Elicia Estrella

The pediatric diagnostic odyssey is a period of uncertainty and emotional turmoil for families, often characterized by multiple minor medical procedures (such as venipuncture) that children may find distressing. Interventions to reduce distress are rarely offered, despite evidence that this is crucial both for avoiding anticipatory anxiety before future procedures and for improving healthcare compliance in adulthood. We interviewed ten mothers of children with neuromuscular disorders, asking about their perceptions of their child's experiences with different medical procedures, the emotional impact of the diagnostic odyssey, implications of obtaining a diagnosis, and interactions with healthcare providers. We coded interviews in ATLAS.ti (version 7.0) based on a priori and emergent themes, and analyzed them based on the principles of interpretive description. We found that predicting and assessing children's reactions to procedures is challenging; parents reported non‐invasive procedures such as x‐rays were distressing for some children, and that providers did not detect subtle indicators of distress. Parents valued obtaining a diagnosis because it validated their concerns, enabled planning for the child's future healthcare needs, and allowed access to established support networks. This study suggests that healthcare providers can improve the experience of the diagnostic odyssey by validating family concerns and connecting them to support services that are available without a diagnosis.

Many individuals with muscular dystrophies remain genetically undiagnosed despite clinical diagnostic testing, including exome sequencing. Some may harbor previously undetected structural variants (SVs) or cryptic splice sites. We enrolled 10 unrelated families: nine had muscular dystrophy but lacked complete genetic diagnoses and one had an asymptomatic DMD duplication. Nanopore genomic long‐read sequencing identified previously undetected pathogenic variants in four individuals: an SV in DMD, an SV in LAMA2, and two single nucleotide variants in DMD that alter splicing. The DMD duplication in the asymptomatic individual was in tandem. Nanopore sequencing may help streamline genetic diagnostic approaches for muscular dystrophy.

Spinal muscular atrophy (SMA) is an autosomal recessive genetic disease characterized by muscle weakness and atrophy with usually typical cognition. The first disease‐modifying therapy for SMA, nusinersen, was approved by the United States Food and Drug Administration (FDA) in 2016 and leads to improved outcomes, especially when administered presymptomatically. Population‐wide carrier screening and newborn screening (NBS) are now recommended by several professional organizations to promote reproductive autonomy, early diagnosis, and treatment. Prenatal genetic counselors (GCs) are important providers of the SMA screening and diagnosis process, but the possible impact of nusinersen on their practice has not been explored. A survey of 182 prenatal GCs in the United States (US) assessed baseline knowledge of nusinersen and likelihood of discussing this option with prospective parents. The majority of GCs (94.5%) were aware of this drug, and almost all (87.3%) felt that this information...

Massachusetts began newborn screening (NBS) for Spinal Muscular Atrophy (SMA) following the availability of new treatment options. The New England Newborn Screening Program developed, validated, and implemented a screening algorithm for the detection of SMA-affected infants who show absent SMN1 Exon 7 by Real-Time™ quantitative PCR (qPCR). We screened 179,467 neonates and identified 9 SMA-affected infants, all of whom were referred to a specialist by day of life 6 (average and median 4 days of life). Another ten SMN1 hybrids were observed but never referred. The nine referred infants who were confirmed to have SMA were entered into treatment protocols. Early data show that some SMA-affected children have remained asymptomatic and are meeting developmental milestones and some have mild to moderate delays. The Massachusetts experience demonstrates that SMA NBS is feasible, can be implemented on a population basis, and helps engage infants for early treatment to maximize benefit.

The differential diagnosis of a child with a suspected neuromuscular disease is vast, given the continued proliferation of disease entities, particularly those that are inherited. Correspondingly, clinical genetic testing has become both increasingly sophisticated and simultaneously more accessible, which has led to clear diagnoses for many patients but confusion for others. Variants of unknown significance (abbreviated VUS or VOUS) on genetic test reports have become notorious for generating diagnostic uncertainty, along with other findings such as a single pathogenic heterozygous variant in a gene that is associated with a recessive disease. The practical implications of correct and prompt diagnoses of inherited neuromuscular diseases have become more apparent in recent years, as the US Food and Drug Administration has approved three new treatments for 5q spinal muscular atrophy (SMA) and four new treatments for Duchenne muscular dystrophy (DMD), all since 2016. Numerous other therapies for inherited neuromuscular diseases are in the pipeline. Is there a single clinical genetic test that can diagnose all inherited neuromuscular diseases? The answer is not yet. The study by Herman et al in this issue of the journal describes the diagnostic outcomes of 79 children with suspected neuromuscular disease who underwent exome sequencing from a total cohort of 106. Exome sequencing detected definitive genetic diagnoses in 36 of the 79 children. Others in the cohort of 106 patients were diagnosed using chromosomal microarray (9%) and candidate gene testing (20%). A significant number of individuals, however, remained undiagnosed after various combinations of these genetic evaluations. The results agree with findings from targeted sequence capture panels used in clinical diagnostic laboratories for neuromuscular diseases in general (diagnostic yield 46%), and for limb-girdle muscular dystrophy (LGMD) in particular (diagnostic yield 27%). For exome sequencing in research settings the numbers skew the other way, with a diagnostic yield of 12.9% for neuromuscular diseases in general, and 40% to 45% for LGMD. In general, whether looking at neuromuscular diseases overall vs specific disease categories such as LGMD, clinical vs research settings, or targeted sequence capture vs exome technologies, it is difficult for short-read next-generation sequencing approaches to yield diagnoses in over 50% of any given neuromuscular cohort, in part due to the ever-proliferating numbers of genes associated with these diseases. In contrast to the commonly used forms of next-generation sequencing, which involve short sequence reads and are sometimes referred to as second-generation sequencing, the generation of much longer raw sequence reads is now possible with the implementation of thirdgeneration techniques. How can we crack this 50% diagnostic ceiling? One key task is to resolve the endless stream of VUS/VOUSs that emerge from genetic test reports. Before any computational analyses are considered, a clinician should think about whether a gene affected by a VUS/VOUS is associated with the patient's phenotype, or at least a similar phenotype. In rare cases, a new phenotype for a gene may be emerging, but in most cases pathogenic variants are found in genes that have previously been associated with the phenotype in question. In cases of suspected neuromuscular disease without a clear-cut genetic diagnosis after the initial round of clinical genetic testing, it is important for the neuromuscular physician to perform a comprehensive diagnostic/ phenotypic analysis, which, aside from a thorough history, threegeneration family history and physical examination may include a combination of a serum creatine kinase level and other serum/urine markers, electrodiagnostic studies, muscle imaging via MRI or ultrasound, and muscle biopsy. For computational analyses of VUS/VOUSs, a key statistic to look up is the allele frequency of single-nucleotide variants, which can be found in a number of publicly accessible databases, one of the largest being the genome aggregation database (gnomAD). Pathogenic variants for Mendelian diseases are typically quite rare, barring founder effects in sequestered communities. Conservation of affected amino acid residues across species also supports pathogenicity; this can be assessed by first by looking up amino acid sequences of interest in a database such as UniProt and then checking sequence alignment using an online tool such as Clustal Omega. A third variable that is frequently assessed is the predicted damaging effect, if any, on the protein structure. There are several commonly used online programs, each with a different algorithm, such as SIFT, PolyPhen2, FATHMM, PROVEAN, and MutationTaster. In many cases these programs will yield conflicting results, so this analysis is most useful when all or most of the prediction programs are in agreement. In silico visualizations of protein crystal structures using…

ObjectiveThe objective of this study is to identify the genetic cause of disease in a congenital form of congenital spinal muscular atrophy and arthrogryposis (CSMAA).MethodsA 2-year-old boy was diagnosed with arthrogryposis multiplex congenita, severe skeletal abnormalities, torticollis, vocal cord paralysis and diminished lower limb movement. Whole exome sequencing was performed on the proband and family members. In silico modeling of protein structure and heterologous protein expression and cytotoxicity assays were performed to validate pathogenicity of the identified variant.ResultsWhole exome sequencing revealed a homozygous mutation in the TRPV4 gene (c.281C>T; p.S94L). The identification of a recessive mutation in TRPV4 extends the spectrum of mutations in recessive forms of the TRPV4-associated disease. p.S94L and other previously identified TRPV4 variants in different protein domains were compared in structural modeling and functional studies. In silico structural modeli...

Next-generation sequencing is commonly used to screen for pathogenic mutations in families with Mendelian disorders, but due to the pace of discoveries, gaps have widened for some diseases between genetic and pathophysiological knowledge. We recruited and analyzed 16 families with limb-girdle muscular dystrophy (LGMD) of Arab descent from Saudi Arabia and Sudan who did not have confirmed genetic diagnoses. The analysis included both traditional and next-generation sequencing approaches. Cellular and metabolic studies were performed on Pyroxd1 siRNA C2C12 myoblasts and controls. Pathogenic mutations were identified in eight of the 16 families. One Sudanese family of Arab descent residing in Saudi Arabia harbored a homozygous c.464A>G, p.Asn155Ser mutation in PYROXD1, a gene recently reported in association with myofibrillar myopathy and whose protein product reduces thiol residues. Pyroxd1 deficiency in murine C2C12 myoblasts yielded evidence for impairments of cellular proliferat...

Exome and whole-genome sequencing are becoming increasingly routine approaches in Mendelian disease diagnosis. Despite their success, the current diagnostic rate for genomic analyses across a variety of rare diseases is approximately 25-50%. Here, we explore the utility of transcriptome sequencing (RNA-seq) as a complementary diagnostic tool in a cohort of 50 patients with genetically undiagnosed rare muscle disorders. We describe an integrated approach to analyze patient muscle RNA-seq, leveraging an analysis framework focused on the detection of transcript-level changes that are unique to the patient compared to over 180 control skeletal muscle samples. We demonstrate the power of RNA-seq to validate candidate splice-disrupting mutations and to identify splice-altering variants in both exonic and deep intronic regions, yielding an overall diagnosis rate of 35%. We also report the discovery of a highly recurrentde novointronic mutation inCOL6A1that results in a dominantly acting sp...

The genetic causes of limb-girdle muscular dystrophy (LGMD) have been studied in numerous countries, but such investigations have been limited in Egypt. A cohort of 30 families with suspected LGMD from Assiut, Egypt, was studied using immunohistochemistry, homozygosity mapping, Sanger sequencing, and whole exome sequencing. Six families were confirmed to have pathogenic mutations, 4 in SGCA and 2 in DMD. Of these, 3 families harbored a single nonsense mutation in SGCA, suggesting that this may be a common mutation in Assiut, Egypt, originating from a founder effect. The Assiut region in Egypt appears to share at least several of the common LGMD genes found in other parts of the world. It is notable that 4 of the 6 mutations were ascertained via whole exome sequencing, even though it was the last approach adopted. This illustrates the power of this technique for identifying causative mutations for muscular dystrophies. This article is protected by copyright. All rights reserved.

Background Duchenne muscular dystrophy (DMD) is an X-linked myopathy resulting from the production of a nonfunctional dystrophin protein. MicroRNA (miRNA) are small 21- to 24-nucleotide RNA that can regulate both individual genes and entire cell signaling pathways. Previously, we identified several mRNA, both muscle-enriched and inflammation-induced, that are dysregulated in the skeletal muscles of DMD patients. One particularly muscle-enriched miRNA, miR-486, is significantly downregulated in dystrophin-deficient mouse and human skeletal muscles. miR-486 is embedded within the ANKYRIN1(ANK1) gene locus, which is transcribed as either a long (erythroid-enriched) or a short (heart muscle- and skeletal muscle-enriched) isoform, depending on the cell and tissue types. Results Inhibition of miR-486 in normal muscle myoblasts results in inhibited migration and failure to repair a wound in primary myoblast cell cultures. Conversely, overexpression of miR-486 in primary myoblast cell cultu...

The pediatric diagnostic odyssey is a period of uncertainty and emotional turmoil for families, often characterized by multiple minor medical procedures (such as venipuncture) that children may find distressing. Interventions to reduce distress are rarely offered, despite evidence that this is crucial both for avoiding anticipatory anxiety before future procedures and for improving healthcare compliance in adulthood. We interviewed ten mothers of children with neuromuscular disorders, asking about their perceptions of their child's experiences with different medical procedures, the emotional impact of the diagnostic odyssey, implications of obtaining a diagnosis, and interactions with healthcare providers. We coded interviews in ATLAS.ti (version 7.0) based on a priori and emergent themes, and analyzed them based on the principles of interpretive description. We found that predicting and assessing children's reactions to procedures is challenging; parents reported non-invasive procedures such as x-rays were distressing for some children, and that providers did not detect subtle indicators of distress. Parents valued obtaining a diagnosis because it validated their concerns, enabled planning for the child's future healthcare needs, and allowed access to established support networks. This study suggests that healthcare providers can improve the experience of the diagnostic odyssey by validating family concerns and connecting them to support services that are available without a diagnosis.

We ascertained a nuclear family in which three of four siblings were affected with an unclassified autosomal recessive myopathy characterized by severe weakness, respiratory impairment, scoliosis, joint contractures, and an unusual combination of dystrophic and myopathic features on muscle biopsy. Whole genome sequence from one affected subject was filtered using linkage data and variant databases. A single gene, MEGF10, contained nonsynonymous mutations that co-segregated with the phenotype. Affected subjects were compound heterozygous for missense mutations c.976T > C (p.C326R) and c.2320T > C (p.C774R). Screening the MEGF10 open reading frame in 190 patients with genetically unexplained myopathies revealed a heterozygous mutation, c.211C > T (p.R71W), in one additional subject with a similar clinical and histological presentation as the discovery family. All three mutations were absent from at least 645 genotyped unaffected control subjects. MEGF10 contains 17 atypical e...

Background There is a marked variation in clinical phenotypes that have been associated with mutations in FKRP, ranging from severe congenital muscular dystrophies to limb-girdle muscular dystrophy type 2I (LGMD2I). Methods We screened the FKRP gene in two cohorts totaling 87 patients with the LGMD phenotype. Results The c.826C>A, p.L276I mutation was present in six patients and a compound heterozygote mutation in a seventh patient. Six patients had a mild LGMD2I phenotype, which resembles that of Becker muscular dystrophy. The other patient had onset before the age of 3 years, and thus may follow a more severe course. Conclusion These findings suggest that LGMD2I may be common in certain North American populations. This diagnosis should be considered early in the evaluation of LGMD.

We describe a unique case of a newborn with Prader-Willi syndrome who presented with fetal goiter as well as neonatal thyroid abnormalities, marked hypotonia, and thrombocytopenia. These new clinical observations may correlate with the uniparental monodisomy form of inheritance of this genetic condition.

Background— The importance of germ-line mosaicism in genetic disease is probably underestimated, even though recent studies indicate that it may be involved in 10% to 20% of apparently de novo cases of several dominantly inherited genetic diseases. Methods and Results— We describe here a case of repeated germ-line transmission of a severe form of long-QT syndrome (LQTS) from an asymptomatic mother with mosaicism for a mutation in the cardiac sodium channel, SCN5A . A male infant was diagnosed with ventricular arrhythmias and cardiac decompensation in utero at 28 weeks and with LQTS after birth, ultimately requiring cardiac transplantation for control of ventricular tachycardia. The mother had no ECG abnormalities, but her only previous pregnancy had ended in stillbirth with evidence of cardiac decompensation at 7 months’ gestation. A third pregnancy also ended in stillbirth at 7 months, again with nonimmune fetal hydrops. The surviving infant was found to have a heterozygous mutatio...

The current study characterizes a cohort of limb-girdle muscular dystrophy (LGMD) in the United States using whole-exome sequencing. Fifty-five families affected by LGMD were recruited using an institutionally approved protocol. Exome sequencing was performed on probands and selected parental samples. Pathogenic mutations and cosegregation patterns were confirmed by Sanger sequencing. Twenty-two families (40%) had novel and previously reported pathogenic mutations, primarily in LGMD genes, and also in genes for Duchenne muscular dystrophy, facioscapulohumeral muscular dystrophy, congenital myopathy, myofibrillar myopathy, inclusion body myopathy and Pompe disease. One family was diagnosed via clinical testing. Dominant mutations were identified in COL6A1, COL6A3, FLNC, LMNA, RYR1, SMCHD1 and VCP, recessive mutations in ANO5, CAPN3, GAA, LAMA2, SGCA and SGCG, and X-linked mutations in DMD. A previously reported variant in DMD was confirmed to be benign. Exome sequencing is a powerful...