Publications by authors named "Sabrina W Yum"

42 Publications

Association Between Body Mass Index and Disability in Children With Charcot-Marie-Tooth Disease.

Neurology 2021 10 7;97(17):e1727-e1736. Epub 2021 Sep 7.

From the University of Sydney (G.A.D., S.P.G., M.P.M.), Faculty of Medicine and Health; Children's Hospital at Westmead (G.A.D., S.P.G., K.M.D.C., J.B., M.P.M.); University of Sydney (K.M.D.C., M.J.M., J.B.), School of Health Sciences; Faculty of Health and Medicine (J.N.B.), University of Newcastle, Australia; Departments of Pediatrics (R.R.S.) and Neurology (M.E.S.), Carver College of Medicine, University of Iowa, Iowa City; Division of Neurology (S.W.Y.) and Department of Occupational Therapy (T.E.), Children's Hospital of Philadelphia; Department of Neurology (S.W.Y., T.E.), Perelman School of Medicine, University of Pennsylvania, Philadelphia; Fondazione IRCCS Istituto Neurologico Carlo Besta (I.M., M.F., E.P., D.P.), Milan, Italy; Centre for Neuromuscular Diseases (M.L., M.M.R.), University College London, Queen Square; University College London Institute of Child Health & Great Ormond Street Hospital (T.B., F.M.), London, England; Translational Neurosciences (Pediatrics) (R.S.F.), St. Jude Children's Research Hospital, Memphis, TN; and Department of Neurology (J.E.S., K.J.E., D.N.H.), University of Rochester, NY.

Background And Objectives: This study examined the association between body mass index (BMI) and disability in children with Charcot-Marie-Tooth disease (CMT).

Methods: We conducted a cross-sectional analysis of 477 patients with CMT who were 3 to 20 years of age from the Inherited Neuropathy Consortium and 316 age- and sex-matched healthy children from the 1,000 Norms Project. BMI was categorized according to the International Obesity Task Force (IOTF) criteria, and BMI categorization was compared with healthy children. IOTF categories (adult equivalent BMI cut points) were severely underweight (BMI <17 kg/m), underweight (BMI ≥17-<18.5 kg/m), healthy weight (BMI ≥18.5-<25 kg/m), overweight (BMI ≥25-<30 kg/m), and obese (BMI ≥30 kg/m). Scores on the 0 to 44-point CMT Pediatric Scale (CMTPedS), a well-validated measure of disability, were examined in relation to BMI.

Results: There was a higher proportion of children with CMT categorized as severely underweight (5.7% vs 0.3%), underweight (10.3% vs 5.1%), and obese (7.3% vs 3.8%) ( < 0.05). Fewer children with CMT were categorized as healthy weight (61.8% vs 74.4%) ( < 0.05), and the proportion of overweight (14.9% vs 16.5%) between groups was similar. CMTPedS scores (mean ± SD) for weight categories were as follows: severely underweight 27 ± 9, underweight 20 ± 8, healthy weight 17 ± 9, overweight 17 ± 9, and obese 22 ± 10. Compared to children with a healthy weight with CMT, being severely underweight was associated with being more disabled ( < 0.001), as was being obese ( = 0.015).

Discussion: The proportion of children with CMT who are underweight or obese is higher compared to age- and sex-matched healthy children. In children with CMT, being underweight or obese is associated with greater disability, when compared to children with CMT of healthy weight.
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http://dx.doi.org/10.1212/WNL.0000000000012725DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8605613PMC
October 2021

Teaching NeuroImage: Basal Ganglia T1 Hyperintensity and SWI Signal Diabetic Striatopathy in an 18-Year-Old Man With Type 1 Diabetes Mellitus.

Neurology 2021 Nov 14;97(21):e2148-e2149. Epub 2021 Jul 14.

From the Department of Pediatrics, Division of Neurology, The Children's Hospital of Philadelphia, Philadelphia, PA.S. Yum is currently at the Perelman School of Medicine at the University of Pennsylvania.

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http://dx.doi.org/10.1212/WNL.0000000000012489DOI Listing
November 2021

Disease-modifying effects of edasalonexent, an NF-κB inhibitor, in young boys with Duchenne muscular dystrophy: Results of the MoveDMD phase 2 and open label extension trial.

Neuromuscul Disord 2021 05 4;31(5):385-396. Epub 2021 Feb 4.

Catabasis Pharmaceuticals, Inc., Boston, MA, United States.

Chronic activation of NF-κB is a key driver of muscle degeneration and suppression of muscle regeneration in Duchenne muscular dystrophy. Edasalonexent (CAT-1004) is an orally-administered novel small molecule that covalently links two bioactive compounds (salicylic acid and docosahexaenoic acid) that inhibit NF-κB. This placebo-controlled, proof-of-concept phase 2 study with open-label extension in boys ≥4-<8 years old with any dystrophin mutation examined the effect of edasalonexent (67 or 100 mg/kg/day) compared to placebo or off-treatment control. Endpoints were safety/tolerability, change from baseline in MRI T relaxation time of lower leg muscles and functional assessment, as well as pharmacodynamics and biomarkers. Treatment was well-tolerated and the majority of adverse events were mild, and most commonly of the gastrointestinal system (primarily diarrhea). There were no serious adverse events in the edasalonexent groups. Edasalonexent 100 mg/kg was associated with slowing of disease progression and preservation of muscle function compared to an off-treatment control period, with decrease in levels of NF-κB-regulated genes and improvements in biomarkers of muscle health and inflammation. These results support investigating edasalonexent in future trials and have informed the design of the edasalonexent phase 3 clinical trial in boys with Duchenne.
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http://dx.doi.org/10.1016/j.nmd.2021.02.001DOI Listing
May 2021

An ancestral 10-bp repeat expansion in VWA1 causes recessive hereditary motor neuropathy.

Brain 2021 03;144(2):584-600

Divisions of Neurology and Human Genetics, Children's Hospital of Philadelphia, Philadelphia, PA, USA.

The extracellular matrix comprises a network of macromolecules such as collagens, proteoglycans and glycoproteins. VWA1 (von Willebrand factor A domain containing 1) encodes a component of the extracellular matrix that interacts with perlecan/collagen VI, appears to be involved in stabilizing extracellular matrix structures, and demonstrates high expression levels in tibial nerve. Vwa1-deficient mice manifest with abnormal peripheral nerve structure/function; however, VWA1 variants have not previously been associated with human disease. By interrogating the genome sequences of 74 180 individuals from the 100K Genomes Project in combination with international gene-matching efforts and targeted sequencing, we identified 17 individuals from 15 families with an autosomal-recessive, non-length dependent, hereditary motor neuropathy and rare biallelic variants in VWA1. A single disease-associated allele p.(G25Rfs*74), a 10-bp repeat expansion, was observed in 14/15 families and was homozygous in 10/15. Given an allele frequency in European populations approaching 1/1000, the seven unrelated homozygote individuals ascertained from the 100K Genomes Project represents a substantial enrichment above expected. Haplotype analysis identified a shared 220 kb region suggesting that this founder mutation arose >7000 years ago. A wide age-range of patients (6-83 years) helped delineate the clinical phenotype over time. The commonest disease presentation in the cohort was an early-onset (mean 2.0 ± 1.4 years) non-length-dependent axonal hereditary motor neuropathy, confirmed on electrophysiology, which will have to be differentiated from other predominantly or pure motor neuropathies and neuronopathies. Because of slow disease progression, ambulation was largely preserved. Neurophysiology, muscle histopathology, and muscle MRI findings typically revealed clear neurogenic changes with single isolated cases displaying additional myopathic process. We speculate that a few findings of myopathic changes might be secondary to chronic denervation rather than indicating an additional myopathic disease process. Duplex reverse transcription polymerase chain reaction and immunoblotting using patient fibroblasts revealed that the founder allele results in partial nonsense mediated decay and an absence of detectable protein. CRISPR and morpholino vwa1 modelling in zebrafish demonstrated reductions in motor neuron axonal growth, synaptic formation in the skeletal muscles and locomotive behaviour. In summary, we estimate that biallelic variants in VWA1 may be responsible for up to 1% of unexplained hereditary motor neuropathy cases in Europeans. The detailed clinical characterization provided here will facilitate targeted testing on suitable patient cohorts. This novel disease gene may have previously evaded detection because of high GC content, consequential low coverage and computational difficulties associated with robustly detecting repeat-expansions. Reviewing previously unsolved exomes using lower QC filters may generate further diagnoses.
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http://dx.doi.org/10.1093/brain/awaa420DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8263055PMC
March 2021

Natural history of Charcot-Marie-Tooth disease type 2A: a large international multicentre study.

Brain 2020 12;143(12):3589-3602

Unit of Rare Neurodegenerative and Neurometabolic Diseases, Department of Clinical Neurosciences, Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy.

Mitofusin-2 (MFN2) is one of two ubiquitously expressed homologous proteins in eukaryote cells, playing a critical role in mitochondrial fusion. Mutations in MFN2 (most commonly autosomal dominant) cause Charcot-Marie-Tooth disease type 2A (CMT2A), the commonest axonal form of CMT, with significant allelic heterogeneity. Previous, moderately-sized, cross sectional genotype-phenotype studies of CMT2A have described the phenotypic spectrum of the disease, but longitudinal natural history studies are lacking. In this large multicentre prospective cohort study of 196 patients with dominant and autosomal recessive CMT2A, we present an in-depth genotype-phenotype study of the baseline characteristics of patients with CMT2A and longitudinal data (1-2 years) to describe the natural history. A childhood onset of autosomal dominant CMT2A is the most predictive marker of significant disease severity and is independent of the disease duration. When compared to adult onset autosomal dominant CMT2A, it is associated with significantly higher rates of use of ankle-foot orthoses, full-time use of wheelchair, dexterity difficulties and also has significantly higher CMT Examination Score (CMTESv2) and CMT Neuropathy Score (CMTNSv2) at initial assessment. Analysis of longitudinal data using the CMTESv2 and its Rasch-weighted counterpart, CMTESv2-R, show that over 1 year, the CMTESv2 increases significantly in autosomal dominant CMT2A (mean change 0.84 ± 2.42; two-tailed paired t-test P = 0.039). Furthermore, over 2 years both the CMTESv2 (mean change 0.97 ± 1.77; two-tailed paired t-test P = 0.003) and the CMTESv2-R (mean change 1.21 ± 2.52; two-tailed paired t-test P = 0.009) increase significantly with respective standardized response means of 0.55 and 0.48. In the paediatric CMT2A population (autosomal dominant and autosomal recessive CMT2A grouped together), the CMT Pediatric Scale increases significantly both over 1 year (mean change 2.24 ± 3.09; two-tailed paired t-test P = 0.009) and over 2 years (mean change 4.00 ± 3.79; two-tailed paired t-test P = 0.031) with respective standardized response means of 0.72 and 1.06. This cross-sectional and longitudinal study of the largest CMT2A cohort reported to date provides guidance for variant interpretation, informs prognosis and also provides natural history data that will guide clinical trial design.
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http://dx.doi.org/10.1093/brain/awaa323DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7805791PMC
December 2020

Refining clinical trial inclusion criteria to optimize the standardized response mean of the CMTPedS.

Ann Clin Transl Neurol 2020 09 6;7(9):1713-1715. Epub 2020 Aug 6.

School of Health Sciences, University of Sydney, The Children's Hospital at Westmead, Sydney, New South Wales, Australia.

The CMT Pediatric Scale (CMTPedS) is a reliable, valid, and responsive clinical outcome measure of disability in children with CMT. The aim of this study was to identify the most responsive patient subset(s), based on the standardized response mean (SRM), to optimize the CMTPedS as a primary outcome measure for upcoming clinical trials. Analysis was based on a 2-year natural history data from 187 children aged 3-20 years with a range of CMT genetic subtypes. Subsets based on age (3-8 years), disability level (CMTPedS score 0-14), and CMT type (CMT1A) increased the SRM of the CMTPedS considerably. Refining the inclusion criteria in clinical trials to younger, mildly affected cases of CMT1A optimizes the responsiveness of the CMTPedS.
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http://dx.doi.org/10.1002/acn3.51145DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7480902PMC
September 2020

Team Approach: Management of Brachial Plexus Birth Injury.

JBJS Rev 2020 07;8(7):e1900200

Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.

Brachial plexus birth injury is an upper-extremity paralysis that occurs from a traction injury to the brachial plexus during birth. Approximately 10% to 30% of children with a brachial plexus birth injury have residual neurologic deficits with associated impact on upper-limb function. Management of brachial plexus birth injuries with a multidisciplinary team allows optimization of functional recovery while avoiding unnecessary intervention. Early occupational therapy should be initiated with a focus on range of motion and motor learning. The need for microsurgical reconstruction of the brachial plexus can be predicted based on early physical examination findings, and reconstruction is generally performed at 3 to 9 months of age. The majority of children with residual neurologic deficits develop associated glenohumeral dysplasia. These children may require secondary procedures, including botulinum toxin injection, subscapularis and pectoralis lengthening, shoulder capsular release, shoulder tendon transfer, and humeral osteotomy.
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http://dx.doi.org/10.2106/JBJS.RVW.19.00200DOI Listing
July 2020

Clinical Course in a Patient With Spinal Muscular Atrophy Type 0 Treated With Nusinersen and Onasemnogene Abeparvovec.

J Child Neurol 2020 10 9;35(11):717-723. Epub 2020 Jun 9.

Division of Neurology, 367873Children's Hospital of Philadelphia, Philadelphia, PA, USA.

Spinal muscular atrophy type 0 is the most severe phenotype of the disease, with patients presenting with contractures, weakness, and respiratory failure at birth, and is typically fatal within weeks. We describe the case of a patient with spinal muscular atrophy type 0 who was treated with both nusinersen and onasemnogene abeparvovec. She has made modest motor improvements since treatment initiation with a 30-point improvement in CHOP-INTEND score, and continues to make motor gains at age 13 months without regression of function, although she remains profoundly weak. Although she has had motor improvements, she has also had continued systemic complications from her spinal muscular atrophy, including chronic respiratory failure, dysphagia, congenital heart malformation, digit necrosis, and diffuse macular rash. This case highlights the challenges in treating those with more severe disease phenotypes and raises questions of how some systemic complications may respond to current SMN replacement therapies.
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http://dx.doi.org/10.1177/0883073820928784DOI Listing
October 2020

Improving Temporomandibular Range of Motion in People With Duchenne Muscular Dystrophy and Spinal Muscular Atrophy.

Am J Occup Ther 2020 Mar/Apr;74(2):7402205080p1-7402205080p10

Sabrina W. Yum, MD, is Attending Physician, Neurology Department, Children's Hospital of Philadelphia, Philadelphia, PA, and Assistant Professor of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia.

Importance: People with Duchenne muscular dystrophy (DMD) and spinal muscular atrophy (SMA) develop impaired oral function because of reduced temporomandibular joint range of motion (ROM), which affects feeding and oral hygiene activities of daily living (ADLs).

Objective: To assess whether the TheraBite, an intraoral stretching device, improves ROM.

Design: Case series, with intervention duration varying from 7 to 30 mo. Treatment frequency varied from weekly to consultative (several times per year).

Setting: Varied depending on the ease of transportation for the participant and caregivers. Two participants were treated in an outpatient medical clinic. The other was provided consultative care during multidisciplinary medical clinics and completed a home program.

Participants: Two adults with DMD and one with SMA.

Intervention: Stretching protocol using the TheraBite.

Outcomes And Measures: Temporomandibular active ROM (AROM) was determined using a disposable TheraBite oral goniometer. Passive ROM (PROM) was determined using the adhesive scale on the TheraBite. Measures were taken at baseline, each intervention or consultation, and the end of care. ADL participation and caregiver burden were measured at the end of intervention.

Results: For participants with DMD, AROM remained unchanged, but PROM increased by 40%-65%. The participant with SMA demonstrated 33% and 47% improvements in AROM and PROM, respectively. Participants or caregivers reported improved feeding function, improved oral hygiene, or reduced fatigue.

Conclusion: TheraBite may improve temporomandibular PROM in people with DMD and temporomandibular AROM and PROM in people with SMA. It may also improve ADL function and consequently reduce caregiver burden. Further investigation is warranted.

What This Article Adds: Temporomandibular contracture in people with DMD and SMA contributes to reduced lifespan and loss of function. Use of the TheraBite with this population may preserve temporomandibular ROM and improve feeding, hygiene, and quality-of-life outcomes.
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http://dx.doi.org/10.5014/ajot.2020.030825DOI Listing
June 2020

A longitudinal study of CMT1A using Rasch analysis based CMT neuropathy and examination scores.

Neurology 2020 03 11;94(9):e884-e896. Epub 2020 Feb 11.

From the Department of Neurology (V.F., S.S., S.A.K.), University of Colorado Denver, Aurora; Department of Neurology (G.A.), Connecticut Children's Medical Center, Hartford; Department of Neurology (C.B., S.F., T.G., L.G., R.R.S., J.W., M.E.S.), University of Iowa Hospitals and Clinics, Iowa City; Health Informatics Institute (K.D., C.A.K.), University of South Florida, Tampa; University of Sydney and The Children's Hospital at Westmead (J.B.), New South Wales, Australia; Department of Neurology (J.D., C.E.S.), Stanford University, CA; Department of Neurology (S.F., J.L., S.R., R.R.S. , M.E.S.), Wayne State University, Detroit, MI; Department of Neurology (R.S.F.), Nemours Children's Hospital, Orlando, FL; Department of Neurology (D.N.H.), University of Rochester, NY; MRC Centre for Neuromuscular Diseases (M.L., M.M.R.), UCL Queen Square Institute of Neurology, London, UK; Department of Neurology (R.A.L.), Cedars-Sinai Medical Center, Los Angeles, CA; Department of Neurology (J.L.), Vanderbilt University, Nashville, TN; Departments of Neurology and Neuroscience (T.E.L., C.J.S.), John Hopkins University School of Medicine, Baltimore, MD; Department of Child Neurology (I.M., E.P.) and Department of Clinical Neurosciences (C.P., G.P.,* D.P.), Fondazione IRCCS Istituto Neurologico Carlo Besta, Milan, Italy; Istituti Clinici Scientifici Maugeri (G.P.*), Neurorehabilitation Unit, Scientific Institute of Telese Terme (BN), Italy; Department of Neurology (F.M.), UCL Institute of Child Health and Great Ormond Street Hospital, London, UK; Department of Neurology (S.R.), University of Michigan, Ann Arbor; PRA Health Sciences (S.R.), Raleigh, NC; Department of Neurology (M.S.) and Department of Human Genetics and Hussman Institute for Human Genomics (S.Z.), University of Miami Miller School of Medicine, FL; Department of Neurology (R.S.), Massachusetts General Hospital, Boston; Department of Neurology (D.W.), University of Minnesota, Minneapolis; Department of Neurology (S.W.Y., S.S.S.), Hospital of the University of Pennsylvania, Philadelphia; and Department of Neurology (S.W.Y.), Children's Hospital of Philadelphia, PA.

Objective: To evaluate the sensitivity of Rasch analysis-based, weighted Charcot-Marie-Tooth Neuropathy and Examination Scores (CMTNS-R and CMTES-R) to clinical progression in patients with Charcot-Marie-Tooth disease type 1A (CMT1A).

Methods: Patients with CMT1A from 18 sites of the Inherited Neuropathies Consortium were evaluated between 2009 and 2018. Weighted CMTNS and CMTES modified category responses were developed with Rasch analysis of the standard scores. Change from baseline for CMTNS-R and CMTES-R was estimated with longitudinal regression models.

Results: Baseline CMTNS-R and CMTES-R scores were available for 517 and 1,177 participants, respectively. Mean ± SD age of participants with available CMTES-R scores was 41 ± 18 (range 4-87) years, and 56% were female. Follow-up CMTES-R assessments at 1, 2, and 3 years were available for 377, 321, and 244 patients. A mixed regression model showed significant change in CMTES-R score at years 2 through 6 compared to baseline (mean change from baseline 0.59 points at 2 years, = 0.0004, n = 321). Compared to the original CMTES, the CMTES-R revealed a 55% improvement in the standardized response mean (mean change/SD change) at 2 years (0.17 vs 0.11). Change in CMTES-R at 2 years was greatest in mildly to moderately affected patients (1.48-point mean change, 95% confidence interval 0.99-1.97, < 0.0001, for baseline CMTES-R score 0-9).

Conclusion: The CMTES-R demonstrates change over time in patients with CMT1A and is more sensitive than the original CMTES. The CMTES-R was most sensitive to change in patients with mild to moderate baseline disease severity and failed to capture progression in patients with severe CMT1A.

Clinicaltrialsgov Identifier: NCT01193075.
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http://dx.doi.org/10.1212/WNL.0000000000009035DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7238948PMC
March 2020

A multidisciplinary approach to dosing nusinersen for spinal muscular atrophy.

Neurol Clin Pract 2019 Oct;9(5):424-432

Division of Neurology (CDZ), Department of Pediatrics, University of Florida, Gainesville; Department of Neurology (CDZ, JB, SWY, EAK), University of Pennsylvania; Division of Neurology (CDZ, JB, SWY, EAK), Children's Hospital of Philadelphia; and Department of Anesthesiology (EB, AAH, SD), Department of Physical Therapy (AMG), and Department of Pulmonology (OM), Children's Hospital of Philadelphia, PA.

Background: In December 2016, nusinersen gained FDA approval as the first pharmacologic treatment for spinal muscular atrophy (SMA), a disorder of motor neurons and the leading genetic cause of infant mortality. Nusinersen's intrathecal delivery requirement, strict dosage protocol, and accelerated FDA approval presented a challenge to health care centers hoping to implement treatment of patients with SMA. Scheduling logistics, combined with the specific ventilatory, anesthetic, and spinal access needs of this patient population, requires extensive coordination of care. This complexity, in addition to the high cost of treatment, may lead to overburdening of an institution's dosing resources, causing delays in treatment initiation and limiting patients' access to therapy and may result in barriers to coverage.

Methods: We initiated a comprehensive stepwise protocol to maximize patient inclusion, as well as safety and efficiency outcome measures. This retrospective cohort study reviews the dosing process.

Results: As a result of immense collaborative efforts involving care coordination of patients and families, in addition to health providers in the divisions of neurology, anesthesiology, pulmonology, orthopedics, interventional radiology, physical therapy, and neurosurgery, we have successfully dosed 62 SMA patients. Throughout this process, we have improved anesthetic techniques, as well as minimized procedural complications and missed scheduled doses.

Conclusion: We present here recommendations for safe and effective implementation of nusinersen utilizing a multidisciplinary approach, based on our 1 and a half year experience at a tertiary care children's hospital.
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http://dx.doi.org/10.1212/CPJ.0000000000000718DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6814423PMC
October 2019

Disruption of cardiac thin filament assembly arising from a mutation in : A novel mechanism of neonatal dilated cardiomyopathy.

Sci Adv 2019 09 4;5(9):eaax2066. Epub 2019 Sep 4.

Department of Cellular and Molecular Medicine and Sarver Molecular Cardiovascular Research Program, The University of Arizona, Tucson, AZ, USA.

Neonatal heart failure is a rare, poorly-understood presentation of familial dilated cardiomyopathy (DCM). Exome sequencing in a neonate with severe DCM revealed a homozygous nonsense variant in leiomodin 2 (, p.Trp398*). Leiomodins (Lmods) are actin-binding proteins that regulate actin filament assembly. While disease-causing mutations in smooth () and skeletal () muscle isoforms have been described, the cardiac () isoform has not been previously associated with human disease. Like our patient, -null mice have severe early-onset DCM and die before weaning. The infant's explanted heart showed extraordinarily short thin filaments with isolated cardiomyocytes displaying a large reduction in maximum calcium-activated force production. The lack of extracardiac symptoms in -null mice, and remarkable morphological and functional similarities between the patient and mouse model informed the decision to pursue cardiac transplantation in the patient. To our knowledge, this is the first report of aberrant cardiac thin filament assembly associated with human cardiomyopathy.
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http://dx.doi.org/10.1126/sciadv.aax2066DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6726455PMC
September 2019

Mortality and respiratory support in X-linked myotubular myopathy: a RECENSUS retrospective analysis.

Arch Dis Child 2020 04 4;105(4):332-338. Epub 2019 Sep 4.

Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts, USA

Purpose: Individuals with X-linked myotubular myopathy (XLMTM) who survive infancy require extensive supportive care, including ventilator assistance, wheelchairs and feeding tubes. Half die before 18 months of age. We explored respiratory support and associated mortality risk in RECENSUS, particularly among patients ≤5 years old who received respiratory support at birth; this subgroup closely matches patients in the ASPIRO trial of gene therapy for XLMTM.

Design: RECENSUS is an international, retrospective study of patients with XLMTM. Descriptive and time-to-event analyses examined survival on the basis of age, respiratory support, tracheostomy use, predicted mutational effects and life-sustaining care.

Results: Outcomes for 145 patients were evaluated. Among 126 patients with respiratory support at birth, mortality was 47% overall and 59% among those ≤5 years old. Median survival time was shorter for patients ≤5 years old than for those >5 years old (2.2 years (IQR 0.7-5.6) vs 30.2 years (IQR 19.4-30.2)). The most common cause of death was respiratory failure (66.7%). Median survival time was longer for patients with a tracheostomy than for those without (22.8 years (IQR 8.7-30.2) vs 1.8 years (IQR 0.2-not estimable)). The proportion of patients living without a tracheostomy was 50% at age 6 months and 28% at age 2 years. Median survival time was longer with provision of life-sustaining care than without (19.4 years (IQR 3.1-not estimable) vs 0.2 years (IQR 0.1-2.1)).

Conclusions: High mortality, principally due to respiratory failure, among patients with XLMTM ≤5 years old despite respiratory support underscores the need for early diagnosis, informed decision-making and disease-modifying therapies.

Trial Registration Number: NCT02231697.
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http://dx.doi.org/10.1136/archdischild-2019-317910DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7054136PMC
April 2020

Balance impairment in pediatric charcot-marie-tooth disease.

Muscle Nerve 2019 09 15;60(3):242-249. Epub 2019 May 15.

Children's Hospital of Philadelphia, Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA.

Introduction: Balance impairment contributes to gait dysfunction, falls, and reduced quality of life in adults with Charcot-Marie-Tooth disease (CMT) but has been minimally examined in pediatric CMT.

Methods: The CMT Pediatric Scale (CMTPedS) was administered to 520 children with CMT. Associations between balance function (Bruininks-Oseretsky Test of Motor Proficiency [BOT-2]) and sensorimotor and gait impairments were investigated.

Results: Daily trips/falls were reported by 42.3% of participants. Balance (BOT-2) varied by CMT subtype, was impaired in 42% of 4-year-olds, and declined with age (P < 0.001). Vibration (P < 0.001), pinprick (P < 0.004), ankle dorsiflexion strength (P < 0.001), and foot alignment (P < 0.004) were associated with BOT-2 balance (adjusted R = 0.28). The visual dependence of balance increased with age.

Discussion: Balance impairment occurs from a young age in children with CMT. Balance intervention studies are required in pediatric CMT and should consider the degree of sensorimotor impairment, foot malalignment, and visual dependence. Muscle Nerve, 2019.
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http://dx.doi.org/10.1002/mus.26500DOI Listing
September 2019

Modifier Gene Candidates in Charcot-Marie-Tooth Disease Type 1A: A Case-Only Genome-Wide Association Study.

J Neuromuscul Dis 2019 ;6(2):201-211

Department for Human Genetics and Hussman Institute for Human Genomics, University of Miami, Miami, FL, USA.

Background: Charcot-Marie-Tooth disease type 1A (CMT1A) is caused by a uniform 1.5-Mb duplication on chromosome 17p, which includes the PMP22 gene. Patients often present the classic neuropathy phenotype, but also with high clinical variability.

Objective: We aimed to identify genetic variants that are potentially associated with specific clinical outcomes in CMT1A.

Methods: We genotyped over 600,000 genomic markers using DNA samples from 971 CMT1A patients and performed a case-only genome-wide association study (GWAS) to identify potential genetic association in a subset of 644 individuals of European ancestry. A total of 14 clinical outcomes were analyzed in this study.

Results: The analyses yielded suggestive association signals in four clinical outcomes: difficulty with eating utensils (lead SNP rs4713376, chr6 : 30773314, P = 9.91×10-7, odds ratio = 3.288), hearing loss (lead SNP rs7720606, chr5 : 126551732, P = 2.08×10-7, odds ratio = 3.439), decreased ability to feel (lead SNP rs17629990, chr4 : 171224046, P = 1.63×10-7, odds ratio = 0.336), and CMT neuropathy score (lead SNP rs12137595, chr1 : 4094068, P = 1.14×10-7, beta = 3.014).

Conclusions: While the results require validation in future genetic and functional studies, the detected association signals may point to novel genetic modifiers in CMT1A.
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http://dx.doi.org/10.3233/JND-190377DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6597974PMC
December 2019

Thoracoscopic thymectomy for juvenile myasthenia gravis.

Pediatr Surg Int 2019 May 7;35(5):603-610. Epub 2019 Feb 7.

Division of Pediatric General, Thoracic and Fetal Surgery, Children's Hospital of Philadelphia, 34th Street and Civic Center Boulevard, Philadelphia, PA, 19104, USA.

Purpose: A randomized controlled trial of thymectomy in myasthenia gravis demonstrated improved clinical outcomes in adults, but data surrounding juvenile cases, especially those treated with minimally invasive approaches, are limited. Here, we review our experience with thoracoscopic thymectomy for juvenile myasthenia gravis (JMG) in the largest cohort to date.

Methods: All cases of thymectomy for JMG in a single tertiary referral center between 2007 and 2018 were reviewed (N = 50). Patients underwent left thoracoscopic approach with extended dissection and without use of monopolar energy. Demographics, diagnostic criteria, and clinical classification, as well as surgical data were collected. Clinical status and medications were reviewed in follow-up.

Results: The mean age at surgery was 10.5 ± 0.8 years. Ocular disease and generalized disease each comprised half of the cohort. No patients suffered complications or increased risk of morbidity or mortality with thymectomy. At any interval of follow-up through 3.5 years, 49.8% of patients were improved compared to their pre-operative presentation, and there was a significant trend towards decreased steroid use.

Conclusion: Thoracoscopic thymectomy is a safe treatment for juvenile myasthenia gravis in pediatric patients over a wide range of ages, body masses, and symptoms. Our experience adds evidence that pediatric patients likely benefit from thymectomy with improved clinical status and reduced medications.
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http://dx.doi.org/10.1007/s00383-019-04441-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6456483PMC
May 2019

Variation in SIPA1L2 is correlated with phenotype modification in Charcot- Marie- Tooth disease type 1A.

Ann Neurol 2019 03;85(3):316-330

Department for Human Genetics and Hussman Institute for Human Genomics, University of Miami, Miami, FL.

Objective: Genetic modifiers in rare disease have long been suspected to contribute to the considerable variance in disease expression, including Charcot-Marie-Tooth disease type 1A (CMT1A). To address this question, the Inherited Neuropathy Consortium collected a large standardized sample of such rare CMT1A patients over a period of 8 years. CMT1A is caused in most patients by a uniformly sized 1.5 Mb duplication event involving the gene PMP22.

Methods: We genotyped DNA samples from 971 CMT1A patients on Illumina BeadChips. Genome-wide analysis was performed in a subset of 330 of these patients, who expressed the extremes of a hallmark symptom: mild and severe foot dorsiflexion strength impairment. SIPA1L2 (signal-induced proliferation-associated 1 like 2), the top identified candidate modifier gene, was expressed in the peripheral nerve, and our functional studies identified and confirmed interacting proteins using coimmunoprecipitation analysis, mass spectrometry, and immunocytochemistry. Chromatin immunoprecipitation and in vitro siRNA experiments were used to analyze gene regulation.

Results: We identified significant association of 4 single nucleotide polymorphisms (rs10910527, rs7536385, rs4649265, rs1547740) in SIPA1L2 with foot dorsiflexion strength (p < 1 × 10 ). Coimmunoprecipitation and mass spectroscopy studies identified β-actin and MYH9 as SIPA1L2 binding partners. Furthermore, we show that SIPA1L2 is part of a myelination-associated coexpressed network regulated by the master transcription factor SOX10. Importantly, in vitro knockdown of SIPA1L2 in Schwannoma cells led to a significant reduction of PMP22 expression, hinting at a potential strategy for drug development.

Interpretation: SIPA1L2 is a potential genetic modifier of CMT1A phenotypic expressions and offers a new pathway to therapeutic interventions. ANN NEUROL 2019;85:316-330.
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http://dx.doi.org/10.1002/ana.25426DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7263419PMC
March 2019

Development and validation of the Charcot-Marie-Tooth Disease Infant Scale.

Brain 2018 12;141(12):3319-3330

Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, Thailand.

Many genetic subtypes of Charcot-Marie-Tooth disease (CMT) show signs of symptomatic disease during the earliest years of life. This might be the ideal time to intervene before progression of clinical sequelae due to demyelination and axonal loss. In the absence of disease-specific clinical trial outcome measures for CMT during infancy and early childhood the aim of this study was to develop and validate a functional measure of disease severity, known as the Charcot-Marie-Tooth disease Infant Scale (CMTInfS). Development projects involved identification of a preliminary pool of 31 items representing the range of disability in affected patients aged 0-4 years from a systematic review of the literature, peer review by 12 expert clinicians and researchers in the field, design of a scoring algorithm and pilot testing in 22 participants. Subsequently, a series of validation projects were conducted based on 128 assessments of: 26 confirmed cases of inherited neuropathy (17 CMT1A, one CMT1B, one CMT1D, one CMT2C, one CMT2S, two CMT4C, one CMTX3, one Riboflavin Transporter Deficiency Type 2, and one unidentified mutation); seven 'at risk' cases and 95 unaffected healthy controls recruited through the NIH-funded Inherited Neuropathies Consortium. Validation projects included: Item, Factor and Rasch analysis, intra- and inter-rater reliability, discriminant ability and convergent validity with the CMT Pediatric Scale (CMTPedS) for children aged 3-4 years. Development and validation projects produced a psychometrically robust 15-item scale. Rasch analysis supported the viability of the CMTInfS as a unidimensional measure of disease severity and showed good overall model fit, no evidence of misfitting items or persons and was well targeted for affected children. The CMTInfS demonstrated high intra-rater reliability [intraclass correlation coefficient (ICC)3,1 0.999, 95% confidence interval 0.996-1.000) and inter-rater reliability (ICC2,1 0.997, 95% confidence interval 0.992-0.999). The CMTInfS was able to discriminate between the CMT group and controls (P = 0.006), and convergent validity demonstrated good agreement between CMTInfS and CMTPedS scores (r = 0.76, P = 0.01). The final version of the CMTInfS requires 20 min to administer and is a reliable and sensitive functional outcome measure for early onset CMT and related neuropathies.10.1093/brain/awy280_video1awy280media15970672819001.
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http://dx.doi.org/10.1093/brain/awy280DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6312041PMC
December 2018

βIV Spectrinopathies Cause Profound Intellectual Disability, Congenital Hypotonia, and Motor Axonal Neuropathy.

Am J Hum Genet 2018 06 31;102(6):1158-1168. Epub 2018 May 31.

Department of Neuroscience and Integrative Molecular and Biomedical Sciences Graduate Program, Baylor College of Medicine, Houston, TX 77030, USA. Electronic address:

βIV spectrin links ankyrinG (AnkG) and clustered ion channels at axon initial segments (AISs) and nodes of Ranvier to the axonal cytoskeleton. Here, we report bi-allelic pathogenic SPTBN4 variants (three homozygous and two compound heterozygous) that cause a severe neurological syndrome that includes congenital hypotonia, intellectual disability, and motor axonal and auditory neuropathy. We introduced these variants into βIV spectrin, expressed these in neurons, and found that 5/7 were loss-of-function variants disrupting AIS localization or abolishing phosphoinositide binding. Nerve biopsies from an individual with a loss-of-function variant had reduced nodal Na channels and no nodal KCNQ2 K channels. Modeling the disease in mice revealed that although ankyrinR (AnkR) and βI spectrin can cluster Na channels and partially compensate for the loss of AnkG and βIV spectrin at nodes of Ranvier, AnkR and βI spectrin cannot cluster KCNQ2- and KCNQ3-subunit-containing K channels. Our findings define a class of spectrinopathies and reveal the molecular pathologies causing nervous-system dysfunction.
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http://dx.doi.org/10.1016/j.ajhg.2018.04.012DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5992132PMC
June 2018

Use of the Wilmington Robotic Exoskeleton to Improve Upper Extremity Function in Patients With Duchenne Muscular Dystrophy.

Am J Occup Ther 2018 Mar/Apr;72(2):7202345010p1-7202345010p5

Sabrina W. Yum, MD, is Pediatric Neurologist, Neurology Department, Children's Hospital of Philadelphia, PA, and Assistant Professor of Clinical Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia.

Patients with Duchenne muscular dystrophy in their second decade of life present with decreased upper extremity strength and active range of motion (AROM) that limit activities of daily living (ADLs). We evaluated the ability of the Wilmington Robotic Exoskeleton (WREX) to improve AROM and independence with ADLs. A retrospective chart review of 9 patients who trialed the WREX was performed. Patients were classified on the basis of the Brooke Upper Extremity Scale. AROM, strength, and independence with ADLs were assessed before and after a WREX trial. Patients demonstrated increased shoulder flexion and abduction (25°-100°, median = 55°) and elbow flexion (10°-110°, median = 60°). Increased independence with self-feeding, item retrieval, use of phones and tablets, and facial grooming were noted. The WREX allowed for gravity-reduced movement via elastic bands to unweight the upper extremity, enabling increased upper extremity active movement that supported increased independence with ADLs.
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http://dx.doi.org/10.5014/ajot.2018.022939DOI Listing
February 2018

Homozygous boricua TBCK mutation causes neurodegeneration and aberrant autophagy.

Ann Neurol 2018 01;83(1):153-165

Neuromuscular and Neurogenetic Disorders of Childhood Section, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD.

Objective: Autosomal-recessive mutations in TBCK cause intellectual disability of variable severity. Although the physiological function of TBCK remains unclear, loss-of-function mutations are associated with inhibition of mechanistic target of rapamycin complex 1 (mTORC1) signaling. Given that mTORC1 signaling is known to regulate autophagy, we hypothesized that TBCK-encephalopathy patients with a neurodegenerative course have defects in autophagic-lysosomal dysfunction.

Methods: Children (n = 8) of Puerto Rican (Boricua) descent affected with homozygous TBCK p.R126X mutations underwent extensive neurological phenotyping and neurophysiological studies. We quantified autophagosome content in TBCK patient-derived fibroblasts by immunostaining and assayed autophagic markers by western assay. Free sialylated oligosaccharide profiles were assayed in patient's urine and fibroblasts.

Results: The neurological phenotype of children with TBCK p.R126X mutations, which we call TBCK-encephaloneuronopathy (TBCKE), include congenital hypotonia, progressive motor neuronopathy, leukoencephalopathy, and epilepsy. Systemic features include coarse facies, dyslipidemia, and osteoporosis. TBCK fibroblasts in vitro exhibit increased numbers of LC3 autophagosomes and increased autophagic flux by immunoblots. Free oligosaccharide profiles in fibroblasts and urine of TBCKE patients differ from control fibroblasts and are ameliorated by treatment with the mTORC1 activator leucine.

Interpretation: TBCKE is a clinically distinguishable syndrome with progressive central and peripheral nervous system dysfunction, consistently observed in patients with the p.R126X mutation. We provide evidence that inappropriate autophagy in the absence of cellular stressors may play a role in this disorder, and that mTORC1 activation may ameliorate the autophagic-lysosomal system dysfunction. Free oligosaccharide profiles could serve as a novel biomarker for this disorder as well as a tool to evaluate potential therapeutic interventions. Ann Neurol 2018;83:153-165.
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http://dx.doi.org/10.1002/ana.25130DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5876123PMC
January 2018

A multicenter, retrospective medical record review of X-linked myotubular myopathy: The recensus study.

Muscle Nerve 2018 04 22;57(4):550-560. Epub 2017 Dec 22.

Audentes Therapeutics, San Francisco, California, USA.

Introduction: X-linked myotubular myopathy (XLMTM), characterized by severe hypotonia, weakness, respiratory distress, and early mortality, is rare and natural history studies are few.

Methods: RECENSUS is a multicenter chart review of male XLMTM patients characterizing disease burden and unmet medical needs. Data were collected between September 2014 and June 2016.

Results: Analysis included 112 patients at six clinical sites. Most recent patient age recorded was ≤18 months for 40 patients and >18 months for 72 patients. Mean (SD) age at diagnosis was 3.7 (3.7) months and 54.3 (77.1) months, respectively. Mortality was 44% (64% ≤18 months; 32% >18 months). Premature delivery occurred in 34/110 (31%) births. Nearly all patients (90%) required respiratory support at birth. In the first year of life, patients underwent an average of 3.7 surgeries and spent 35% of the year in the hospital.

Discussion: XLMTM is associated with high mortality, disease burden, and healthcare utilization. Muscle Nerve 57: 550-560, 2018.
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http://dx.doi.org/10.1002/mus.26018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5900738PMC
April 2018

Natural history of Charcot-Marie-Tooth disease during childhood.

Ann Neurol 2017 Sep;82(3):353-359

The University of Sydney, Sydney Children's Hospitals Network (Randwick and Westmead, Sydney, New South Wales, Australia.

Objective: To determine the rate of disease progression in a longitudinal natural history study of children with Charcot-Marie-Tooth (CMT) disease.

Methods: Two hundred six (103 female) participants aged 3 to 20 years enrolled in the Inherited Neuropathies Consortium were assessed at baseline and 2 years. Demographic, anthropometric, and diagnostic information were collected. Disease progression was assessed with the CMT Pediatric Scale (CMTPedS), a reliable Rasch-built linearly weighted disability scale evaluating fine and gross motor function, strength, sensation, and balance.

Results: On average, CMTPedS Total scores progressed at a rate of 2.4 ± 4.9 over 2 years (14% change from baseline; p < 0.001). There was no difference between males and females (mean difference, 0.5; 95% confidence interval [CI], -0.9 to 1.9; p = 0.49). The most responsive CMTPedS items were dorsiflexion strength (z-score change, -0.3; 95% CI, -0.6 to -0.05; p = 0.02), balance (z-score change, -1.0; 95% CI, -1.9 to -0.09; p = 0.03), and long jump (z-score change, -0.4; 95% CI, -0.7 to -0.02; p = 0.04). Of the most common genetic subtypes, 111 participants with CMT1A/PMP22 duplication progressed by 1.8 ± 4.2 (12% change from baseline; p < 0.001), 9 participants with CMT1B/MPZ mutation progressed by 2.2 ± 5.1 (11% change), 6 participants with CMT2A/MFN2 mutation progressed by 6.2 ± 7.9 (23% change), and 7 participants with CMT4C/SH3TC2 mutations progressed by 3.0 ± 4.5 (12% change). Participants with CMT2A progressed faster than CMT1A (mean difference, -4.4; 95% CI, -8.1 to -0.8; p = 0.02). Children with CMT1A progressed consistently through early childhood (3-10 years) and adolescence (11-20 years; mean difference, 1.1; 95% CI, -0.6 to 2.7; p = 0.19), whereas CMT2A appeared to progress faster during early childhood than adolescence (mean difference, 10.0; 95% CI, -2.2 to 22.2; p = 0.08).

Interpretation: Using the CMTPedS as an outcome measure of disease severity, children with CMT progress at a significant rate over 2 years. Understanding the rate at which children with CMT deteriorate is essential for adequately powering trials of disease-modifying interventions. Ann Neurol 2017;82:353-359.
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http://dx.doi.org/10.1002/ana.25009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8294172PMC
September 2017

Cross-sectional analysis of a large cohort with X-linked Charcot-Marie-Tooth disease (CMTX1).

Neurology 2017 Aug 2;89(9):927-935. Epub 2017 Aug 2.

From the Department of Neurology (F.B.P., D.N.H.), University of Rochester Medical Center, NY; MRC Centre for Neuromuscular Diseases (M.L., A.M.R., M.M.R.), UCL Institute of Neurology, UK; Department of Neurology (C.P., D.P.), Carlo Besta Neurological Institute, Milan, Italy; Department of Neurosciences (G.P.), Institute of Telese Terme (BN), Italy; Children's Hospital at Westmead (J.B.), University of Sydney, Australia; Department of Neurology (J.L.), Vanderbilt University, Nashville, TN; Neuromuscular Program (S.W.Y.), Children's Hospital of Philadelphia, PA; Department of Neurology (R.A.L.), Cedars-Sinai Medical Center, Los Angeles, CA; Department of Neurology (J.D.), Stanford University, CA; Institute of Genetic Medicine (R.H.), Newcastle University, UK; Department of Neurology (M.E.S.), University of Iowa Hospitals and Clinics; and Department of Neurology (S.S.S.), University of Pennsylvania, Philadelphia.

Objective: To extend the phenotypic description of Charcot-Marie-Tooth disease (CMTX1) and to draw new genotype-phenotype relationships.

Methods: Mutations in cause the main X-linked form of CMTX (CMTX1). We report cross-sectional data from 160 patients (from 120 different families, with 89 different mutations) seen at the Inherited Neuropathies Consortium centers.

Results: We evaluated 87 males who had a mean age of 41 years (range 10-78 years) and 73 females who had a mean age of 46 years (range 15-84 years). Sensory-motor polyneuropathy affects both sexes, more severely in males than in females, and there was a strong correlation between age and disease burden in males but not in females. Compared with females, males had more severe reduction in motor and sensory neurophysiology parameters. In contrast to females, the radial nerve sensory response in older males tended to be more severely affected compared with younger males. Median and ulnar nerve motor amplitudes were also more severely affected in older males, whereas ulnar nerve motor potentials tended to be more affected in older females. Conversely, there were no statistical differences between the sexes in other features of the disease, such as problems with balance and hand dexterity.

Conclusions: In the absence of a phenotypic correlation with specific mutations, sex-specific distinctions and clinically relevant attributes need to be incorporated into the measurements for clinical trials in people with CMTX1.

Clinicaltrialsgov Identifier: NCT01193075.
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http://dx.doi.org/10.1212/WNL.0000000000004296DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5577965PMC
August 2017

Phenotypic Variability of Childhood Charcot-Marie-Tooth Disease.

JAMA Neurol 2016 Jun;73(6):645-51

University of Sydney & Children's Hospital at Westmead, Sydney Australia.

Importance: Disease severity of childhood Charcot-Marie-Tooth disease (CMT) has not been extensively characterized, either within or between types of CMT to date.

Objective: To assess the variability of disease severity in a large cohort of children and adolescents with CMT.

Design, Setting, And Participants: A cross-sectional study was conducted among 520 children and adolescents aged 3 to 20 years at 8 universities and hospitals involved in the Inherited Neuropathies Consortium between August 6, 2009, and July 31, 2014, in Australia, Italy, the United Kingdom, and the United States. Data analysis was conducted from August 1, 2014, to December 1, 2015.

Main Outcomes And Measures: Scores on the Charcot-Marie-Tooth Disease Pediatric Scale (CMTPedS), a well-validated unidimensional clinical outcome measure to assess disease severity. This instrument includes 11 items assessing fine and gross motor function, sensation, and balance to produce a total score ranging from 0 (unaffected) to 44 (severely affected).

Results: Among the 520 participants (274 males) aged 3 to 20 years, CMT type 1A (CMT1A) was the most prevalent type (252 [48.5%]), followed by CMT2A (31 [6.0%]), CMT1B (15 [2.9%]), CMT4C (13 [2.5%]), and CMTX1 (10 [1.9%]). Disease severity ranged from 1 to 44 points on the CMTPedS (mean [SD], 21.5 [8.9]), with ankle dorsiflexion strength and functional hand dexterity test being most affected. Participants with CMT1B (mean [SD] CMTPedS score, 24.0 [7.4]), CMT2A (29.7 [7.1]), and CMT4C (29.8 [8.6]) were more severely affected than those with CMT1A (18.9 [7.7]) and CMTX1 (males: 15.3 [7.7]; females: 13.0 [3.6]) (P < .05). Scores on the CMTPedS tended to worsen principally during childhood (ages, 3-10 years) for participants with CMT4C and CMTX1 and predominantly during adolescence for those with CMT1B and CMT2A (ages, 11-20 years), while CMT1A worsened consistently throughout childhood and adolescence. For individual items, participants with CMT4C recorded more affected functional dexterity test scores than did those with all other types of CMT (P < .05). Participants with CMT1A and CMTX1 performed significantly better on the 9-hole peg test and balance test than did those with all other types of CMT (P < .05). Participants with CMT2A had the weakest grip strength (P < .05), while those with CMT2A and CMT4C exhibited the weakest ankle plantarflexion and dorsiflexion strength, as well as the lowest long jump and 6-minute walk test distances (P < .05). Multiple regression modeling identified increasing age (r = 0.356, β = 0.617, P < .001) height (r = 0.251, β = 0.309, P = .002), self-reported foot pain (r = 0.162, β = .114, P = .009), and self-reported hand weakness (r = 0.243, β = 0.203, P < .001) as independent predictors of disease severity.

Conclusions And Relevance: These results highlight the phenotypic variability within CMT genotypes and mutation-specific manifestations between types. This study has identified distinct functional limitations and self-reported impairments to target in future therapeutic trials.
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http://dx.doi.org/10.1001/jamaneurol.2016.0171DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4916861PMC
June 2016

De novo PMP2 mutations in families with type 1 Charcot-Marie-Tooth disease.

Brain 2016 06 23;139(Pt 6):1649-56. Epub 2016 Mar 23.

Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA

We performed whole exome sequencing on a patient with Charcot-Marie-Tooth disease type 1 and identified a de novo mutation in PMP2, the gene that encodes the myelin P2 protein. This mutation (p.Ile52Thr) was passed from the proband to his one affected son, and segregates with clinical and electrophysiological evidence of demyelinating neuropathy. We then screened a cohort of 136 European probands with uncharacterized genetic cause of Charcot-Marie-Tooth disease and identified another family with Charcot-Marie-Tooth disease type 1 that has a mutation affecting an adjacent amino acid (p.Thr51Pro), which segregates with disease. Our genetic and clinical findings in these kindred demonstrate that dominant PMP2 mutations cause Charcot-Marie-Tooth disease type 1.
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http://dx.doi.org/10.1093/brain/aww055DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5022672PMC
June 2016

A 6-Year-Old With Leg Cramps.

Pediatrics 2015 Oct 14;136(4):732-9. Epub 2015 Sep 14.

Departments of Pediatrics, and Anesthesiology and Critical Care Medicine, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania; and.

A 6-year-old girl presented with a history of leg pain and cramping that progressively worsened over a 2- to 3-week period of time. Her examination was notable for normal vital signs, limited range of motion of her left hip, and a limp. Inflammatory markers were slightly elevated, but the serum electrolytes, calcium, and magnesium, complete blood cell count and differential, and creatine kinase level were normal. She was hospitalized for further diagnostic evaluation and was noted to have abnormal muscle movements classified as myokymia (continuous involuntary quivering, rippling, or undulating movement of muscles). Electromyography confirmed the myokymia but did not reveal evidence of a myopathy or neuropathy, prompting additional evaluation for a systemic etiology.
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http://dx.doi.org/10.1542/peds.2015-0332DOI Listing
October 2015

Genotype-phenotype characteristics and baseline natural history of heritable neuropathies caused by mutations in the MPZ gene.

Brain 2015 Nov 25;138(Pt 11):3180-92. Epub 2015 Aug 25.

1 Department of Neurology, University of Iowa Hospitals and Clinics, Iowa, IA, USA.

We aimed to characterize genotype-phenotype correlations and establish baseline clinical data for peripheral neuropathies caused by mutations in the myelin protein zero (MPZ) gene. MPZ mutations are the second leading cause of Charcot-Marie-Tooth disease type 1. Recent research makes clinical trials for patients with MPZ mutations a realistic possibility. However, the clinical severity varies with different mutations and natural history data on progression is sparse. We present cross-sectional data to begin to define the phenotypic spectrum and clinical baseline of patients with these mutations. A cohort of patients with MPZ gene mutations was identified in 13 centres of the Inherited Neuropathies Consortium - Rare Disease Clinical Research Consortium (INC-RDCRC) between 2009 and 2012 and at Wayne State University between 1996 and 2009. Patient phenotypes were quantified by the Charcot-Marie-Tooth disease neuropathy score version 1 or 2 and the Charcot-Marie-Tooth disease paediatric scale outcome instruments. Genetic testing was performed in all patients and/or in first- or second-degree relatives to document mutation in MPZ gene indicating diagnosis of Charcot-Marie-Tooth disease type 1B. There were 103 patients from 71 families with 47 different MPZ mutations with a mean age of 40 years (range 3-84 years). Patients and mutations were separated into infantile, childhood and adult-onset groups. The infantile onset group had higher Charcot-Marie-Tooth disease neuropathy score version 1 or 2 and slower nerve conductions than the other groups, and severity increased with age. Twenty-three patients had no family history of Charcot-Marie-Tooth disease. Sixty-one patients wore foot/ankle orthoses, 19 required walking assistance or support, and 10 required wheelchairs. There was hearing loss in 21 and scoliosis in 17. Forty-two patients did not begin walking until after 15 months of age. Half of the infantile onset patients then required ambulation aids or wheelchairs for ambulation. Our results demonstrate that virtually all MPZ mutations are associated with specific phenotypes. Early onset (infantile and childhood) phenotypes likely represent developmentally impaired myelination, whereas the adult-onset phenotype reflects axonal degeneration without antecedent demyelination. Data from this cohort of patients will provide the baseline data necessary for clinical trials of patients with Charcot-Marie-Tooth disease caused by MPZ gene mutations.
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http://dx.doi.org/10.1093/brain/awv241DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4643641PMC
November 2015
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