Publications by authors named "Amal AlHashem"

66 Publications

Further delineation of SMG9-related heart and brain malformation syndrome.

Am J Med Genet A 2021 Feb 20. Epub 2021 Feb 20.

Department of Translational Genomics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.

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http://dx.doi.org/10.1002/ajmg.a.62139DOI Listing
February 2021

Exploiting the Autozygome to Support Previously Published Mendelian Gene-Disease Associations: An Update.

Front Genet 2020 31;11:580484. Epub 2020 Dec 31.

Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.

There is a growing interest in standardizing gene-disease associations for the purpose of facilitating the proper classification of variants in the context of Mendelian diseases. One key line of evidence is the independent observation of pathogenic variants in unrelated individuals with similar phenotypes. Here, we expand on our previous effort to exploit the power of autozygosity to produce homozygous pathogenic variants that are otherwise very difficult to encounter in the homozygous state due to their rarity. The identification of such variants in genes with only tentative associations to Mendelian diseases can add to the existing evidence when observed in the context of compatible phenotypes. In this study, we report 20 homozygous variants in 18 genes (, and ) that satisfy the ACMG classification for pathogenic/likely pathogenic if the involved genes had confirmed rather than tentative links to diseases. These variants were selected because they were truncating, founder with compelling segregation or supported by robust functional assays as with the variant that we present its validation using yeast model. Our findings support the previously reported disease associations for these genes and represent a step toward their confirmation.
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http://dx.doi.org/10.3389/fgene.2020.580484DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7806527PMC
December 2020

Proteus syndrome caused by novel somatic AKT1 duplication.

Saudi Med J 2021 Jan;42(1):95-99

Department of Pediatrics, Division of Medical Genetic, Prince Sultan Military Medical City, Riyadh, Kingdom of Saudi Arabia. E-mail.

Proteus syndrome (PS) is a rare overgrowth disorder that presents with asymmetrical growth of the bone and fat tissues following a mosaic pattern mutation. The estimated worldwide incidence is approximately one in one million live births. Proteus syndrome causes disfigurement and psychological impact through its effects on somatic tissue. Due to its rarity and diversity of tissues involved, it represents a significant challenge to caregivers and multidisciplinary medical teams. Here, we report a Saudi girl, with a large left cervical mass discovered antenatally. This mass was identified as a growing cystic hygroma, and she had features of overgrowth and hemangiomas. Whole exome sequencing was negative from the blood lymphocytes and affected tissue sample.  However, deletion duplication analysis from tissue shows a novel mosaic somatic mutation of the AKT1 gene. Somatic mutation remains an obstacle, and the geneticist has an essential role in its management, providing an established genetic diagnosis, prognosis, and family counselling.
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http://dx.doi.org/10.15537/smj.2021.1.25618DOI Listing
January 2021

Neuroimaging manifestations and genetic heterogeneity of Walker-Warburg syndrome in Saudi patients.

Brain Dev 2021 Mar 13;43(3):380-388. Epub 2020 Nov 13.

Neuroradiology Section, Department of Radiology, Prince Sultan Military Medical City, Riyadh, Saudi Arabia. Electronic address:

Background: Walker-Warburg syndrome (WWS), an autosomal recessive disease, is the most severe phenotype of congenital muscular dystrophies. Its diagnosis remains primarily clinical and radiological. Identification of its causative variants will assist genetic counseling. We aim to describe genetic and neuroimaging findings of WWS and investigate the correlation between them.

Methods: We retrospectively reviewed the clinical, genetic and neuroimaging findings of eleven Saudi neonates diagnosed with WWS between April 2012 and December 2018 in a single tertiary care center. Correlation between neuroimaging and genetic findings was investigated.

Results: All patients had macrocephaly except one who had intrauterine growth restriction. Dysmorphic features were identified in nearly half of the patients. Creatine kinase levels were available in nine patients and were always elevated. Homozygous pathogenic variants were identified in all patients spanning POMT1 (n = 5), TMEM5 (n = 3), ISPD (n = 2) and POMT2 (n = 1) including one patient who had a dual molecular diagnosis of ISPD and PGAP2. On neuroimaging, all patients showed cobblestone cortex, classical infratentorial findings, and hydrocephalus. Other cerebral cortical malformations included subependymal heterotopia, polymicrogyria and open-lip schizencephaly in four, two and one patients, respectively. Buphthalmos and microphthalmia were the most prevalent orbital findings and found in all patients either unilaterally or bilaterally.

Conclusion: WWS is a genetically heterogeneous disorder among Saudis. The case with an additional PGAP2-related phenotype exemplifies the increased risk of dual autosomal recessive disorders in consanguineous populations. MRI is excellent in demonstrating spectrum of WWS brain and orbital malformations; however, no definite correlation could be found between the MRI findings and the genetic variant.
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http://dx.doi.org/10.1016/j.braindev.2020.10.012DOI Listing
March 2021

Epilepsy, neuropsychiatric phenotypes, neuroimaging findings, and genotype-neurophenotype correlation in 22q11.2 deletion syndrome.

Neurosciences (Riyadh) 2020 Aug;25(4):287-291

Division of Pediatric Neurology, Department of Pediatrics, Prince Sultan Military Medical City, Riyadh, Kingdom of Saudi Arabia.

Objective: To describe the epilepsy, neuropsychiatric manifestations, and neuroimaging findings in a group of patients with 22q11.2 DS, and to correlate the size of the deleted genetic material with the severity of the phenotype.

Methods: We retrospectively analyzed the medical records of 28 patients (21 pediatric patients and 7 adults) with a genetically confirmed diagnosis of 22q11.2 DS. Clinical data (epilepsy, neurological exam, neuropsychological and developmental assessment, and psychiatric disorders), neuroimaging, and cytogenetic tests were analyzed RESULTS: Of the 28 patients with 22q11.2 DS, 6 (21.4%) had epileptic seizures, 2 had symptomatic hypocalcemic seizures, 4 (14.2%) had a psychiatric disorder, which comprised of attention deficit hyperactivity disorder, autism spectrum disorder, psychosis, and mood disorder, and 17 (60.7%) had developmental delay. All patients with epilepsy had a developmental delay. Twelve patients underwent a neuropsychology assessment. Intellectual levels ranged from moderate intellectual disability (7/12, 58%) to average (5/12, 41.6%). Of the 16 patients, 6 (37.5%) had a normal brain, while 10 (62.5%) had abnormal neuroimaging findings. No significant correlation was found between the size of the deleted genetic material and the severity of the phenotype.

Conclusion: 22q11.2DS patients are at high risk to develop epilepsy, neuropsychiatric manifestations, and structural brain abnormalities. This indicates that this defined genetic locus is crucial for the development of the nervous system, and patients with 22q11.2 DS have genetic susceptibility to develop epilepsy.
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http://dx.doi.org/10.17712/nsj.2020.4.20200045DOI Listing
August 2020

Survey of disorders of sex development in a large cohort of patients with diverse Mendelian phenotypes.

Am J Med Genet A 2020 Sep 19. Epub 2020 Sep 19.

Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.

Disorders of sex development (DSD) are congenital conditions with atypical development of chromosomal, gonadal, or anatomical sex. The estimated incidence ranges from 1 in 4,500-5,500 for strictly defined "ambiguous genitalia" to 1 in 300 or higher when a broader definition is implemented. In this study, we aim to define DSD phenotypes encountered in a large heterogeneous cohort of molecularly characterized Mendelian disorders in a single center. Data were retrieved for patients with documented abnormal genitalia based on the 2006 consensus criteria. Out of 149 patients (129 families) with compatible human phenotype ontology, 76 patients (68 families) had an identified genetic cause and were included in our analysis. Potentially causal variants were identified in 42 genes, and two patients had a dual molecular diagnosis. Six genes have no associated phenotype in OMIM (PIANP, CELSR2, USP2, FAM179B, TXNDC15, and CCDC96). Thirteen genes have non-DSD OMIM phenotypes, thus we are expanding their phenotype to include DSD. We also highlight how certain disorders are under-recognized despite their established DSD phenotype in OMIM, especially CTU2-related DREAM-PL syndrome and TSPYL1-related sudden infant death with dysgenesis of the testes syndrome. In conclusion, this study of a large heterogeneous Mendelian cohort expands the list of genes and disorders beyond those classically DSD-linked.
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http://dx.doi.org/10.1002/ajmg.a.61876DOI Listing
September 2020

Categorized Genetic Analysis in Childhood-Onset Cardiomyopathy.

Circ Genom Precis Med 2020 Oct 1;13(5):504-514. Epub 2020 Sep 1.

Heart Failure & Transplant Program, Prince Sultan Cardiac Center (A. Alwadai).

Background: Childhood-onset cardiomyopathy is a heterogeneous group of conditions the cause of which is largely unknown. The influence of consanguinity on the genetics of cardiomyopathy has not been addressed at a large scale.

Methods: To unravel the genetic cause of childhood-onset cardiomyopathy in a consanguineous population, a categorized approach was adopted. Cases with childhood-onset cardiomyopathy were consecutively recruited. Based on the likelihood of founder mutation and on the clinical diagnosis, genetic test was categorized to either (1) targeted genetic test with targeted mutation test, single-gene test, or multigene panel for Noonan syndrome, or (2) untargeted genetic test with whole-exome sequencing or whole-genome sequencing. Several bioinformatics tools were used to filter the variants.

Results: Two-hundred five unrelated probands with various forms of cardiomyopathy were evaluated. The median age of presentation was 10 months. In 30.2% (n=62), targeted genetic test had a yield of 82.7% compared with 33.6% for whole-exome sequencing/whole-genome sequencing (n=143) giving an overall yield of 53.7%. Strikingly, 96.4% of the variants were homozygous, 9% of which were found in 4 dominant genes. Homozygous variants were also detected in 7 novel candidates ().

Conclusions: Our work demonstrates the impact of consanguinity on the genetics of childhood-onset cardiomyopathy, the value of adopting a categorized population-sensitive genetic approach, and the opportunity of uncovering novel genes. Our data suggest that if a founder mutation is not suspected, adopting whole-exome sequencing/whole-genome sequencing as a first-line test should be considered.
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http://dx.doi.org/10.1161/CIRCGEN.120.002969DOI Listing
October 2020

Successful application of genome sequencing in a diagnostic setting: 1007 index cases from a clinically heterogeneous cohort.

Eur J Hum Genet 2021 Jan 28;29(1):141-153. Epub 2020 Aug 28.

CENTOGENE AG, Rostock, Germany.

Despite clear technical superiority of genome sequencing (GS) over other diagnostic methods such as exome sequencing (ES), few studies are available regarding the advantages of its clinical application. We analyzed 1007 consecutive index cases for whom GS was performed in a diagnostic setting over a 2-year period. We reported pathogenic and likely pathogenic (P/LP) variants that explain the patients' phenotype in 212 of the 1007 cases (21.1%). In 245 additional cases (24.3%), a variant of unknown significance (VUS) related to the phenotype was reported. We especially investigated patients which had had ES with no genetic diagnosis (n = 358). For this group, GS diagnostic yield was 14.5% (52 patients with P/LP out of 358). GS should be especially indicated for ES-negative cases since up to 29.6% of them  could benefit from GS testing (14.5% with P/LP, n = 52 and 15.1% with VUS, n = 54). Genetic diagnoses in most of the ES-negative/GS-positive cases were determined by technical superiority of GS, i.e., access to noncoding regions and more uniform coverage. Importantly, we reported 79 noncoding variants, of which, 41 variants were classified as P/LP. Interpretation of noncoding variants remains challenging, and in many cases, complementary methods based on direct enzyme assessment, biomarker testing and RNA analysis are needed for variant classification and diagnosis. We present the largest cohort of patients with GS performed in a clinical setting to date. The results of this study should direct the decision for GS as standard second-line, or even first-line stand-alone test.
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http://dx.doi.org/10.1038/s41431-020-00713-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7852664PMC
January 2021

Incidence of newborn screening disorders among 56632 infants in Central Saudi Arabia. A 6-year study.

Saudi Med J 2020 Jul;41(7):703-708

Department of Pediatrics, Prince Sultan Military Medical City, Riyadh, Kingdom of Saudi Arabia. E-mail.

Objectives: To determine the incidence of newborn screening (NBS) disorders and to study the key performance indicators of the program.

Methods: This retrospective single-center study enrolled all infants who underwent NBS from January 2012 to December 2017 at Prince Sultan Military Medical City, Riyadh, Saudi Arabia. We screened 17 NBS disorders. Blood samples were collected 24 hours after birth. If the initial result was positive, a second sample was collected. True positive cases were immediately referred for medical management. Data were extracted from laboratory computerized and non-computerized records using case report forms.

Results: During the study period, 56632 infants underwent NBS with a coverage rate of 100%. Thirty-eight cases were confirmed. The incidence of congenital hypothyroidism was 1:3775. The positive predictive value for the detection of congenital hypothyroidism was 11.8%. Propionic aciduria was the most common metabolic disorder, with an incidence of 1:14158. Very long-chain acyl CoA dehydrogenase deficiency and glutaric aciduria type 1 had an incidence of 1:18877 each. Phenylketonuria, biotinidase deficiency, maple syrup urine disease, and citrullinemia had an incidence of 1:28316 each. However, galactosemia and 3-methyl crotonyl carboxylase deficiency had the lowest incidence of 1:56632.

Conclusion: The NBS coverage rate at our facility was 100%. Congenital hypothyroidism was the most frequently detected disorder with an incidence that matches worldwide figures. The incidence of other inherited disorders was consistent with regional figures.
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http://dx.doi.org/10.15537/smj.2020.7.25147DOI Listing
July 2020

Analysis of transcript-deleterious variants in Mendelian disorders: implications for RNA-based diagnostics.

Genome Biol 2020 06 17;21(1):145. Epub 2020 Jun 17.

Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.

Background: At least 50% of patients with suspected Mendelian disorders remain undiagnosed after whole-exome sequencing (WES), and the extent to which non-coding variants that are not captured by WES contribute to this fraction is unclear. Whole transcriptome sequencing is a promising supplement to WES, although empirical data on the contribution of RNA analysis to the diagnosis of Mendelian diseases on a large scale are scarce.

Results: Here, we describe our experience with transcript-deleterious variants (TDVs) based on a cohort of 5647 families with suspected Mendelian diseases. We first interrogate all families for which the respective Mendelian phenotype could be mapped to a single locus to obtain an unbiased estimate of the contribution of TDVs at 18.9%. We examine the entire cohort and find that TDVs account for 15% of all "solved" cases. We compare the results of RT-PCR to in silico prediction. Definitive results from RT-PCR are obtained from blood-derived RNA for the overwhelming majority of variants (84.1%), and only a small minority (2.6%) fail analysis on all available RNA sources (blood-, skin fibroblast-, and urine renal epithelial cells-derived), which has important implications for the clinical application of RNA-seq. We also show that RNA analysis can establish the diagnosis in 13.5% of 155 patients who had received "negative" clinical WES reports. Finally, our data suggest a role for TDVs in modulating penetrance even in otherwise highly penetrant Mendelian disorders.

Conclusions: Our results provide much needed empirical data for the impending implementation of diagnostic RNA-seq in conjunction with genome sequencing.
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http://dx.doi.org/10.1186/s13059-020-02053-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7298854PMC
June 2020

Molecular and clinical characteristics of very-long-chain acyl-CoA dehydrogenase deficiency: A single-center experience in Saudi Arabia.

Saudi Med J 2020 Jun;41(6):590-596

Department of Pediatrics, Prince Sultan Military Medical City, Riyadh, Kingdom of Saudi Arabia. E-mail.

Objectives: To describe the clinical and molecular characteristics of patients with very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency.   Methods: A retrospective observational cross-sectional analysis was conducted on all patients with VLCAD deficiency at  (Genetic/Metabolic Section), Prince Sultan Military Medical City (PSMMC), Riyadh, Saudi Arabia from 2000 to 2019. Demographic, clinical, and laboratory data were abstracted from the electronic hospital records using a case report form. Results: A total of 14 children were analyzed. Six presented with hypoglycemia, 4 with cardiomyopathy, and 10 had rhabdomyolysis. Five patients had early onset severe phenotype, while 9 had mild form. The molecular study revealed homozygous mutations in ACADVL in all 14 patients. Three variants were not reported before. All patients were treated with medium-chain triglyceride and carnitine. Ten patients are alive and have normal development, while 4 died. Conclusion: Most of the patients in this cohort presented in the neonatal period either by newborn screening or clinically with hypoglycemia, cardiomyopathy, and rhabdomyolysis. The new molecular variants detected in this study broaden the genetic spectrum of VLCAD deficiency in Saudi Arabia.
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http://dx.doi.org/10.15537/smj.2020.6.25131DOI Listing
June 2020

An exome-first approach to aid in the diagnosis of primary ciliary dyskinesia.

Hum Genet 2020 Oct 4;139(10):1273-1283. Epub 2020 May 4.

Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.

Unlike disorders of primary cilium, primary ciliary dyskinesia (PCD) has a much narrower clinical spectrum consistent with the limited tissue distribution of motile cilia. Nonetheless, PCD diagnosis can be challenging due to the overlapping features with other disorders and the requirement for sophisticated tests that are only available in specialized centers. We performed exome sequencing on all patients with a clinical suspicion of PCD but for whom no nasal nitric oxide test or ciliary functional assessment could be ordered. Among 81 patients (56 families), in whom PCD was suspected, 68% had pathogenic or likely pathogenic variants in established PCD-related genes that fully explain the phenotype (20 variants in 11 genes). The major clinical presentations were sinopulmonary infections (SPI) (n = 58), neonatal respiratory distress (NRD) (n = 2), laterality defect (LD) (n = 6), and combined LD/SPI (n = 15). Biallelic likely deleterious variants were also encountered in AKNA and GOLGA3, which we propose as novel candidates in a lung phenotype that overlaps clinically with PCD. We also encountered a PCD phenocopy caused by a pathogenic variant in ITCH, and a pathogenic variant in CEP164 causing Bardet-Biedl syndrome and PCD presentation as a very rare example of the dual presentation of these two disorders of the primary and motile cilia. Exome sequencing is a powerful tool that can help "democratize" the diagnosis of PCD, which is currently limited to highly specialized centers.
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http://dx.doi.org/10.1007/s00439-020-02170-2DOI Listing
October 2020

ADAMTS19-associated heart valve defects: Novel genetic variants consolidating a recognizable cardiac phenotype.

Clin Genet 2020 07 19;98(1):56-63. Epub 2020 May 19.

CENTOGENE AG, Rostock, Germany.

Recently, ADAMTS19 was identified as a novel causative gene for autosomal recessive heart valve disease (HVD), affecting mainly the aortic and pulmonary valves. Exome sequencing and data repository (CentoMD) analyses were performed to identify patients with ADAMTS19 variants (two families). A third family was recognized based on cardiac phenotypic similarities and SNP array homozygosity. Three novel loss of function (LoF) variants were identified in six patients from three families. Clinically, all patients presented anomalies of the aortic/pulmonary valves, which included thickening of valve leaflets, stenosis and insufficiency. Three patients had (recurrent) subaortic membrane, suggesting that ADAMTS19 is the first gene identified related to discrete subaortic stenosis. One case presented a bi-commissural pulmonary valve. All patients displayed some degree of atrioventricular valve insufficiency. Other cardiac anomalies included atrial/ventricular septal defects, persistent ductus arteriosus, and mild dilated ascending aorta. Our findings confirm that biallelic LoF variants in ADAMTS19 are causative of a specific and recognizable cardiac phenotype. We recommend considering ADAMTS19 genetic testing in all patients with multiple semilunar valve abnormalities, particularly in the presence of subaortic membrane. ADAMTS19 screening in patients with semilunar valve abnormalities is needed to estimate the frequency of the HVD related phenotype, which might be not so rare.
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http://dx.doi.org/10.1111/cge.13760DOI Listing
July 2020

The morbid genome of ciliopathies: an update.

Genet Med 2020 Jun 14;22(6):1051-1060. Epub 2020 Feb 14.

Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.

Purpose: Ciliopathies are highly heterogeneous clinical disorders of the primary cilium. We aim to characterize a large cohort of ciliopathies phenotypically and molecularly.

Methods: Detailed phenotypic and genomic analysis of patients with ciliopathies, and functional characterization of novel candidate genes.

Results: In this study, we describe 125 families with ciliopathies and show that deleterious variants in previously reported genes, including cryptic splicing variants, account for 87% of cases. Additionally, we further support a number of previously reported candidate genes (BBIP1, MAPKBP1, PDE6D, and WDPCP), and propose nine novel candidate genes (CCDC67, CCDC96, CCDC172, CEP295, FAM166B, LRRC34, TMEM17, TTC6, and TTC23), three of which (LRRC34, TTC6, and TTC23) are supported by functional assays that we performed on available patient-derived fibroblasts. From a phenotypic perspective, we expand the phenomenon of allelism that characterizes ciliopathies by describing novel associations including WDR19-related Stargardt disease and SCLT1- and CEP164-related Bardet-Biedl syndrome.

Conclusion: In this cohort of phenotypically and molecularly characterized ciliopathies, we draw important lessons that inform the clinical management and the diagnostics of this class of disorders as well as their basic biology.
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http://dx.doi.org/10.1038/s41436-020-0761-1DOI Listing
June 2020

Fructose-1,6-bisphosphatase deficiency with confirmed molecular diagnosis. An important cause of hypoglycemia in children.

Saudi Med J 2020 Feb;41(2):199-202

Department of Pediatrics, Medical Genetics and Metabolic Division, Prince Sultan Military Medical City, Riyadh, Kingdom of Saudi Arabia. E-mail.

Objectives: To draw attention towards fructose-1,6-bisphosphatase (FBPase) deficiency as an important cause of hypoglycemia and lactic acidosis and to implement preventive strategies. Methods: This observational, cross-sectional study was conducted on 7 Saudi patients with genetically confirmed FBPase deficiency from 2008 to 2018 at Prince Sultan Military Medical City, Riyadh, Saudi Arabia. Results: Participants ranged in age from 1-10 years, and all presented with recurrent hypoglycemia. All but one had associated severe metabolic acidosis, and 3 patients (42.9%) presented with hypoglycemia and severe acidosis since birth. The mean duration from presentation to diagnosis was 39.4 months, as other diagnoses, like glycogen storage diseases and mitochondrial diseases needed to be ruled out. Development was normal apart from speech delay in one patient with a novel variant of the FBP1 gene. All patients have homozygous variants in the FBP1 gene.  Conclusion: Fructose-1,6-bisphosphatase is an important cause of hypoglycemia and acidosis; therefore, it is important to offer early molecular diagnostics in any child presenting with these symptoms. Molecular diagnostics should always be undertaken to confirm the diagnosis and for further preventive strategies.
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http://dx.doi.org/10.15537/smj.2020.2.24885DOI Listing
February 2020

Intellectual Disability in Two Brothers Caused by De Novo Novel Unbalanced Translocation (13;18) (q34,q23) and De Novo Microdeletion 6q25 Syndrome.

Cureus 2020 Jan 26;12(1):e6778. Epub 2020 Jan 26.

Pediatrics, Princess Nourah Bint Abdulrahman University, Riyadh, SAU.

We report here two brothers with an intellectual disability (ID), dysmorphic features, speech delay, and congenital hypotonia, with chromosomal microarray confirmed. However, two different de novo chromosomal aberrations; unbalanced translocations (13;18) (q34,q23) were found in the elder boys and de novo 6q25 deletion in the second boy. The boy with 13q34 microdeletion and 18q23 microduplication suffered from ID, obesity, dysmorphic features, speech delay, and seizure while the one with 6q25 deletion presented with ID and speech delay. Both parents were tested and were normal. The third child had mild hypotonia at infancy, which improved later. Whole-exome sequencing (WES) showed the three boys carried a likely benign variant in MED12, inherited from the healthy, asymptomatic mother. The father suffered from rheumatoid arthritis and was on chemotherapy during the conception of the first two affected boys. This report places emphasis on the use of a chromosomal microarray in patients with ID, even with familial cases, and reports the paternal use of methotrexate.
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http://dx.doi.org/10.7759/cureus.6778DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6984774PMC
January 2020

Peripheral venous route for administration of ammonul infusion for treatment of acute hyperammonemia. An experience from a tertiary center in Saudi Arabia.

Saudi Med J 2020 Jan;41(1):98-101

Department of Pediatrics, Prince Sultan Military Medical City, Riyadh, Kingdom of Saudi Arabia. E-mail.

Objectives: To determine the local effects of peripheral Ammonul infusion on the skin and the subcutaneous tissues.  Methods: This retrospective study was conducted at Prince Sultan Military Medical City, Riyadh, Saudi Arabia. All children less than 16 years of age admitted between December 2015 and October 2018 with hyperammonemia and received Ammonul infusion for treatment were recruited. Results: Twenty-one patients received the Ammonul infusion. They were admitted 58 times with acute hyperammonemia during the study period, with an average of 2.8 admissions per patient. The mean age of the included patients was 49.5 months. The most frequent underlying diagnoses were propionic acidemia (n=9), urea cycle disorders (n=5), and intrinsic liver disease (n=3). All participants received Ammonul through peripheral lines except 3 who received it through central lines. No extravasation, burns, or other local side effects were observed in this cohort.

Conclusion: This data indicate that the use of Ammonul through a peripheral venous route appears to be safe and not associated with infusion-related local adverse effects.
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http://dx.doi.org/10.15537/smj.2020.1.24760DOI Listing
January 2020

Biallelic Mutations in Tetratricopeptide Repeat Domain 26 (Intraflagellar Transport 56) Cause Severe Biliary Ciliopathy in Humans.

Hepatology 2020 Jun 20;71(6):2067-2079. Epub 2020 Feb 20.

Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.

Background And Aims: The clinical consequences of defective primary cilium (ciliopathies) are characterized by marked phenotypic and genetic heterogeneity. Although fibrocystic liver disease is an established ciliopathy phenotype, severe neonatal cholestasis is rarely recognized as such.

Approach And Results: We describe seven individuals from seven families with syndromic ciliopathy clinical features, including severe neonatal cholestasis (lethal in one and necessitating liver transplant in two). Positional mapping revealed a single critical locus on chromosome 7. Whole-exome sequencing revealed three different homozygous variants in Tetratricopeptide Repeat Domain 26 (TTC26) that fully segregated with the phenotype. TTC26 (intraflagellar transport [IFT] 56/DYF13) is an atypical component of IFT-B complex, and deficiency of its highly conserved orthologs has been consistently shown to cause defective ciliary function in several model organisms. We show that cilia in TTC26-mutated patient cells display variable length and impaired function, as indicated by dysregulated sonic hedgehog signaling, abnormal staining for IFT-B components, and transcriptomic clustering with cells derived from individuals with closely related ciliopathies. We also demonstrate a strong expression of Ttc26 in the embryonic mouse liver in a pattern consistent with its proposed role in the normal development of the intrahepatic biliary system.

Conclusions: In addition to establishing a TTC26-related ciliopathy phenotype in humans, our results highlight the importance of considering ciliopathies in the differential diagnosis of severe neonatal cholestasis even in the absence of more typical features.
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http://dx.doi.org/10.1002/hep.30982DOI Listing
June 2020

Recurrent homozygous damaging mutation in , encoding a protein disulfide isomerase, in four families with microlissencephaly.

J Med Genet 2020 04 5;57(4):274-282. Epub 2019 Oct 5.

Rady Children's Institute for Genomic Medicine, San Diego, California, USA

Background: Protein disulfide isomerase (PDI) proteins are part of the thioredoxin protein superfamily. PDIs are involved in the formation and rearrangement of disulfide bonds between cysteine residues during protein folding in the endoplasmic reticulum and are implicated in stress response pathways.

Methods: Eight children from four consanguineous families residing in distinct geographies within the Middle East and Central Asia were recruited for study. All probands showed structurally similar microcephaly with lissencephaly (microlissencephaly) brain malformations. DNA samples from each family underwent whole exome sequencing, assessment for repeat expansions and confirmatory segregation analysis.

Results: An identical homozygous variant in (c.500G>A), encoding thioredoxin-related transmembrane protein 2, segregated with disease in all four families. This variant changed the last coding base of exon 6, and impacted mRNA stability. All patients presented with microlissencephaly, global developmental delay, intellectual disability and epilepsy. While is an activator of cellular repeat expansion toxicity, patients showed no evidence of repeat expansions.

Conclusion: The c.500G>A allele associates with recessive microlissencephaly, and patients show no evidence of expansions. is the first PDI implicated in a recessive disease, suggesting a protein isomerisation defect in microlissencephaly.
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http://dx.doi.org/10.1136/jmedgenet-2019-106409DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7405652PMC
April 2020

Lessons Learned from Large-Scale, First-Tier Clinical Exome Sequencing in a Highly Consanguineous Population.

Authors:
Dorota Monies Mohammed Abouelhoda Mirna Assoum Nabil Moghrabi Rafiullah Rafiullah Naif Almontashiri Mohammed Alowain Hamad Alzaidan Moeen Alsayed Shazia Subhani Edward Cupler Maha Faden Amal Alhashem Alya Qari Aziza Chedrawi Hisham Aldhalaan Wesam Kurdi Sameena Khan Zuhair Rahbeeni Maha Alotaibi Ewa Goljan Hadeel Elbardisy Mohamed ElKalioby Zeeshan Shah Hibah Alruwaili Amal Jaafar Ranad Albar Asma Akilan Hamsa Tayeb Asma Tahir Mohammed Fawzy Mohammed Nasr Shaza Makki Abdullah Alfaifi Hanna Akleh Suad Yamani Dalal Bubshait Mohammed Mahnashi Talal Basha Afaf Alsagheir Musad Abu Khaled Khalid Alsaleem Maisoon Almugbel Manal Badawi Fahad Bashiri Saeed Bohlega Raashida Sulaiman Ehab Tous Syed Ahmed Talal Algoufi Hamoud Al-Mousa Emadia Alaki Susan Alhumaidi Hadeel Alghamdi Malak Alghamdi Ahmed Sahly Shapar Nahrir Ali Al-Ahmari Hisham Alkuraya Ali Almehaidib Mohammed Abanemai Fahad Alsohaibaini Bandar Alsaud Rand Arnaout Ghada M H Abdel-Salam Hasan Aldhekri Suzan AlKhater Khalid Alqadi Essam Alsabban Turki Alshareef Khalid Awartani Hanaa Banjar Nada Alsahan Ibraheem Abosoudah Abdullah Alashwal Wajeeh Aldekhail Sami Alhajjar Sulaiman Al-Mayouf Abdulaziz Alsemari Walaa Alshuaibi Saeed Altala Abdulhadi Altalhi Salah Baz Muddathir Hamad Tariq Abalkhail Badi Alenazi Alya Alkaff Fahad Almohareb Fuad Al Mutairi Mona Alsaleh Abdullah Alsonbul Somaya Alzelaye Shakir Bahzad Abdulaziz Bin Manee Ola Jarrad Neama Meriki Bassem Albeirouti Amal Alqasmi Mohammed AlBalwi Nawal Makhseed Saeed Hassan Isam Salih Mustafa A Salih Marwan Shaheen Saadeh Sermin Shamsad Shahrukh Shahrukh Hashmi Ayman Shawli Ameen Tajuddin Abdullah Tamim Ahmed Alnahari Ibrahim Ghemlas Maged Hussein Sami Wali Hatem Murad Brian F Meyer Fowzan S Alkuraya

Am J Hum Genet 2019 Oct;105(4):879

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http://dx.doi.org/10.1016/j.ajhg.2019.09.019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6817532PMC
October 2019

A de novo splicing variant supports the candidacy of TLL1 in ASD pathogenesis.

Eur J Hum Genet 2020 04 30;28(4):525-528. Epub 2019 Sep 30.

Department of Pediatrics, Prince Sultan Military Medical City, Riyad, Saudi Arabia.

Congenital heart disease (CHD) is the most common type of birth defects with family- and population-based studies supporting a strong hereditary component. Multifactorial inheritance is the rule although a growing number of Mendelian forms have been described including candidates that have yet to be confirmed independently. TLL1 is one such candidate that was proposed in the etiology of atrial septal defect (ASD). We describe a girl with congenitally corrected transposition of the great arteries (ccTGA) and ASD secundum whose whole-exome sequencing (WES) revealed a de novo splicing (c.1379-2A>G) variant in TLL1 as well as an inherited truncating variant in NODAL. The identification of this dual molecular diagnosis both supports the candidacy of TLL1 in ASD pathogenesis and highlights the power of WES in revealing multilocus cardiac phenotypes.
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http://dx.doi.org/10.1038/s41431-019-0524-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7080731PMC
April 2020

MDH1 deficiency is a metabolic disorder of the malate-aspartate shuttle associated with early onset severe encephalopathy.

Hum Genet 2019 Dec 19;138(11-12):1247-1257. Epub 2019 Sep 19.

Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, 12713, Saudi Arabia.

The reversible oxidation of L-malate to oxaloacetate is catalyzed by NAD(H)-dependent malate dehydrogenase (MDH). MDH plays essential roles in the malate-aspartate shuttle and the tricarboxylic acid cycle. These metabolic processes are important in mitochondrial NADH supply for oxidative phosphorylation. Recently, bi-allelic mutations in mitochondrial MDH2 were identified in patients with global developmental delay, epilepsy and lactic acidosis. We now report two patients from an extended consanguineous family with a deleterious variant in the cytosolic isoenzyme of MDH (MDH1). The homozygous missense variant in the NAD-binding domain of MDH1 led to severely diminished MDH protein expression. The patients presented with global developmental delay, epilepsy and progressive microcephaly. Both patients had normal concentrations of plasma amino acids, acylcarnitines, lactate, and urine organic acids. To identify the metabolic consequences of MDH1 deficiency, untargeted metabolomics was performed on dried blood spots (DBS) from the patients and in MDH1 knockout HEK293 cells that were generated by Crispr/Cas9. Increased levels of glutamate and glycerol-3-phosphate were found in DBS of both patients. In MDH1 KO HEK293 cells, increased levels of glycerol-3-phosphate were also observed, as well as increased levels of aspartate and decreased levels of fumarate. The consistent finding of increased concentrations of glycerol-3-phosphate may represent a compensatory mechanism to enhance cytosolic oxidation of NADH by the glycerol-P-shuttle. In conclusion, MDH1 deficiency is a new metabolic defect in the malate-aspartate shuttle characterized by a severe neurodevelopmental phenotype with elevated concentrations of glycerol-3-phosphate as a potential biomarker.
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http://dx.doi.org/10.1007/s00439-019-02063-zDOI Listing
December 2019

Loss of SMPD4 Causes a Developmental Disorder Characterized by Microcephaly and Congenital Arthrogryposis.

Am J Hum Genet 2019 10 5;105(4):689-705. Epub 2019 Sep 5.

Department of Clinical Genetics, ErasmusMC University Medical Center Rotterdam, Dr. Molewaterplein 40, 3015 GD Rotterdam, the Netherlands. Electronic address:

Sphingomyelinases generate ceramide from sphingomyelin as a second messenger in intracellular signaling pathways involved in cell proliferation, differentiation, or apoptosis. Children from 12 unrelated families presented with microcephaly, simplified gyral pattern of the cortex, hypomyelination, cerebellar hypoplasia, congenital arthrogryposis, and early fetal/postnatal demise. Genomic analysis revealed bi-allelic loss-of-function variants in SMPD4, coding for the neutral sphingomyelinase-3 (nSMase-3/SMPD4). Overexpression of human Myc-tagged SMPD4 showed localization both to the outer nuclear envelope and the ER and additionally revealed interactions with several nuclear pore complex proteins by proteomics analysis. Fibroblasts from affected individuals showed ER cisternae abnormalities, suspected for increased autophagy, and were more susceptible to apoptosis under stress conditions, while treatment with siSMPD4 caused delayed cell cycle progression. Our data show that SMPD4 links homeostasis of membrane sphingolipids to cell fate by regulating the cross-talk between the ER and the outer nuclear envelope, while its loss reveals a pathogenic mechanism in microcephaly.
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http://dx.doi.org/10.1016/j.ajhg.2019.08.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6817560PMC
October 2019

Congenital anomalies and associated risk factors in a Saudi population: a cohort study from pregnancy to age 2 years.

BMJ Open 2019 09 5;9(9):e026351. Epub 2019 Sep 5.

Paediatrics, Prince Sultan Military Medical City, Riyadh, Saudi Arabia.

Objective: To assess the three key issues for congenital anomalies (CAs) prevention and care, namely, CA prevalence, risk factor prevalence and survival, in a longitudinal cohort in Riyadh, Saudi Arabia.

Setting: Tertiary care centre, Riyadh, Saudi Arabia.

Participants: Saudi women enrolled during pregnancy over 3 years and their 28 646 eligible pregnancy outcomes (births, stillbirths and elective terminations of pregnancy for foetal anomalies). The nested case-control study evaluated the CA risk factor profile of the underlying cohort. All CA cases (1179) and unaffected controls (1262) were followed through age 2 years. Referred mothers because of foetal anomaly and mothers who delivered outside the study centre and their pregnancy outcome were excluded.

Primary Outcome Measures: Prevalence and pattern of major CAs, frequency of CA-related risk factors and survival through age 2 years.

Results: The birth prevalence of CAs was 412/10 000 births (95% CI 388.6 to 434.9), driven mainly by congenital heart disease (148 per 10 000) (95% CI 134 to 162), renal malformations (113, 95% CI 110 to 125), neural tube defects (19, 95% CI 25.3 to 38.3) and chromosomal anomalies (27, 95% CI 21 to 33). In this study, the burden of potentially modifiable risk factors included high rates of diabetes (7.3%, OR 1.98, 95% CI 1.04 to 2.12), maternal age >40 years (7.0%, OR 2.1, 95% CI 1.35 to 3.3), consanguinity (54.5%, OR 1.5, 95% CI 1.28 to 1.81). The mortality for live births with CAs at 2 years of age was 15.8%.

Conclusions: This study documented specific opportunities to improve primary prevention and care. Specifically, folic acid fortification (the neural tube defect prevalence was >3 times that theoretically achievable by optimal fortification), preconception diabetes screening and consanguinity-related counselling could have significant and broad health benefits in this cohort and arguably in the larger Saudi population.
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http://dx.doi.org/10.1136/bmjopen-2018-026351DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6731804PMC
September 2019

Genetic, clinical and biochemical characterization of a large cohort of patients with hyaline fibromatosis syndrome.

Orphanet J Rare Dis 2019 08 27;14(1):209. Epub 2019 Aug 27.

Centogene AG, Am Strande 7, 18057, Rostock, Germany.

Background: Hyaline fibromatosis syndrome (HFS) is a rare clinical condition in which bi-allelic variants in ANTXR2 are associated with extracellular hyaline deposits. It manifests as multiple skin nodules, patchy hyperpigmentation, joint contractures and severe pain with movement. HFS shows some clinical overlap to Farber disease (FD), a recessive lysosomal storage disorder.

Results: We here present the largest cohort of independent, genetically confirmed HFS cases reported to date: in 19 unrelated index patients, we identified ten distinct homozygous ANTXR2 mutations, three of which are novel frame-shift variants. The associated clinical data are consistent with the previous hypothesis of non-truncating variants in the terminal exons 13-17 to confer rather mild phenotypes. The novel observation of gender-dependent disease manifestation in our cohort received support from a meta-analysis of all previously published cases. Untargeted blood-based metabolomics revealed patient samples to be biochemically distinct from control samples. Numerous potential HFS biomarker metabolites could thus be identified. We also found metabolomics profiles of HFS patients to highly overlap with those from FD patients.

Conclusions: Our study extends the mutational spectrum for HFS, suggests gender-dependency of manifestation, and provides pilot metabolomics data for biomarker identification and a better pathomechanistic understanding of the disorder.
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http://dx.doi.org/10.1186/s13023-019-1183-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6712857PMC
August 2019

Lessons Learned from Large-Scale, First-Tier Clinical Exome Sequencing in a Highly Consanguineous Population.

Authors:
Dorota Monies Mohammed Abouelhoda Mirna Assoum Nabil Moghrabi Rafiullah Rafiullah Naif Almontashiri Mohammed Alowain Hamad Alzaidan Moeen Alsayed Shazia Subhani Edward Cupler Maha Faden Amal Alhashem Alya Qari Aziza Chedrawi Hisham Aldhalaan Wesam Kurdi Sameena Khan Zuhair Rahbeeni Maha Alotaibi Ewa Goljan Hadeel Elbardisy Mohamed ElKalioby Zeeshan Shah Hibah Alruwaili Amal Jaafar Ranad Albar Asma Akilan Hamsa Tayeb Asma Tahir Mohammed Fawzy Mohammed Nasr Shaza Makki Abdullah Alfaifi Hanna Akleh Suad Yamani Dalal Bubshait Mohammed Mahnashi Talal Basha Afaf Alsagheir Musad Abu Khaled Khalid Alsaleem Maisoon Almugbel Manal Badawi Fahad Bashiri Saeed Bohlega Raashida Sulaiman Ehab Tous Syed Ahmed Talal Algoufi Hamoud Al-Mousa Emadia Alaki Susan Alhumaidi Hadeel Alghamdi Malak Alghamdi Ahmed Sahly Shapar Nahrir Ali Al-Ahmari Hisham Alkuraya Ali Almehaidib Mohammed Abanemai Fahad Alsohaibaini Bandar Alsaud Rand Arnaout Ghada M H Abdel-Salam Hasan Aldhekri Suzan AlKhater Khalid Alqadi Essam Alsabban Turki Alshareef Khalid Awartani Hanaa Banjar Nada Alsahan Ibraheem Abosoudah Abdullah Alashwal Wajeeh Aldekhail Sami Alhajjar Sulaiman Al-Mayouf Abdulaziz Alsemari Walaa Alshuaibi Saeed Altala Abdulhadi Altalhi Salah Baz Muddathir Hamad Tariq Abalkhail Badi Alenazi Alya Alkaff Fahad Almohareb Fuad Al Mutairi Mona Alsaleh Abdullah Alsonbul Somaya Alzelaye Shakir Bahzad Abdulaziz Bin Manee Ola Jarrad Neama Meriki Bassem Albeirouti Amal Alqasmi Mohammed AlBalwi Nawal Makhseed Saeed Hassan Isam Salih Mustafa A Salih Marwan Shaheen Saadeh Sermin Shamsad Shahrukh Shahrukh Hashmi Ayman Shawli Ameen Tajuddin Abdullah Tamim Ahmed Alnahari Ibrahim Ghemlas Maged Hussein Sami Wali Hatem Murad Brian F Meyer Fowzan S Alkuraya

Am J Hum Genet 2019 06 23;104(6):1182-1201. Epub 2019 May 23.

Department of Genetics, King Faisal Specialist Hospital and Research Centre, Riyadh 11211, Saudi Arabia; Saudi Human Genome Program, King Abdulaziz City for Science and Technology, Riyadh 12354, Saudi Arabia; College of Medicine, Alfaisal University, Riyadh 11533, Saudi Arabia. Electronic address:

We report the results of clinical exome sequencing (CES) on >2,200 previously unpublished Saudi families as a first-tier test. The predominance of autosomal-recessive causes allowed us to make several key observations. We highlight 155 genes that we propose to be recessive, disease-related candidates. We report additional mutational events in 64 previously reported candidates (40 recessive), and these events support their candidacy. We report recessive forms of genes that were previously associated only with dominant disorders and that have phenotypes ranging from consistent with to conspicuously distinct from the known dominant phenotypes. We also report homozygous loss-of-function events that can inform the genetics of complex diseases. We were also able to deduce the likely causal variant in most couples who presented after the loss of one or more children, but we lack samples from those children. Although a similar pattern of mostly recessive causes was observed in the prenatal setting, the higher proportion of loss-of-function events in these cases was notable. The allelic series presented by the wealth of recessive variants greatly expanded the phenotypic expression of the respective genes. We also make important observations about dominant disorders; these observations include the pattern of de novo variants, the identification of 74 candidate dominant, disease-related genes, and the potential confirmation of 21 previously reported candidates. Finally, we describe the influence of a predominantly autosomal-recessive landscape on the clinical utility of rapid sequencing (Flash Exome). Our cohort's genotypic and phenotypic data represent a unique resource that can contribute to improved variant interpretation through data sharing.
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http://dx.doi.org/10.1016/j.ajhg.2019.04.011DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6562004PMC
June 2019

Biallelic variants in the transcription factor PAX7 are a new genetic cause of myopathy.

Genet Med 2019 11 16;21(11):2521-2531. Epub 2019 May 16.

CHU Sainte-Justine Research Center, University of Montreal, Montreal, QC, Canada.

Purpose: Skeletal muscle growth and regeneration rely on muscle stem cells, called satellite cells. Specific transcription factors, particularly PAX7, are key regulators of the function of these cells. Knockout of this factor in mice leads to poor postnatal survival; however, the consequences of a lack of PAX7 in humans have not been established.

Methods: Here, we study five individuals with myopathy of variable severity from four unrelated consanguineous couples. Exome sequencing identified pathogenic variants in the PAX7 gene. Clinical examination, laboratory tests, and muscle biopsies were performed to characterize the disease.

Results: The disease was characterized by hypotonia, ptosis, muscular atrophy, scoliosis, and mildly dysmorphic facial features. The disease spectrum ranged from mild to severe and appears to be progressive. Muscle biopsies showed the presence of atrophic fibers and fibroadipose tissue replacement, with the absence of myofiber necrosis. A lack of PAX7 expression was associated with satellite cell pool exhaustion; however, the presence of residual myoblasts together with regenerating myofibers suggest that a population of PAX7-independent myogenic cells partially contributes to muscle regeneration.

Conclusion: These findings show that biallelic variants in the master transcription factor PAX7 cause a new type of myopathy that specifically affects satellite cell survival.
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http://dx.doi.org/10.1038/s41436-019-0532-zDOI Listing
November 2019

6-Pyruvoyltetrahydropterin Synthase Deficiency: Review and Report of 28 Arab Subjects.

Pediatr Neurol 2019 07 18;96:40-47. Epub 2019 Feb 18.

Division of Genetics, Department of Pediatrics, King Abdulaziz Medical City, Ministry of National Guard-Health Affairs (MNGHA), Riyadh, Saudi Arabia; King Abdullah International Medical Research Center (KAIMRC), Riyadh, Saudi Arabia; College of Medicine, King Saud Bin Abdulaziz University for Health Sciences, Riyadh, Saudi Arabia. Electronic address:

Background: Tetrahydrobiopterin is an essential cofactor for the hydroxylation of aromatic amino acids phenylalanine, tyrosine, and tryptophan. Therefore, tetrahydrobiopterin deficiency results in hyperphenylalaninemia as well as dopamine and serotonin depletion in the central nervous system. The enzyme 6-pyruvoyltetrahydropterin synthase catalyzes the second step of de novo synthesis of tetrahydrobiopterin, and its deficiency is the most frequent cause of tetrahydrobiopterin metabolism disorders.

Method: We conducted a retrospective chart review of 28 subjects from 24 families with molecularly confirmed 6-pyruvoyltetrahydropterin synthase deficiency from six centers in three Arab countries. We reviewed clinical, biochemical, and molecular data. We also reviewed previously published cohorts of subjects with 6-pyruvoyltetrahydropterin synthase deficiency.

Results: Similar to previous observations, we show that early treatment (less than two months) is associated with better outcome. We identify eight PTS variants in 24 independent families. The most common variant is (c.238A>G; p.M80V) with an allele count of 33%. We also identify one novel variant (c.2T>G; p.?).

Conclusion: The deficiency of 6-pyruvoyltetrahydropterin synthase is relatively common in the Arab population and should be considered in individuals with hyperphenylalaninemia. More natural history studies with comprehensive biochemical and molecular genetics data are needed for a robust base for the development of future therapy.
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http://dx.doi.org/10.1016/j.pediatrneurol.2019.02.008DOI Listing
July 2019

The many faces of peroxisomal disorders: Lessons from a large Arab cohort.

Clin Genet 2019 02 18;95(2):310-319. Epub 2018 Dec 18.

Department of Genetics, King Faisal Specialist Hospital and Research Center, Riyadh, Saudi Arabia.

Defects in the peroxisomes biogenesis and/or function result in peroxisomal disorders. In this study, we describe the largest Arab cohort to date (72 families) of clinically, biochemically and molecularly characterized patients with peroxisomal disorders. At the molecular level, we identified 43 disease-causing variants, half of which are novel. The founder nature of many of the variants allowed us to calculate the minimum disease burden for these disorders in our population ~1:30 000, which is much higher than previous estimates in other populations. Clinically, we found an interesting trend toward genotype/phenotype correlation in terms of long-term survival. Nearly half (40/75) of our peroxisomal disorders patients had documented survival beyond 1 year of age. Most unusual among the long-term survivors was a multiplex family in which the affected members presented as adults with non-specific intellectual disability and epilepsy. Other unusual presentations included the very recently described peroxisomal fatty acyl-CoA reductase 1 disorder as well as CRD, spastic paraparesis, white matter (CRSPW) syndrome. We conclude that peroxisomal disorders are highly heterogeneous in their clinical presentation. Our data also confirm the demonstration that milder forms of Zellweger spectrum disorders cannot be ruled out by the "gold standard" very long chain fatty acids assay, which highlights the value of a genomics-first approach in these cases.
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http://dx.doi.org/10.1111/cge.13481DOI Listing
February 2019