second variant has never been described in patients with Wolfram syndrome. CONCLUSION: The identification of the genetic substrate in our patient confirmed the clinical diagnosis of Wolfram syndrome and allowed us to provide him an appropriate management and genetic counseling to his family.

Novel copy number variation of COLQ gene in a Moroccan patient with congenital myasthenic syndrome: a case report and review of the literature.

BACKGROUND: Congenital myasthenic syndromes (CMSs) are rare genetic diseases due to abnormalities of the neuromuscular junction leading to permanent or transient muscle fatigability and weakness. To date, 32 genes were found to be involved in CMSs with autosomal dominant and/or recessive inheritance patterns. CMS with acetylcholinesterase deficiency, in particular, was determined to be due to biallelic mutations of COLQ gene with early-onset clinical signs. Here, we report clinical features and novel molecular findings of COLQ-related CMS in a Moroccan patient with a review of the literature for this rare form. CASE PRESENTATION: In this study, we report the case of a 28-month-old Moroccan female patient with hypotonia, associated to axial muscle weakness, global motor delay, bilateral ptosis, unilateral partial visual field deficiency with normal ocular motility, and fatigable muscle weakness. Clinical exome sequencing revealed a novel homozygous deletion of exon 13 in COLQ gene, NM_005677.4(COLQ):c.(814+1_815-1)_(954+1_955-1) del p.(Gly272Aspfs*11). This finding was subsequently confirmed by quantitative real-time PCR (qPCR) in the proband and her parents. In silico analysis of protein-protein interaction network by STRING tool revealed that 12 proteins are highly associated to COLQ with an elevated confidence score. Treatment with Salbutamol resulted in clear benefits and recovery. CONCLUSIONS: This clinical observation illustrates the important place of next-generation sequencing in the precise molecular diagnosis of heterogeneous forms of CMS, the appropriate management and targeted treatment, and genetic counseling of families, with a better characterization of the mutational profile of this rare disease in the Moroccan population.

Complex translocation leading to13q interstitial deletion in a Moroccan child with retinoblastoma and intellectual disability.

BACKGROUND: Retinoblastoma (RB) is the most common malignant intraocular tumor in children; it affects their eyes often even prenatally. RB may be sporadic or familial, due to germinal mutation in RB1 gene or by abnormal chromosomal abnormalities involving RB1 gene, located in 13q14. Monosomy of subband 13q14 as a partial deletion can also be responsible for RB with additional symptoms. The latter may be RB associated with psychomotor retardation, macrocephaly, broad forehead, thick earlobes, and bulbous nose. MATERIALS AND METHODS: We present here the case of a boy from a consanguineous marriage with bilateral retinoblastoma, intellectual disability and facial dysmorphic features. Classical and molecular cytogenetics were used to recognize genotype-phenotype association. RESULTS: The karyotype showed a three way translocation involving chromosomes 5, 12 and 13. Further molecular cytogenetics analysis revealed a deletion of 13q14 involving the tumor suppressor gene RB1. CONCLUSION: This case highlights the impact of classical and molecular cytogenetics in diagnosis of rare genetic syndromes and for the genetic counselling of patients and their families. Pure molecular karyotyping analyses would miss the underlying chromosomal mechanism leading to the rearrangement.

Mutational spectrum of BRCA1/2 genes in Moroccan patients with hereditary breast and/or ovarian cancer, and review of BRCA mutations in the MENA region.

PURPOSE: Breast cancer (BC) is the most common form of female cancer around the world. BC is mostly sporadic, and rarely hereditary. These hereditary forms are mostly BRCA1- and BRCA2-associated hereditary breast and ovarian cancer syndrome. BRCA1 and BRCA2 genes are large and had some recurrent mutations specific to some populations. Through this work we analyze the most recurrent mutations in Moroccan population and compared them to a large review of other BRCA1/2 spectrum mutations in the MENA region. METHODS: We report in this work a series of 163 unrelated patients (the largest series of Moroccan patients) with familial breast and/or ovarian cancer, selected among patients referred to our oncogenetic outpatient clinic, from 2006 to 2021. To identify genetic variants in these two genes, different genetic analysis strategies have been carried out, using Sanger Sequencing DNA or Target Panel Sequencing. RESULTS: Pathogenic variants were identified in 27.6% of patients. The most frequent mutation identified in our patients was the c.1310_1313delAAGA, BRCA2 (33%), and three other mutations seem more frequent in the Moroccan population (33%) of all reported patients: c.798_799delTT, BRCA1; and c.3279delC, BRCA1; and c.7234_7235insG in BRCA2 gene. CONCLUSION: Through this work, we emphasize the importance of screening for BRCA1 and BRCA2 recurrent mutations in Moroccan patients. Other MENA (MENA: English-language acronym referring to the Middle East and North Africa region) countries had also some recurrent BRCA mutations, which will allow a fast and unexpensive first line genetic analysis and a precise molecular diagnosis. This will allow an adapted follow-up of the patients and a pre-symptomatic diagnosis of their relatives.

Investigation of bacterial diversity using 16S rRNA sequencing and prediction of its functionalities in Moroccan phosphate mine ecosystem.

Native plants in extreme environments may harbor some unique microbial communities with particular functions to sustain their growth and tolerance to harsh conditions. The aim of this study was to investigate the bacterial communities profiles in some native plants and samples of the Moroccan phosphate mine ecosystem by assessing the percentages of taxonomic identification using six hypervariable regions of the 16S rRNA. The rhizosphere of the three wild plants in the Moroccan phosphate mine is characterized by interesting bacterial diversity including Proteobacteria (62.24%, 71.15% and 65.61%), Actinobacteria (22.53%, 15.24%, 22.30%), Bacteroidetes (7.57%; 4.23%; 7.63%), and Firmicutes (5.82%; 1.17%; 2.83%). The bulk phosphate mine samples were dominated by Actinobacteria with average relative abundance of 97.73% that are different from those inferred in the rhizosphere samples of the native plants. The regions V3, V4 and V67 performed better in the taxonomic profiling at different taxonomic levels. Results indicated that both plant genotype and mainly soil conditions may be involved in the shaping of bacterial diversity. Such indication was also confirmed by the prediction of functional profiles that showed enrichment of many functions related to biological nitrogen fixation in the rhizosphere of native plants and the stress related functions in the bulk phosphate mine in comparison with the wheat rhizosphere samples.

Clinical description and mutational profile of a Moroccan series of patients with Rubinstein Taybi syndrome.

BACKGROUND: Rubinstein-Taybi syndrome (RSTS; OMIM 180849) is a rare autosomal dominant developmental disorder with an estimated prevalence of one case per 125,000 live births. RSTS is characterized by typical face, broad thumbs and halluces, short stature, and intellectual disability. Facial dysmorphy is characteristic with microcephaly, low frontal hairline, arched eyebrows, long eyelashes, convex profile of nose, narrow palate, and micrognathia. RSTS is mainly due to mutations or microdeletions of the CREBBP gene (about 60%) and more rarely of the EP300 gene (8%). OBJECTIVE: Clinical description and identification of mutations of patients with Rubinstein Taybi syndrome. METHODS: PCR and direct sequencing of CREBBP gene. RESULTS: We report here, the clinical and molecular data of a series of six Moroccan patients with a phenotype of RSTS. The molecular study of the major gene CREBBP (by Sanger Sequencing followed by CGH array, if sequence normal) revealed point mutations in five patients. For the sixth patient, CGH array revealed a microdeletion carrying the CREBBP gene. Through this work, we emphasize the importance of clinical expertise in the diagnosis, management and genetic counseling in Rubinstein Taybi syndrome.

15q26 deletion in a patient with congenital heart defect, growth restriction and intellectual disability: case report and literature review.

BACKGROUND: 15q26 deletion is a relatively rare chromosomal disorder, and it is described only in few cases. Patients with this aberration show many signs and symptoms, particularly pre- and postnatal growth restriction, developmental delay, microcephaly, intellectual disability and various congenital malformations. CASE PRESENTATION: We report on a girl, 4 years old, of consanguineous parents, with a 15q26 deletion. Clinical manifestations included failure to thrive, developmental delay, microcephaly, dysmorphic facies with broad forehead, hypertelorism, narrowed eyelid slits and protruding columella. The patient also showed skeletal abnormalities, especially clinodactyly of the 5th finger, varus equine right foot and left club foot. Additionally, she had teething delay and divergent strabismus. Heart ultrasound displayed two atrial septal defects with left-to-right shunt, enlarging the right cavities. Routine cytogenetic analysis revealed a shortened 15q chromosome. Subsequent array analysis disclosed a terminal 9.15 Mb deletion at subband 15q26.1-q26.3. Four candidate genes associated with 15q26 deletion phenotype were within the deleted region, i.e. IGF1R, NR2F2, CHD2 and MEF2A. CONCLUSION: We report on an additional case of 15q26 monosomy, characterized by array-CGH. Molecular cytogenetic analysis allowed us to identify the exact size of the deletion, and four candidate genes for genotype-phenotype correlation. 15q26 monosomy should be considered when growth retardation is associated with hearing anomalies and congenital heart defect, especially atrioventricular septal defects (AVSDs) and/or aortic arch anomaly (AAA).

Clinical, cytogenetic and molecular findings in nine Moroccan patients with Fanconi anemia.

INTRODUCTION: Fanconi anemia (FA) is a rare inherited hematological disease due to a defect in the DNA repair pathway resulting in congenital abnormalities and high susceptibility to develop cancers. The cytogenetic analysis using alkylating agents is still a reference test to establish the diagnosis. Despite the genetic heterogeneity, the identification of the causal mutation is actually performed especially after the development of next generation sequencing (NGS). METHODS: we report here nine Moroccan patients referred to the department of Medical Genetics for suspicion of FA. We realized a genetic consultation to establish a clinical record with biological data before carrying out the genetic analysis. Karyotyping with mitomycin was performed for all the probands before elaborating molecular study. We used massively parallel sequencing to analyse the three most frequent mutated genes FANCA, FANCC, and FANCG, representing 84% of all genes involved in FA. RESULTS: all the patients showed hematological signs associated with at least one extra-hematological congenital anomaly. The chromosomal breaks were significantly higher for the nine patients, compared to the controls. The molecular diagnosis was confirmed in 8 of the 9 families tested (88.8%) with 4 novel mutations. The next generation based sequencing identified 9 variations: 6 in the FANCA gene (66.6%), 3 in the FANCG gene (33.3%) and no FANCC variation was found. Of those, 7 were homozygous and 2 were compounds heterozygous. CONCLUSION: to the best of our knowledge, this is the first molecular report of Moroccan patients with FA suggesting the predominance of two genes without any recurrent mutation. The molecular analysis of FANCA and FANCG genes should be offered first for all patients in Morocco.

Homozygous nonsense mutation of WNT10B gene in a Moroccan family with split-hand foot malformation identified by exome sequencing: a case report.

Split-hand foot malformation (SHFM) is a clinically heterogeneous congenital limb defect affecting predominantly the central rays of hands and/or feet. The clinical expression varies in severity between patients as well between the limbs in the same individual. SHFM might be non-syndromic with limb-confined manifestations or syndromic with extra-limb manifestations. Isolated SHFM is a rare condition with an incidence of about 1 per 18,000 live born infants and accounts for 8-17 % of all limb malformations. To date, many chromosomal loci and genes have been described as associated with isolated SHFM, i.e., SHFM1 to 6. SHFM6 is one of the rarest forms of SHFM, and is caused by mutations in WNT10B gene. Less than ten pathogenic variants have been described. We have investigated a large consanguineous Moroccan family with three affected members showing feet malformations with or without split hand malformation phenotypes. Using an exome sequencing approach, we identified a homozygous nonsense variant p.Arg115* of WNT10B gene retaining thereby the diagnosis of SHFM6. This homozygous nonsense mutation identified by exome sequencing in a large family of split hand foot malformation highlights the importance of exome sequencing in genetically heterogeneous entities.

Identification of a novel LAMA2 c.2217G > A, p.(Trp739*) mutation in a Moroccan patient with congenital muscular dystrophy: a case report.

BACKGROUND: Merosin-deficient congenital muscular dystrophy type 1A (MDC1A) is a rare autosomal recessive genetic condition caused by deleterious mutations in the LAMA2 gene encoding the laminin-α2 chain. It is the most frequent subtype of congenital muscular dystrophies (CMDs) characterized by total laminin-α2 deficiency with muscle weakness at birth or in the first six months of life. To the best of our knowledge, this study reports the first molecular diagnosis and genetic defect of this heterogeneous form of CMD performed in a Moroccan medical genetic center using next-generation sequencing (NGS). It allows us to expand the mutational spectrum of the LAMA2 gene. CASE PRESENTATION: We report the case of a female Moroccan child with clinical and paraclinical features in favor of a CMD. She has global congenital hypotonia with generalized muscle weakness, psychomotor retardation, increased serum creatine kinase, and normal brain scan at the age of six months. Targeted NGS leads to the identification of a novel homozygous nonsense mutation c.2217G > A, p.(Trp739*) in the exon 16 of LAMA2. Sanger sequencing confirmed this mutation in the affected patient and showed that her parents are heterozygous carriers. CONCLUSIONS: A modern genetic analysis by NGS improves the genetic diagnosis pathway for adequate genetic counseling of affected families more precisely. An accession number from the National Center for Biotechnology Information (NCBI) ClinVar database was retrieved for this novel LAMA2 mutation.

Novel mutation in the TGFBI gene in a Moroccan family with atypical corneal dystrophy: a case report.

BACKGROUND: Corneal dystrophies (CDs) are a heterogeneous group of bilateral, genetically determined, noninflammatory bilateral corneal diseases that are usually limited to the cornea. CD is characterized by a large variability in the age of onset, evolution and visual impact and the accumulation of insoluble deposits at different depths in the cornea. Clinical symptoms revealed bilateral multiple superficial, epithelial, and stromal anterior granular opacities in different stages of severity among three patients of this family. A total of 99 genes are involved in CDs. The aim of this study was to identify pathogenic variants causing atypical corneal dystrophy in a large Moroccan family and to describe the clinical phenotype with severely different stages of evolution. CASE PRESENTATION: In this study, we report a large Moroccan family with CD. Whole-exome sequencing (WES) was performed in the three affected members who shared a phenotype of corneal dystrophy in different stages of severity. Variant validation and familial segregation were performed by Sanger sequencing in affected sisters and mothers and in two unaffected brothers. Whole-exome sequencing showed a novel heterozygous mutation (c.1772C > A; p.Ser591Tyr) in the TGFBI gene. Clinical examinations demonstrated bilaterally multiple superficial, epithelial and stromal anterior granular opacities in different stages of severity among three patients in this family. CONCLUSIONS: This report describes a novel mutation in the TGFBI gene found in three family members affected by different phenotypic aspects. This mutation is associated with Thiel-Behnke corneal dystrophy; therefore, it could be considered a novel phenotype genotype correlation, which will help in genetic counselling for this family.

Application of next generation sequencing in genetic counseling a case of a couple at risk of cystinosis.

BACKGROUND: In Morocco, consanguinity rate is very high; which lead to an increase in the birth prevalence of infants with autosomal recessive disorders. Previously, it was difficult to diagnose rare autosomal recessive diseases. Next Generation Sequencing (NGS) techniques have considerably improved clinical diagnostics. A genetic diagnosis showing biallelic causative mutations is the requirement for targeted carrier testing in parents, prenatal and preimplantation genetic diagnosis in further pregnancies, and also for targeted premarital testing in future couples at risk of producing affected children by a known autosomal recessive disease. METHODS: In this report, we present our strategy to advise a future couple of first cousins, whose descendants would risk cystinosis; an autosomal recessive lysosomal disease caused by mutations in the CTNS gene. Indeed, our future husband's sister is clinically and biochemically diagnosed with cystinosis in early childhood. First, we opted to identify the patient's CTNS gene abnormality by using (NGS), then we searched for heterozygosity in the couple's DNA, which allows us to predict the exact risk of this familial disease in the future couple's offspring. RESULTS: We have shown that the future husband, brother of the patient is heterozygous for the familial mutation. On the other hand, his future wife did not inherit the familial mutation. Therefore, genetic counseling was reassuring for the risk of familial cystinosis in this couple's offspring. CONCLUSIONS: We report in this study, one of the major applications of (NGS), an effective tool to improve clinical diagnosis and to provide the possibility of targeted premarital carrier testing in couples at risk.