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Purpose To characterize the molecular genetics of autosomal recessive Noonan syndrome. Methods Families underwent phenotyping for features of Noonan syndrome in children and their parents. Two multiplex families underwent linkage analysis. Exome, genome, or multigene panel sequencing was used to identify variants. The molecular consequences of observed splice variants were evaluated by reverse-transcription polymerase chain reaction. Results Twelve families with a total of 23 affected children with features of Noonan syndrome were evaluated. The phenotypic range included mildly affected patients, but it was lethal in some, with cardiac disease and leukemia. All of the parents were unaffected. Linkage analysis using a recessive model supported a candidate region in chromosome 22q11, which includes LZTR1 , previously shown to harbor mutations in patients with Noonan syndrome inherited in a dominant pattern. Sequencing analyses of 21 live-born patients and a stillbirth identified biallelic pathogenic variants in LZTR1 , including putative loss-of-function, missense, and canonical and noncanonical splicing variants in the affected children, with heterozygous, clinically unaffected parents and heterozygous or normal genotypes in unaffected siblings. Conclusion These clinical and genetic data confirm the existence of a form of Noonan syndrome that is inherited in an autosomal recessive pattern and identify biallelic mutations in LZTR1 .

Background Disorders of sex development (DSD) are congenital conditions in which chromosomal, gonadal, or phenotypic sex is atypical. Clinical management of DSD is often difficult and currently only 13% of patients receive an accurate clinical genetic diagnosis. To address this we have developed a massively parallel sequencing targeted DSD gene panel which allows us to sequence all 64 known diagnostic DSD genes and candidate genes simultaneously. Results We analyzed DNA from the largest reported international cohort of patients with DSD (278 patients with 46,XY DSD and 48 with 46,XX DSD). Our targeted gene panel compares favorably with other sequencing platforms. We found a total of 28 diagnostic genes that are implicated in DSD, highlighting the genetic spectrum of this disorder. Sequencing revealed 93 previously unreported DSD gene variants. Overall, we identified a likely genetic diagnosis in 43% of patients with 46,XY DSD. In patients with 46,XY disorders of androgen synthesis and action the genetic diagnosis rate reached 60%. Surprisingly, little difference in diagnostic rate was observed between singletons and trios. In many cases our findings are informative as to the likely cause of the DSD, which will facilitate clinical management. Conclusions Our massively parallel sequencing targeted DSD gene panel represents an economical means of improving the genetic diagnostic capability for patients affected by DSD. Implementation of this panel in a large cohort of patients has expanded our understanding of the underlying genetic etiology of DSD. The inclusion of research candidate genes also provides an invaluable resource for future identification of novel genes.

Background Family genetic testing of patients newly diagnosed with a rare genetic disease can improve early diagnosis of family members, allowing patients to receive disease‐specific therapies when available. Fabry disease, an X‐linked lysosomal storage disorder caused by pathogenic variants in GLA, can lead to end‐stage renal disease, cardiac arrhythmias, and stroke. Diagnostic delays are common due to the rarity of the disease and non‐specificity of early symptoms. Newborn screening and screening of at‐risk populations, (e.g., patients with hypertrophic cardiomyopathy or undiagnosed nephropathies) can identify individuals with Fabry disease. Subsequent cascade genotyping of family members may disclose a greater number of affected individuals, often at younger age than they would have been diagnosed otherwise. Methods We conducted a literature search to identify all published data on family genetic testing for Fabry disease, and discussed these data, experts’ own experiences with family genetic testing, and the barriers to this type of screening that are present in their respective countries. Results There are potential barriers that make implementation of family genetic testing challenging in some countries. These include associated costs and low awareness of its importance, and cultural and societal issues. Regionally, there are barriers associated with population educational levels, national geography and infrastructures, and a lack of medical geneticists. Conclusion In this review, the worldwide experience of an international group of experts of Fabry disease highlights the issues faced in the family genetic testing of patients affected with rare genetic diseases. This review article discusses the literature published on family genetic testing for Fabry disease and the experiences of 19 Fabry experts from 15 countries regarding family screening in their countries and the barriers they are facing. Together, this literature overview and combined global experience provides valuable insights to medical geneticists working to improve the diagnosis of rare diseases within their countries and globally.

CLAN (Caring and Living as Neighbours) is an Australian-based non-governmental organisation (NGO) committed to equity for children living with chronic health conditions in resource-poor settings. Since 2004, CLAN has collaborated with a broad range of partners across the Asia Pacific region to improve quality of life for children living with congenital adrenal hyperplasia (CAH). This exploratory case study uses the Knowledge to Action (KTA) framework to analyse CLAN’s activities for children living with CAH in the Asia Pacific. The seven stages of the KTA action cycle inform a systematic examination of comprehensive, collaborative, sustained actions to address a complex health challenge. The KTA framework demonstrates the “how” of CLAN’s approach to knowledge creation and exchange, and the centrality of community development to multisectoral collaborative action across a range of conditions, cultures and countries to redressing child health inequities. This includes a commitment to: affordable access to essential medicines and equipment; education, research and advocacy; optimisation of medical management; encouragement of family support groups; efforts to reduce financial burdens; and ethical, transparent program management as critical components of success. Improvements in quality of life and health outcomes are achievable for children living with CAH and other chronic health conditions in resource-poor settings. CLAN’s strategic framework for action offers a model for those committed to #LeaveNoChildBehind.

Disorders of sex development (DSDs) are conditions affecting development of the gonads or genitalia. Variants in two key genes, SRY and its target SOX9 , are an established cause of 46,XY DSD, but the genetic basis of many DSDs remains unknown. SRY-mediated SOX9 upregulation in the early gonad is crucial for testis development, yet the regulatory elements underlying this have not been identified in humans. Here, we identified four DSD patients with overlapping duplications or deletions upstream of SOX9 . Bioinformatic analysis identified three putative enhancers for SOX9 that responded to different combinations of testis-specific regulators. All three enhancers showed synergistic activity and together drive SOX9 in the testis. This is the first study to identify SOX9 enhancers that, when duplicated or deleted, result in 46,XX or 46,XY sex reversal, respectively. These enhancers provide a hitherto missing link by which SRY activates SOX9 in humans, and establish SOX9 enhancer mutations as a significant cause of DSD. SRY and its target SOX9 are known key determinants in testis development. Here the authors by studying duplications and deletions upstream of SOX9 from patient samples with disorders of sex development (DSD) reveal enhancers for SOX9 critical for human sex development and DSD.

BackgroundGenomic imprinting results from the resistance of germline epigenetic marks to reprogramming in the early embryo for a small number of mammalian genes. Genetic, epigenetic or environmental insults that prevent imprints from evading reprogramming may result in imprinting disorders, which impact growth, development, behaviour and metabolism. We aimed to identify genetic defects causing imprinting disorders by whole-exome sequencing in families with one or more members affected by multilocus imprinting disturbance.MethodsWhole-exome sequencing was performed in 38 pedigrees where probands had multilocus imprinting disturbance, in five of whom maternal variants in NLRP5 have previously been found.ResultsWe now report 15 further pedigrees in which offspring had disturbance of imprinting, while their mothers had rare, predicted-deleterious variants in maternal effect genes, including NLRP2, NLRP7 and PADI6. As well as clinical features of well-recognised imprinting disorders, some offspring had additional features including developmental delay, behavioural problems and discordant monozygotic twinning, while some mothers had reproductive problems including pregnancy loss.ConclusionThe identification of 20 putative maternal effect variants in 38 families affected by multilocus imprinting disorders adds to the evidence that maternal genetic factors affect oocyte fitness and thus offspring development. Testing for maternal-effect genetic variants should be considered in families affected by atypical imprinting disorders.

46,XY disorders of sex development (46,XY DSD) are genetically heterogeneous conditions. Recently, a few submicroscopic genomic rearrangements have been reported as novel genetic causes of 46,XY DSD. To clarify the role of cryptic rearrangements in the development of 46,XY DSD, we performed array-based comparative genomic hybridization analysis for 24 genetic males with genital abnormalities. Heterozygous submicroscopic deletions were identified in three cases (cases 1-3). A ∼8.5 Mb terminal deletion at 9p24.1-24.3 was detected in case 1 that presented with complete female-type external genitalia and mental retardation; a ∼2.0 Mb interstitial deletion at 20p13 was identified in case 2 with ambiguous external genitalia and short stature; and a ∼18.0 Mb interstitial deletion at 2q31.1-32 was found in case 3 with ambiguous external genitalia, mental retardation and multiple anomalies. The genital abnormalities of case 1 could be ascribed to gonadal dysgenesis caused by haploinsufficiency of DMRT1, while those of case 3 were possibly associated with perturbed organogenesis due to a deletion of the HOXD cluster. The deletion in case 2 affected 36 genes, none of which have been previously implicated in sex development. The results indicate that cryptic genomic rearrangements constitute an important part of the molecular bases of 46,XY DSD and that submicroscopic deletions can lead to various types of 46,XY DSD that occur as components of contiguous gene deletion syndromes. Most importantly, our data provide a novel candidate locus for 46,XY DSD at 20p13.

Background and Objectives: Hyperornithinemia–hyperammonemia–homocitrullinuria syndrome (HHH; OMIM 238970) is one of the rare urea cycle disorders. Ornithine carrier 1 deficiency causes HHH syndrome, characterized by failure of mitochondrial ornithine uptake, hyperammonemia, and accumulation of ornithine and lysine in the cytoplasm. The initial presentation and time of diagnosis in HHH highly varies. Genetic analysis is critical for diagnosis. Materials and Methods: This study encompassed retrospective and prospective analyses of four unrelated Vietnamese children diagnosed with HHH syndrome. Results: The age of diagnosis ranged from 10 days to 46 months. All four cases demonstrated hyperornithinemia and prolonged prothrombin time. Three out of four cases presented with hyperammonemia, elevated transaminases, and uraciluria. No homocitrulline was detected in the urine. Only one case depicted oroticaciduria. Genetic analyses revealed three pathogenic variants in the SLC25A15 gene, with the c.535C>T (p.Arg179*) variant common in Vietnamese patients. The c.562_564del (p.Phe188del) and c.408del (p.Met137Cysfs*10) variants were detected in one case. The latter variant has yet to be reported in the literature on HHH patients. After intervention with a protein-restricted diet, ammonia-reducing therapy, and L-carnitine supplementation, hyperammonemia was not observed, and liver enzyme levels returned to normal. Conclusions: Our results highlighted the clinical and biochemical heterogeneity of HHH syndrome and posed that HHH syndrome should be considered when individuals have hyperammonemia, elevated transaminase, and decreased prothrombin time.

Background/Objectives: Children with congenital adrenal hyperplasia (CAH) face significant risks of impaired growth and metabolic disturbances despite standard glucocorticoid therapy. This cross-sectional study aimed to evaluate growth outcomes, nutritional status, and associated factors among children with CAH treated in a Vietnamese tertiary pediatric center. Methods: We assessed 201 children aged 1.1–16.5 years in a tertiary pediatric center in Vietnam for anthropometric parameters, biochemical markers (calcium, phosphate, 25-hydroxyvitamin D), and clinical features. Growth status was evaluated using WHO standards, and bone age was assessed radiographically. Statistical analyses explored associations between growth outcomes and clinical, biochemical, and treatment-related factors. Results: Stunting was present in 16.4% of children, while 53.3% were overweight or obese. Bone age advancement occurred in 51.7% of cases. Vitamin D insufficiency or deficiency was detected in 85.6% of patients, and hypocalcemia was present in 85.1%. Overweight/obesity, vitamin D deficiency, and bone age advancement were associated with older age, prolonged corticosteroid therapy, higher androgen levels, and clinical features of treatment imbalance (e.g., Cushingoid appearance, hyperpigmentation). Female sex was significantly associated with higher rates of stunting. Conclusions: Growth impairment, nutritional deficiencies, and skeletal maturation disturbances are prevalent among children with CAH in Vietnam. Early identification of risk factors and the implementation of tailored management strategies that address both endocrine and nutritional health are crucial for optimizing long-term outcomes.