Genetic counseling for the dystrophinopathies-Practice resource of the National Society of Genetic Counselors.

The dystrophinopathies encompass the phenotypically variable forms of muscular dystrophy caused by pathogenic variants in the DMD gene. The dystrophinopathies include the most common inherited muscular dystrophy among 46,XY individuals, Duchenne muscular dystrophy, as well as Becker muscular dystrophy and other less common phenotypic variants. With increased access to and utilization of genetic testing in the diagnostic and carrier setting, genetic counselors and clinicians in diverse specialty areas may care for individuals with and carriers of dystrophinopathy. This practice resource was developed as a tool for genetic counselors and other health care professionals to support counseling regarding dystrophinopathies, including diagnosis, health risks and management, psychosocial needs, reproductive options, clinical trials, and treatment. Genetic testing efforts have enabled genotype/phenotype correlation in the dystrophinopathies, but have also revealed unexpected findings, further complicating genetic counseling for this group of conditions. Additionally, the therapeutic landscape for dystrophinopathies has dramatically changed with several FDA-approved therapeutics, an expansive research pathway, and numerous clinical trials. Genotype-phenotype correlations are especially complex and genetic counselors' unique skill sets are useful in exploring and explaining this to families. Given the recent advances in diagnostic testing and therapeutics related to dystrophinopathies, this practice resource is a timely update for genetic counselors and other healthcare professionals involved in the diagnosis and care of individuals with dystrophinopathies.

An evaluation of clinical presentation and genetic testing approaches for patients with neuromuscular disorders.

Inherited neuromuscular disorders (NMDs) are a large group of genetic conditions characterized by impaired peripheral nerve, motor neuron, neuromuscular junction, or skeletal muscle function. These conditions are also known to have clinical and genetic heterogeneity and variable ages of onset. Clinical evaluation for NMDs has increasingly incorporated molecular genetics. However, genetic testing is complicated by the variety of testing options and the ambiguity of NMD phenotypes. Examining test selection and yield may elucidate testing recommendations and improve the diagnostic journey for these patients. This retrospective chart review evaluated the clinical presentations, genetic testing approaches, and diagnostic outcomes of 155 patients with suspected NMDs at Cincinnati Children's Hospital Medical Center. A total of 262 individual tests were ordered, averaging 1.7 tests per patient. The clinic utilized 26 separate genetic tests, with test yields ranging from 0% to 66%. Overall, 21% of patients received a genetic diagnosis. Of all the clinical findings evaluated, elevated CPK levels with or without muscle weakness were the most informative symptoms correlated with a diagnostic result. This study highlights several genetic testing considerations for NMDs, including the variability of diagnostic outcomes. This knowledge is relevant to clinicians and patients, especially during the pretest counseling and consenting process.

Identification of Biallelic dystrophin gene variants during maternal carrier testing for Becker muscular dystrophy and review of the DMD exon 49-51 deletion phenotype.

BACKGROUND: Dystrophinopathies are X-linked recessive conditions caused by pathogenic variants in the dystrophin (DMD) gene. In a family that included two boys with Becker muscular dystrophy (BMD) due to a DMD deletion of exons 45-47, maternal carrier testing unexpectedly identified biallelic DMD deletions of exons 45-47 and 49-51. METHODS: The patient's mild phenotype in the setting of biallelic DMD variants prompted further investigation of the exon 49-51 deletion in particular, via literature review and retrospective chart review of patients who have been evaluated in our institution's comprehensive neuromuscular center and/or diagnosed in our clinical genetic testing laboratory. RESULTS: To our knowledge, this is only the fifth case of confirmed biallelic DMD variants in a female. In males, the DMD exon 49-51 deletion appears to result in a mild BMD phenotype with low or normal creatine kinase levels. This deletion comprised 19% (4/21) of dystrophinopathies diagnosed by chromosomal microarray (CMA) in males during the past ten years in our clinical laboratory. Most individuals identified by chart review were diagnosed through CMA, despite the fact that microarray was genome-wide and not DMD-specific. This case raised important genetic counseling issues. CONCLUSION: The DMD exon 49-51 deletion appears to cause a variable but generally mild BMD phenotype. Its relatively frequent detection by CMA suggests it may be underdiagnosed.

Clinically available testing options resulting in diagnosis in post-exome clinic at one medical center.

Exome sequencing (ES) became clinically available in 2011 and promised an agnostic, unbiased next-generation sequencing (NGS) platform for patients with symptoms believed to have a genetic etiology. The diagnostic yield of ES has been estimated to be between 25-40% and may be higher in specific clinical scenarios. Those who remain undiagnosed may have no molecular findings of interest on ES, variants of uncertain significance in genes that are linked to human disease, or variants of uncertain significance in candidate genes that are not definitively tied to human disease. Recent evidence suggests that a post-exome evaluation consisting of clinical re-phenotyping, functional studies of candidate variants in known genes, and variant reevaluation can lead to a diagnosis in 5-15% of additional cases. In this brief research study, we present our experience on post-exome evaluations in a cohort of patients who are believed to have a genetic etiology for their symptoms. We have reached a full or partial diagnosis in approximately 18% (6/33) of cases that have completed evaluations to date. We accomplished this by utilizing NGS-based methods that are available on a clinical basis. A sample of these cases highlights the utility of ES reanalysis with updated phenotyping allowing for the discovery of new genes, re-adjudication of known variants, incorporating updated phenotypic information, utilizing functional testing such as targeted RNA sequencing, and deploying other NGS-based testing methods such as gene panels and genome sequencing to reach a diagnosis.

An autosomal dominant neurological disorder caused by de novo variants in FAR1 resulting in uncontrolled synthesis of ether lipids.

PURPOSE: In this study we investigate the disease etiology in 12 patients with de novo variants in FAR1 all resulting in an amino acid change at position 480 (p.Arg480Cys/His/Leu). METHODS: Following next-generation sequencing and clinical phenotyping, functional characterization was performed in patients' fibroblasts using FAR1 enzyme analysis, FAR1 immunoblotting/immunofluorescence, and lipidomics. RESULTS: All patients had spastic paraparesis and bilateral congenital/juvenile cataracts, in most combined with speech and gross motor developmental delay and truncal hypotonia. FAR1 deficiency caused by biallelic variants results in defective ether lipid synthesis and plasmalogen deficiency. In contrast, patients' fibroblasts with the de novo FAR1 variants showed elevated plasmalogen levels. Further functional studies in fibroblasts showed that these variants cause a disruption of the plasmalogen-dependent feedback regulation of FAR1 protein levels leading to uncontrolled ether lipid production. CONCLUSION: Heterozygous de novo variants affecting the Arg480 residue of FAR1 lead to an autosomal dominant disorder with a different disease mechanism than that of recessive FAR1 deficiency and a diametrically opposed biochemical phenotype. Our findings show that for patients with spastic paraparesis and bilateral cataracts, FAR1 should be considered as a candidate gene and added to gene panels for hereditary spastic paraplegia, cerebral palsy, and juvenile cataracts.

Open communication of Duchenne muscular dystrophy facilitates disclosure process by parents to unaffected siblings.

Duchenne muscular dystrophy (DMD) is a progressive childhood onset neuromuscular disease with no known cure. There is extensive literature about the impact of a diagnosis on the psychosocial well-being of unaffected siblings, with a need for additional research to provide information about optimal ways to disclose this information to unaffected children. We sought to explore the parental experiences of disclosing a sibling's diagnosis of DMD to unaffected children who were age 8-17 years old either at the time of their sibling's diagnosis or presently. Parents were recruited through Maryland Muscular Dystrophy Association, Parent Project Muscular Dystrophy, and Cincinnati Children's Hospital Medical Center Neuromuscular Center. An interview guide, rooted in family communication, was created to incorporate themes and topics found in literature specific to DMD and disclosure to unaffected siblings. We qualitatively explored these experiences through semi-structured interviews and performed thematic analysis using a coding system to identify overarching themes and subthemes. Several main themes regarding challenges to the disclosure process emerged. We identified the following themes in procedural aspects of disclosure: lack of provider support, importance of the DMD community, and open and gradual timeline of disclosure. Under emotional experiences, we identified these themes: overwhelming nature, elements of surprise disclosure, and balancing parental and sibling needs. Most questions from unaffected siblings related to procedural elements of care such as treatments and equipment. Additional unanticipated themes emerged that may contribute to the knowledge of family culture surrounding DMD: the complex role of Facebook as a family resource, deferring carrier testing for siblings, and inclusion of DMD in school projects. While the process of disclosure is complicated by a variety of factors such as lack of provider support and overwhelming emotional burden, families highlight the importance of open communication in discussion with unaffected children.

The Clinical Journey of Patients with Riboflavin Transporter Deficiency Type 2.

PURPOSE: To identify symptoms and health care interactions with patients with riboflavin transporter deficiency (RTD) type 2 prior to diagnosis. METHODS: Parents of children with riboflavin transporter deficiency type 2 (n = 10) were interviewed to collect data on the patient's clinical journey. RESULTS: The average diagnostic delay was 27.6 months. Neurologists were the most commonly visited clinician (90%). Common symptoms during the first year of the patient's clinical journey included abnormal gait and/or ataxia (70%), nystagmus (50%), and upper body muscle weakness (40%). Prior to diagnosis, optic atrophy, sleep apnea, breath-holding spells, and dysphagia were commonly observed. Hearing loss was only reported in 40% of subjects prior to diagnosis. Riboflavin responsive megaloblastic anemia is reported for the first time. Mitochondrial disease was the most common suspected diagnosis (30%). CONCLUSION: Despite clinical variability, common early symptoms of riboflavin transporter deficiency type 2 exist that can better allow clinicians to more rapidly identify riboflavin transporter deficiency type 2.

Reduction of Health Care Costs and Improved Appropriateness of Incoming Test Orders: the Impact of Genetic Counselor Review in an Academic Genetic Testing Laboratory.

The goal of this study was to evaluate the impact of genetic counselor (GC) review of incoming test orders received in an academic diagnostic molecular genetics laboratory. The GC team measured the proportion of orders that could be modified to improve efficiency or sensitivity, tracked provider uptake of GC proposed testing changes, and calculated the health care dollar savings resulting from GC intervention. During this 6-month study, the GC team reviewed 2367 incoming test orders. Of these, 109 orders (4.6%) were flagged for review for potentially inefficient or inappropriate test ordering. These flagged orders corresponded to a total of 51 cases (1-5 orders for each patient), representing 54 individuals and including 3 sibling pairs. The GC team proposed a modification for each flagged case and the ordering providers approved the proposed change for 49 of 51 cases (96.08%). For the 49 modifications, the cost savings totaled $98,750.64, for an average of $2015.32 saved per modification. This study provides evidence of the significant contribution of genetic counselors in a laboratory setting and demonstrates the benefit of laboratories working with ordering providers to identify the best test for their patients. The review of test orders by a genetic counselor both improves genetic test ordering strategies and decreases the amount of health care dollars spent on genetic testing.

Genetics professionals' opinions of whole-genome sequencing in the newborn period.

Newborn screening (NBS) programs have been successful in identifying infants with rare, treatable, congenital conditions. While current programs rely largely on biochemical analysis, some predict that in the future, genome sequencing may be used as an adjunct. The purpose of this exploratory pilot study was to begin to characterize genetics professionals' opinions of the use of whole-genome sequencing (WGS) in NBS. We surveyed members of the American College of Medical Genetics and Genomics (ACMG) via an electronic survey distributed through email. The survey included questions about results disclosure, the current NBS paradigm, and the current criteria for adding a condition to the screening panel. The response rate was 7.3 % (n = 113/1549). The majority of respondents (85 %, n = 96/113) felt that WGS should not be currently used in NBS, and that if it were used, it should not be mandatory (86.5 %, n = 96/111). However, 75.7 % (n = 84/111) foresee it as a future use of WGS. Respondents felt that accurate interpretation of results (86.5 %, n = 83/96), a more extensive consent process (72.6 %, n = 69/95), pre- (79.2 %, n = 76/96) and post-test (91.6 %, n = 87/95) counseling, and comparable costs (70.8 %, n = 68/96) and turn-around-times (64.6 %, n = 62/96) to current NBS would be important for using WGS in NBS. Participants were in favor of disclosing most types of results at some point in the lifetime. However, the majority (87.3 %, n = 96/110) also indicated that parents should be able to choose what results are disclosed. Overall, respondents foresee NBS as a future use of WGS, but indicated that WGS should not occur within the framework of traditional NBS. They agreed with the current criteria for including a condition on the recommended uniform screening panel (RUSP). Further discussion about these criteria is needed in order to better understand how they could be utilized if WGS is incorporated into NBS.

Developmental functions for the Caenorhabditis elegans Sp protein SPTF-3.

Sp factors are important for animal development and the transcriptional regulation of a wide variety of genes. How they influence the developmental decisions of individual cells within the organism, however, is poorly understood. To better understand the developmental functions for Sp transcription factors, we have characterized the functions of Caenorhabditis elegans SPTF-3 using RNAi knockdown and a non-null, hypomorphic mutant allele. We find that disruption of sptf-3 confers a variety of developmental defects, including defects in development of the egg-laying system, oocyte production, and embryonic morphogenesis. sptf-3 mutants exhibit defects in vulval lineage polarity, a phenotype previously only observed in mutants defective in Wnt signaling. We show that the embryonic function of sptf-3 is dependent on germline activity, arguing that the gene has an important maternal contribution to embryonic development. An evaluation of reporter gene expression suggests that SPTF-3 exhibits specificity, in that it can influence the expression of a given gene in some cells but not others, and that SPTF-3 participates in the maintenance of gene expression states in differentiated cells. We propose SPTF-3 provides a good model to study the in vivo functions for Sp transcription factors during animal development.