Genetic Causes In Patients Research Articles

Syndromic ciliopathy: a taiwanese single-center study

BackgroundSyndromic ciliopathies are a group of congenital disorders characterized by broad clinical and genetic overlap, including obesity, visual problems, skeletal anomalies, mental retardation, and renal diseases. The hallmark of the pathophysiology among these disorders is defective ciliary functions or formation. Many different genes have been implicated in the pathogenesis of these diseases, but some patients still remain unclear about their genotypes.MethodsThe aim of this study was to identify the genetic causes in patients with syndromic ciliopathy. Patients suspected of or meeting clinical diagnostic criteria for any type of syndromic ciliopathy were recruited at a single diagnostic medical center in Southern Taiwan. Whole exome sequencing (WES) was employed to identify their genotypes and elucidate the mutation spectrum in Taiwanese patients with syndromic ciliopathy. Clinical information was collected at the time of patient enrollment.ResultsA total of 14 cases were molecularly diagnosed with syndromic ciliopathy. Among these cases, 10 had Bardet-Biedl syndrome (BBS), comprising eight BBS2 patients and two BBS7 patients. Additionally, two cases were diagnosed with Alström syndrome, one with Oral-facial-digital syndrome type 14, and another with Joubert syndrome type 10. A total of 4 novel variants were identified. A recurrent splice site mutation, BBS2: c.534 + 1G > T, was present in all eight BBS2 patients, suggesting a founder effect. One BBS2 patient with homozygous c.534 + 1G > T mutations carried a third ciliopathic allele, TTC21B: c.264_267dupTAGA, a nonsense mutation resulting in a premature stop codon and protein truncation.ConclusionsWhole exome sequencing (WES) assists in identifying molecular pathogenic variants in ciliopathic patients, as well as the genetic hotspot mutations in specific populations. It should be considered as the first-line genetic testing for heterogeneous disorders characterized by the involvement of multiple genes and diverse clinical manifestations.

Identification of COL4A4 variants in Chinese patients with familial hematuria.

Background: Benign familial hematuria and Alport syndrome are common causes of familial hematuria among children and young adults, which are attributable to variants in the collagen type IV alpha chain genes, COL4A3, COL4A4, or COL4A5. The study was conducted to identify the underlying genetic causes in patients with familial hematuria. Methods: Two unrelated Han-Chinese pedigrees with familial hematuria were recruited for this study. Whole exome sequencing was combined with in silico analysis to identify potential genetic variants, followed by variant confirmation by Sanger sequencing. Reverse transcription, PCR, and Sanger sequencing were performed to evaluate the effect of the detected splicing variant on mRNA splicing. Results: A novel heterozygous splicing c.595-1G>A variant and a known heterozygous c.1715G>C variant in the collagen type IV alpha 4 chain gene (COL4A4) were identified and confirmed in patients of pedigree 1 and pedigree 2, respectively. Complementary DNA analysis indicated this splicing variant could abolish the canonical splice acceptor site and cause a single nucleotide deletion of exon 10, which was predicted to produce a truncated protein. Conclusions: The two COL4A4 variants, c.595-1G>A variant and c.1715G>C (p.Gly572Ala) variant, were identified as the genetic etiologies of two families with familial hematuria, respectively. Our study broadened the variant spectrum of the COL4A4 gene and explained the possible pathogenesis, which will benefit clinical management and genetic counseling.

Clinical manifestation of Johanson-Blizzard syndrome in patient with nucleotide variants in UBR1 gene

Introduction. Johanson-Blizzard syndrome (JBS) is a very rare genetic disorder caused by a mutation of the ubiquitin protein ligase E3 component N-recognin 1 (UBR1) gene. Clinical diagnosis is based on the pathognomonic combination of congenital exocrine pancreatic insufficiency and characteristic signs of facial dysmorphology (nasal wing hypoplasia/aplasia and oligodontia of permanent teeth). Diagnosis is confirmed by genetic screening of the UBR1 gene. The aim of this case report was to emphasize that nucleotide variants in the UBR1 gene, described as benign or unclassified, should still be considered a genetic cause of the clinical characteristics in patients with JBS. Case report. We present an 8-month-old child, with clinical features of JBS, who was admitted to our hospital due to poor weight gain and loose stools. Upon admission, signs of protein-energy malnutrition, facial dysmorphology, and other anomalies were observed. The child had hypotonia and convergent strabismus. A laboratory examination confirmed exocrine pancreatic insufficiency and hypothyroidism. Genetic testing confirmed two single nucleotide variants in the UBR1 gene ? chromosome 15q15.2: NM_174916.3:c.4700+12A>G (intron 42) and NM_174916.3 UBR1:c.862-18C>T (intron 07). A pancreatic enzyme replacement therapy with liposoluble vitamin supplementation and adequate nutrition was conducted. Conclusion. Recognizing the clinical features of JBS and confirming it with genetic analysis is essential, especially in patients with idiopathic pancreatic insufficiency. Even when genetic confirmation is not possible, adequate treatment is necessary for normal growth and development of the child.

Clinical exome sequencing identifies novel compound heterozygous mutations of the POMT2 gene in patients with limb-girdle muscular dystrophy.

Mutations in protein O-mannosyltransferase 2 (POMT2) (MIM#607439) have been identified in severe congenital muscular dystrophy such as Walker-Warburg syndrome (WWS) and milder limb-girdle muscular dystrophy type 2N (LGMD2N). The aim of this study is to investigate the genetic causes in patients with LGMD2N. Three patients diagnosed with mild limb-girdle muscular dystrophy were recruited. The genetically pathogenic variant was identified by clinical exome sequencing, and healthy controls were verified by Sanger sequencing. Novel compound heterozygous mutations c.800A > G and c.1074_1075delinsAT of POMT2 were revealed in one affected individual by clinical exome sequencing. There was no report of these two variants and predicted to be highly damaging to the function of the POMT2. The novel variants extend the spectrum of POMT2 mutations, which promotes the prognostic value of testing for POMT2 mutations in patients with LGMD2N.

Identification of nine novel variants across PAX3, SOX10, EDNRB, and MITF genes in Waardenburg syndrome with next-generation sequencing.

Waardenburg syndrome (WS) is a hereditary, genetically heterogeneous disorder characterized by variable presentations of sensorineural hearing impairment and pigmentation anomalies. This study aimed to investigate the clinical features of WS in detail and determine the genetic causes of patients with clinically suspected WS. A total of 24 patients from 21 Han-Taiwanese families were enrolled and underwent comprehensive physical and audiological examinations. We applied targeted next-generation sequencing (NGS) to investigate the potential causative variants in these patients and further validated the candidate variants through Sanger sequencing. We identified 19 causative variants of WS in our cohort. Of these variants, nine were novel and discovered in PAX3, SOX10, EDNRB, and MITF genes, including missense, nonsense, deletion, and splice site variants. Several patients presented with skeletal deformities, hypotonia, megacolon, and neurological disorders that were rarely seen in WS. This study revealed highly phenotypic variability in Taiwanese WS patients and demonstrated that targeted NGS allowed us to clarify the genetic diagnosis and extend the genetic variant spectrum of WS.

Clinical impact of whole-genome sequencing in patients with early-onset dementia

BackgroundIn the clinical setting, identification of the genetic cause in patients with early-onset dementia (EOD) is challenging due to multiple types of genetic tests required to arrive at a diagnosis....

Genetic architecture in neonatal intensive care unit patients with congenital heart defects: a retrospective study from the China Neonatal Genomes Project

BackgroundCongenital heart defects (CHDs) are the most common type of birth defects. The genetic aetiology of CHD is complex and incompletely understood. The overall distribution of genetic causes in patients...

Rare missense variants in Tropomyosin‐4 (TPM4) are associated with platelet dysfunction, cytoskeletal defects, and excessive bleeding

BackgroundA significant challenge is faced for the genetic diagnosis of inherited platelet disorders in which candidate genetic variants can be found in more than 100 bleeding, thrombotic, and platelet disorder genes, especially within families in which there are both normal and low platelet counts. Genetic variants of unknown clinical significance (VUS) are found in a significant proportion of such patients in which functional studies are required to prove pathogenicity. ObjectiveTo identify the genetic cause in patients with a suspected platelet disorder and subsequently perform a detailed functional analysis of the candidate genetic variants found. MethodsGenetic and functional studies were undertaken in three patients in two unrelated families with a suspected platelet disorder and excessive bleeding. A targeted gene panel of previously known bleeding and platelet genes was used to identify plausible genetic variants. Deep platelet phenotyping was performed using platelet spreading analysis, transmission electron microscopy, immunofluorescence, and platelet function testing using lumiaggregometry and flow cytometry. ResultsWe report rare conserved missense variants (p.R182C and p.A183V) in TPM4 encoding tromomyosin‐4 in 3 patients. Deep platelet phenotyping studies revealed similar platelet function defects across the 3 patients including reduced platelet secretion, and aggregation and spreading defects suggesting that TPM4 missense variants impact platelet function and show a disordered pattern of tropomyosin staining. ConclusionsGenetic and functional TPM4 defects are reported making TPM4 a diagnostic grade tier 1 gene and highlights the importance of including TPM4 in diagnostic genetic screening for patients with significant bleeding and undiagnosed platelet disorders, particularly for those with a normal platelet count.

Molecular genetic analysis and growth hormone response in patients with syndromic short stature

BackgroundSyndromic short stature is a genetic and phenotypic heterogeneous disorder with multiple causes. This study aims to identify genetic causes in patients with syndromic short stature of unknown cause and evaluate the efficacy of the growth hormone response.MethodsTrio-whole-exome sequencing was applied to identify pathogenic gene mutations in seven patents with short stature, multiple malformations, and/or intellectual disability. Whole-genome low-coverage sequencing was also performed to identify copy number variants in three patients with concurrent intellectual disability. Recombinant human growth hormone was administered to improve height in patients with an identified cause of syndromic short stature.ResultsOf the seven patients, three pathogenic/likely pathogenic gene mutations, including one FGFR3 mutation (c.1620C>A p.N540K), one novel GNAS mutation (c.2288C>T p.A763V), and one novel TRPS1 mutation (c.2527_c.2528dupTA p.S843fsX72), were identified in three patients. No copy number variants were identified in the three patients with concurrent intellectual disability. The proband with an FGFR3 mutation, a female 4 and 3/12 years of age, was diagnosed with hypochondroplasia. Long-acting growth hormone improved her height from 85.8 cm [− 5.05 standard deviation (SD)] to 100.4 cm (− 4.02 SD), and her increased height SD score (SDS) was 1.03 after 25 months of treatment. The proband with a GNAS mutation, a female 12 and 9/12 years of age, was diagnosed with pseudohypoparathyroidism Ia. After 14 months of treatment with short-acting growth hormone, her height improved from 139.3 cm (− 2.69 SD) to 145.0 cm (− 2.36 SD), and her increased height SDS was 0.33.ConclusionsTrio-whole-exome sequencing was an important approach to confirm genetic disorders in patients with syndromic short stature of unknown etiology. Short-term growth hormone was effective in improving height in patients with hypochondroplasia and pseudohypoparathyroidism Ia.

Clinical and molecular genetic findings of hereditary Parkinson's patients from Turkey

IntroductionThe majority of Parkinson's disease (PD) ensue late-onset with a complex spectrum of environmental and genetic risk factors. Awareness of genetic causes in patients with PD is essential for genetic counseling and future genotype-oriented therapeutic developments. MethodsLarge pathogenic changes in eight PD-related genes and small pathogenic sequence variants in 22 PD-related genes were investigated simultaneously in 82 PD patients from 79 families where clinical evaluations were performed. The phenotypic characteristics of the patients with molecular changes were examined for genotype-phenotype relations. ResultsPathogenic variants in SNCA, PRKN, DJ-1, FBXO7, and GBA genes were determined in 25 patients from 24 families (24/79, 30%). Associated variants were found in PRKN in 14, SNCA in three, FBXO7 in two, and DJ-1 in one patient. A novel homozygous deletion (c.491delT, p.(V164Dfs*13) (SCV001733595)) leading to protein truncation in the PRKN gene was identified in two patients from the same family. Furthermore, heterozygous GBA gene variants were detected in five patients from different families. ConclusionIt has been shown that the most common cause of genetically transmitted PD is the PRKN gene, while LRRK2 does not play an essential role in this selected population. It has been suggested that even if the autosomal recessive inheritance is expected, genes with autosomal dominant effects such as SNCA should not be overlooked and suggested for investigation. Our study is also the first for evaluating the pathogenic GBA variants’ frequency in PD patients from Turkey.

Consanguinity-based analysis of exome sequencing yields likely genetic causes in patients with inherited retinal dystrophy

BackgroundConsanguineous families have a relatively high prevalence of genetic disorders caused by bi-allelic mutations in recessive genes. This study aims to evaluate the effectiveness and efficiency of a consanguinity-based exome sequencing approach to capturing genetic mutations in inherited retinal dystrophy families with consanguineous marriages.MethodsTen unrelated consanguineous families with a proband affected by inherited retinal dystrophy were recruited in this study. All participants underwent comprehensive ophthalmic examinations. Whole exome sequencing was performed, followed by a homozygote-prior strategy to rapidly filter disease-causing mutations. Bioinformatic prediction of pathogenicity, Sanger sequencing and co-segregation analysis were carried out for further validation.ResultsIn ten consanguineous families, a total of 10 homozygous mutations in 8 IRD genes were identified, including 2 novel mutations, c.1654_1655delAG (p. R552Afs*5) in gene FAM161A in a patient diagnosed with retinitis pigmentosa, and c.830T > C (p.L277P) in gene CEP78 in a patient diagnosed with cone and rod dystrophy.ConclusionThe genetic etiology in consanguineous families with IRD were successfully identified using consanguinity-based analysis of exome sequencing data, suggesting that this approach could provide complementary insights into genetic diagnoses in consanguineous families with variant genetic disorders.

New Cohort of Patients With CEDNIK Syndrome Expands the Phenotypic and Genotypic Spectra.

ObjectiveTo report 6 new patients with cerebral dysgenesis, neuropathy, ichthyosis, and keratoderma (CEDNIK) syndrome.MethodsClinical exome or targeted sequencing were performed to elucidate the molecular genetic cause in patients with neurocognitive abnormalities and brain imaging findings.ResultsCEDNIK syndrome is a rare genetic condition caused by biallelic pathogenic loss-of-function variants in synaptosomal-associated protein 29 (SNAP29), which encodes a vesicular membrane fusion protein. Clinical manifestations include significant developmental delay/intellectual disability (DD/ID), brain abnormalities, failure to thrive, and skin abnormalities. To date, 19 patients from 10 unrelated families with CEDNIK syndrome have been reported. We report 5 additional patients with homozygous predicted loss-of-function variants in SNAP29 and one with compound heterozygous variants: a frameshift SNAP29 variant and a 370 kb deletion on 22q11.2. All patients exhibit DD/ID, ichthyosis and/or palmoplantar keratoderma, and hypotonia. Four of 6 subjects had hypomyelinated white matter on MRI, 2 of 6 had early puberty, and 4 of 6 had strabismus, which were previously rarely reported. Other phenotypes were variably present, including dysmorphic features, feeding difficulties, and recurrent respiratory infections. The cohort includes 2 siblings with a c.2T>C variant who have a relatively milder phenotype, a patient with the most C-terminal variant yet described (c.622G>T), and 3 patients with previously described variants (c.354dupG, c.487dupA).ConclusionsThis cohort of 6 additional patients expands the genotypic and phenotypic spectrum of CEDNIK syndrome, highlighting previously under-recognized features such as hypomyelination, seizures, and early puberty. Owing to reduced penetrance of the skin phenotype, cerebral dysgenesis, and neuropathy, we propose renaming this syndrome SNAP29-related disorder.

OR15-04 Central Precocious Puberty without Central Nervous System Lesions: Is It Really Idiopathic?

Background: The etiological diagnosis of central precocious puberty (CPP) has been classically divided into causes with or without central nervous system (CNS) lesions. Among the cases without CNS lesions, most of them are classified as idiopathic. In clinical practice, about 90% of girls and 40% of boys with CPP are considered having the idiopathic form. In the last two decades, pioneering studies have revealed underlying genetic causes in patients with apparently idiopathic CPP.Objective: To describe the frequency of genetic causes identified in a large cohort of patients with CPP followed in a single research center and to evaluate its role in the distribution of the etiology of CPP.Patients and methods: A retrospective evaluation was performed analyzing the etiological diagnosis of 276 patients (246 girls, 30 boys) with CPP followed in a single university hospital outpatient clinic from 2006 to 2019. The great majority (230 patients) presented without CNS lesions, being classified as idiopathic CPP group. Among the idiopathic CPP group, 170 of them had DNA samples available and were included for genetic analysis. Patients included for genetic analysis were systematically investigated for genetic causes of CPP using standard methodologies of genetic-molecular analysis. Briefly, they were studied as follows: 120 by Sanger sequencing; 18 by target panel sequencing; 27 by whole-exome sequencing; 5 by whole-genome sequencing; 113 by specific DNA methylation analysis; and 38 by genomic microarray.Results: Among the 276 patients with CPP, 46 (16.7%) had pathological CNS lesions: 19 boys and 27 girls, indicating the prevalence of CPP with CNS lesions (organic) of 63.3% in boys and 11% in girls. The most common cause of organic CPP was hypothalamic hamartoma (20 cases). Meanwhile 230 patients (83.3%) encompassed the apparently idiopathic CPP group. Main characteristics of this idiopathic CPP group were: 219 girls and 11 boys; 158 sporadic (69%), 68 familial (29.5%) and 4 adopted (1.5%). In the subset of patients with DNA available (162 girls, 8 boys), the frequency of genetic causes was 11.8% (20 cases: 18 girls and 2 boys). Analyzing by sex, the frequency of genetic causes was higher in boys (25%) than in girls (11.1%). The identified genetic defects were the following: 9 cases with inactivating MKRN3 mutations (8 families), 6 cases with inactivating DLK1 mutations (2 families), 1 case with activating KISS1R mutation, 1 case with activating KISS1 mutation, 2 sporadic cases with maternal uniparental disomy of chromosome 14, and 1 sporadic case with epimutation at DLK1 locus.Conclusion: Pathogenic genetic defects were identified in 11.8% of patients with apparently idiopathic CPP involving four distinct genes. Altogether, these genetic findings indicate a context of changing in the distribution of the etiological diagnosis of CPP in both sexes, highlighting the genetic causes.

Секвенирование генома у пациентов с вероятно наследственными заболеваниями нервной системы

Технологии секвенирования нового поколения (NGS) имеют важное значение в диагностике заболеваний нервной системы. Преимуществом их использования является широкий охват исследуемых генов, что позволяет повысить выявляемость причин в такой клинически и генетически гетерогенной группе заболеваний. Цель настоящей работы - определить эффективность секвенирования генома для выявления генетических причин у пациентов с вероятно наследственными заболеваниями нервной системы. В нашем исследовании секвенирование генома позволило выявить причину заболевания у 28,6% таких пациентов. При отрицательном результате анализа панели генов секвенирование генома позволило выявить причину заболевания у 9% пациентов. NGS-based technologies play an important role in the diagnosis of diseases of the nervous system. The advantage of their using is the wide coverage of the analyzed genes, which allows to increase the detection of causes in such a clinically and genetically heterogeneous group of diseases. The purpose of this work is to determine the effectiveness of genome sequencing to identify genetic causes in patients with likely hereditary diseases of the nervous system. In our study, genome sequencing revealed the cause of the disease in 28.6%. In cases with a negative result from the analysis of the gene panel, genome sequencing revealed the cause of the disease in 9% of patients.

Location of Balanced Chromosome-Translocation Breakpoints by Long-Read Sequencing on the Oxford Nanopore Platform.

Genomic structural variants, including translocations, inversions, insertions, deletions, and duplications, are challenging to be reliably detected by traditional genomic technologies. In particular, balanced translocations and inversions can neither be identified by microarrays since they do not alter chromosome copy numbers, nor by short-read sequencing because of the unmappability of short reads against repetitive genomic regions. The precise localization of breakpoints is vital for exploring genetic causes in patients with balanced translocations or inversions. Long-read sequencing techniques may detect these structural variants in a more direct, efficient, and accurate manner. Here, we performed whole-genome, long-read sequencing using the Oxford Nanopore GridION sequencer to detect breakpoints in six balanced chromosome translocation carriers and one inversion carrier. The results showed that all the breakpoints were consistent with the karyotype results with only ~10× coverage. Polymerase chain reaction (PCR) and Sanger sequencing confirmed 8 out of 14 breakpoints; however, other breakpoint loci were slightly missed since they were either in highly repetitive regions or pericentromeric regions. Some of the breakpoints interrupted normal gene structure, and in other cases, micro-deletions/insertions were found just next to the breakpoints. We also detected haplotypes around the breakpoint regions. Our results suggest that long-read, whole-genome sequencing is an ideal strategy for precisely localizing translocation breakpoints and providing haplotype information, which is essential for medical genetics and preimplantation genetic testing.

Genetic Basis of Human Congenital Heart Disease.

Congenital heart disease (CHD) is the most common major congenital anomaly with an incidence of ∼1% of live births and is a significant cause of birth defect-related mortality. The genetic mechanisms underlying the development of CHD are complex and remain incompletely understood. Known genetic causes include all classes of genetic variation including chromosomal aneuploidies, copy number variants, and rare and common single-nucleotide variants, which can be either de novo or inherited. Among patients with CHD, ∼8%-12% have a chromosomal abnormality or aneuploidy, between 3% and 25% have a copy number variation, and 3%-5% have a single-gene defect in an established CHD gene with higher likelihood of identifying a genetic cause in patients with nonisolated CHD. These genetic variants disrupt or alter genes that play an important role in normal cardiac development and in some cases have pleiotropic effects on other organs. This work reviews some of the most common genetic causes of CHD as well as what is currently known about the underlying mechanisms.

Diagnostic yield and clinical effects of exome sequencing analysis in patients with early-onset scoliosis

BackgroundScoliosis is clinically defined as a spine deformity with lateral curvature greater than 10° and the cause of the disease is elusive. Early onset scoliosis, defined by an onset age before 10 years, conveys a substantial health risk to affected children. Although exome sequencing has emerged as a first-line diagnostic method for rare diseases, genetic testing is not routinely done for children with early onset scoliosis. We aimed to explore the diagnostic yield of exome sequencing in patients with early onset scoliosis. MethodsWe recruited a Chinese cohort of patients who were clinically diagnosed with early onset scoliosis through the Deciphering disorders Involving Scoliosis and COmorbidities (DISCO). We did exome sequencing on these individuals and available family members. Exome sequencing data were interpreted according to the American College of Medical Genetics and Genomics guidelines. Patients were followed up for a minimum of 2 years. We also recruited an American cohort of 13 patients with clinically diagnosed idiopathic early onset scoliosis, who underwent exome sequencing. FindingsWe recruited 447 patients in the Chinese cohort and 323 (72%) of 447 patients with early onset scoliosis were followed up for a minimum of 2 years. In the Chinese cohort, we detected diagnostic variants in 92 (21%) of 447 patients with early onset scoliosis, encompassing 33 disease-causing genes and five genomic regions. The age at presentation, the number of organ systems involved, and the Cobb angle were the three features that were most predictive of a molecular diagnosis. Notably, 14 (41%) of 34 patients with non-TBX6-associated congenital scoliosis (TACS) molecular diagnoses had a higher post-surgery complication rate than did the 24 (9·2%) of 260 patients who were molecularly undiagnosed (p=0·000008). In the American cohort, one (8%) of 13 patients had a molecular diagnosis of Sotos syndrome, making the total number of patients in whom we found diagnostic variants 93 (20·2%) of 460. InterpretationExome sequencing could identify the genetic cause in patients with early onset scoliosis. Specific clinical features and feature pairs provided indications for genetic testing in these patients. The prevention of post-surgery complications could potentially be implemented for patients with a non-TACS molecular diagnosis. FundingNational Natural Science Foundation of China, Beijing Natural Science Foundation, 2016 Milstein Medical Asian American Partnership Foundation Fellowship Award in Translational Medicine, CAMS Initiative Fund for Medical Sciences, the Central Level Public Interest Program for Scientific Research Institute, the National Key Research and Development Program of China, the National Undergraduates Innovation and Training Program of Peking Union Medical College, US National Institutes of Health, National Institute of Neurological Disorders and Stroke, National Human Genome Research Institute and National Heart, Lung, and Blood Institute, the National Human Genome Research Institute, TX Scottish Rite Hospital Research Fund, Foundation Cotrel, and P01 HD084387.

Variants in MME are associated with autosomal-recessive distal hereditary motor neuropathy.

ObjectiveTo identify a new genetic cause in patients segregating distal hereditary motor neuropathy (dHMN) with an autosomal recessive pattern.MethodsWhole‐exome sequencing was conducted in two siblings and was combined with segregation analysis. Additionally, 83 unrelated dHMN patients with unknown genetic cause were screened. RNA analysis was performed using blood lymphocytes and HEK293 cells transfected with mutant plasmids. Immunohistochemistry and Western blot analysis was applied to the nerve tissue. The enzymatic activities of mutant proteins were measured in the cultured cells to verify the pathogenicity of variants.ResultsThe clinical features of the patients showed late‐onset phenotype of distal motor neuropathy without sensory involvement. We identified that compound heterozygous variants of c.1342C>T and c.2071_2072delGCinsTT in the membrane metalloendopeptidase (MME) gene co‐segregated with the phenotype in a dHMN family. In an additional group of 83 patients with dHMN, compound heterozygous variants of c.1416+2T>C and c.2027C>T in MME were identified in one patient. The splice site variant c.1416+2T>C results in skipping of exon 13. The stop variant c.1342C>T induces mRNA degradation via nonsense‐mediated mRNA decay. Transcript levels of MME in the lymphocytes showed no significant differences between the patients and controls. We also identified that MME variants were associated with mild decrease in protein expression in the sural nerve and significant impairments of enzymatic activity.InterpretationVariants in the MME gene were associated with not only a Charcot‐Marie‐Tooth neuropathy phenotype but also with an autosomal‐recessive dHMN phenotype. Loss of function may play a role in the pathogenesis of dHMN.

Comprehensive Genetic Results for Primary Immunodeficiency Disorders in a Highly Consanguineous Population.

Objective: To present the genetic causes of patients with primary immune deficiencies (PIDs) in Kuwait between 2004 and 2017.Methods: The data was obtained from the Kuwait National Primary Immunodeficiency Disorders Registry. Genomic DNA from patients with clinical and immunological features of PID was sequenced using Sanger sequencing (SS), next generation sequencing (NGS) of targeted genes, whole exome sequencing (WES), and/or whole genome sequencing (WGS). Functional assays were utilized to assess the biologic effect of identified variants. Fluorescence in situ hybridization (FISH) for 22q11.2 deletion and genomic hybridizations arrays were performed when thymic defects were suspected.Results: A total of 264 patients were registered during the study period with predominance of patients with immunodeficiencies affecting cellular and humoral immunity (35.2%), followed by combined immunodeficiencies with associated syndromic features (24%). Parental consanguinity and family history suggestive of PID were reported in 213 (81%) and 145 patients (55%), respectively. Genetic testing of 206 patients resulted in a diagnostic yield of 70%. Mutations were identified in 46 different genes and more than 90% of the reported genetic defects were transmitted by in an autosomal recessive pattern. The majority of the mutations were missense mutations (57%) followed by deletions and frame shift mutations. Five novel disease-causing genes were discovered.Conclusions: Genetic testing should be an integral part in the management of primary immunodeficiency patients. This will help the delivery of precision medicine and facilitate proper genetic counseling. Studying inbred populations using sophisticated diagnostic methods can allow better understanding of the genetics of primary immunodeficiency disorders.

Genetic landscape of pediatric movement disorders and management implications.

ObjectiveTo identify underlying genetic causes in patients with pediatric movement disorders by genetic investigations.MethodsAll patients with a movement disorder seen in a single Pediatric Genetic Movement Disorder Clinic were included in this retrospective cohort study. We reviewed electronic patient charts for clinical, neuroimaging, biochemical, and molecular genetic features. DNA samples were used for targeted direct sequencing, targeted next-generation sequencing, or whole exome sequencing.ResultsThere were 51 patients in the Pediatric Genetic Movement Disorder Clinic. Twenty-five patients had dystonia, 27 patients had ataxia, 7 patients had chorea-athetosis, 8 patients had tremor, and 7 patients had hyperkinetic movements. A genetic diagnosis was confirmed in 26 patients, including in 20 patients with ataxia and 6 patients with dystonia. Targeted next-generation sequencing panels confirmed a genetic diagnosis in 9 patients, and whole exome sequencing identified a genetic diagnosis in 14 patients.ConclusionsWe report a genetic diagnosis in 26 (51%) patients with pediatric movement disorders seen in a single Pediatric Genetic Movement Disorder Clinic. A genetic diagnosis provided either disease-specific treatment or effected management in 10 patients with a genetic diagnosis, highlighting the importance of early and specific diagnosis.