Genetic Patterns of Selected Muscular Dystrophies in the Muscular Dystrophy Surveillance, Tracking, and Research Network.

Background and Objectives: To report the genetic etiologies of Emery-Dreifuss muscular dystrophy (EDMD), limb-girdle muscular dystrophy (LGMD), congenital muscular dystrophy (CMD), and distal muscular dystrophy (DD) in 6 geographically defined areas of the United States. Methods: This was a cross-sectional, population-based study in which we studied the genes and variants associated with muscular dystrophy in individuals who were diagnosed with and received care for EDMD, LGMD, CMD, and DD from January 1, 2008, through December 31, 2016, in the 6 areas of the United States covered by the Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet). Variants of unknown significance (VUSs) from the original genetic test reports were reanalyzed for changes in interpretation. Results: Among 243 individuals with definite or probable muscular dystrophy, LGMD was the most common diagnosis (138 cases), followed by CMD (62 cases), DD (22 cases), and EDMD (21 cases). There was a higher proportion of male individuals compared with female individuals, which persisted after excluding X-linked genes (EMD) and autosomal genes reported to have skewed gender ratios (ANO5, CAV3, and LMNA). The most common associated genes were FKRP, CAPN3, ANO5, and DYSF. Reanalysis yielded more definitive variant interpretations for 60 of 144 VUSs, with a mean interval between the original clinical genetic test of 8.11 years for all 144 VUSs and 8.62 years for the 60 reclassified variants. Ten individuals were found to have monoallelic pathogenic variants in genes known to be primarily recessive. Discussion: This study is distinct for being an examination of 4 types of muscular dystrophies in selected geographic areas of the United States. The striking proportion of resolved VUSs demonstrates the value of periodic re-examinations of these variants. Such re-examinations will resolve some genetic diagnostic ambiguities before initiating repeat testing or more invasive diagnostic procedures such as muscle biopsy. The presence of monoallelic pathogenic variants in recessive genes in our cohort indicates that some individuals with muscular dystrophy continue to face incomplete genetic diagnoses; further refinements in genetic knowledge and diagnostic approaches will optimize diagnostic information for these individuals.

Time to diagnosis of Duchenne muscular dystrophy remains unchanged: Findings from the Muscular Dystrophy Surveillance, Tracking, and Research Network, 2000-2015.

INTRODUCTION/AIMS: With current and anticipated disease-modifying treatments, including gene therapy, an early diagnosis for Duchenne muscular dystrophy (DMD) is crucial to assure maximum benefit. In 2009, a study from the Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet) showed an average diagnosis age of 5 years among males with DMD born from January 1, 1982 to December 31, 2000. Initiatives were implemented by the US Centers for Disease Control and Prevention (CDC) and patient organizations to reduce time to diagnosis. We conducted a follow-up study in a surveillance cohort born after January 1, 2000 to determine whether there has been an improvement in time to diagnosis. METHODS: We assessed the age of diagnosis among males with DMD born from January 1, 2000 to December 31, 2015 using data collected by six US MD STARnet surveillance sites (Colorado, Iowa, western New York State, the Piedmont region of North Carolina, South Carolina, and Utah). The analytic cohort included 221 males with definite or probable DMD diagnosis without a documented family history. We computed frequency count and percentage for categorical variables, and mean, median, and standard deviation (SD) for continuous variables. RESULTS: The mean [median] ages in years of diagnostic milestones were: first signs, 2.7 [2.0]; first creatine kinase (CK), 4.6 [4.6]; DNA/muscle biopsy testing, 4.9 [4.8]; and time from first signs to diagnostic confirmation, 2.2 [1.4]. DISCUSSION: The time interval between first signs of DMD and diagnosis remains unchanged at 2.2 years. This results in lost opportunities for timely genetic counseling, implementation of standards of care, initiation of glucocorticoids, and participation in clinical trials.

Differentiation of Pediatric-Onset Duchenne and Becker Muscular Dystrophy Subphenotypes Using Data from the Muscular Dystrophy Surveillance Tracking and Research Network (MD STARnet).

Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) phenotypes are used to describe disease progression in affected individuals. However, considerable heterogeneity has been observed across and within these two phenotypes, suggesting a spectrum of severity rather than distinct conditions. Characterizing the phenotypes and subphenotypes aids researchers in the design of clinical studies and clinicians in providing anticipatory guidance to affected individuals and their families. Using data from the Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet), we used K-means cluster analysis to group phenotypically similar males with pediatric-onset dystrophinopathy. We identified four dystrophinopathy clusters: Classical BMD, Classical DMD, late ambulatory DMD, and severe DMD. The clusters that we identified align with both 'classical' and 'non-classical' dystrophinopathy described in the literature. Individuals with dystrophinopathies have heterogenous clinical presentations that cluster into phenotypically similar groups. Use of clinically-derived phenotyping may provide a clearer understanding of disease trajectories, reduce variability in study results, and prevent exclusion of certain cohorts from analysis. Findings from studying subphenotypes may ultimately improve our ability to predict disease progression.

Characterization of individuals with selected muscular dystrophies from the expanded pilot of the Muscular Dystrophy Surveillance, Tracking and Research Network (MD STARnet) in the United States.

INTRODUCTION: Data on muscular dystrophies (MDs), a heterogeneous group of heritable diseases hallmarked by progressive muscle deterioration, are scarce. OBJECTIVE: We describe cross-sectional sociodemographic and clinical characteristics of individuals with congenital, distal, Emery-Dreifuss, facioscapulohumeral, limb-girdle, myotonic, or oculopharyngeal MD. METHODS: The study was conducted in four sites (Arizona, Colorado, Iowa, and 12 western New York counties) as a pilot expansion of the Muscular Dystrophy Surveillance, Tracking and Research Network, funded by the Centers for Disease Control and Prevention. MDs were detected in healthcare facilities and administrative data sources using International Classification of Disease codes. Our sample contains 1,723 individuals with a MD diagnosis and a healthcare encounter between January 1, 2007 and December 31, 2011. RESULTS AND CONCLUSIONS: Individuals were mostly non-Hispanic and white. Median ages ranged from 9.2 to 66.0 years. Most (98%) had health insurance. The proportion of individuals who were disabled or unable to work increased with age (range: 8.6-46.4%). People with limb-girdle MD aged ≥18 years were more likely to be nonambulatory (range: 24.5-44.7%). The percentages of individuals with documented clinical interventions during the surveillance period were low. The most common cause of death was respiratory causes (46.3-57.1%); an ICD-10 code for MD (G71.1 or G71.0) was reported for nearly one-half. Our findings show wide variability in sociodemographic and clinical characteristics across MDs.

Diagnostic Accuracy of Phenotype Classification in Duchenne and Becker Muscular Dystrophy Using Medical Record Data1.

Dystrophinopathies are caused by mutations in DMD resulting in progressive muscle weakness. They are historically divided into the more severe Duchenne (DMD) and milder Becker (BMD) muscular dystrophy phenotypes. Classification is important for research and clinical care. The purpose of this study was to describe a multi-variable approach to classifying cases from the Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet) and to assess the accuracy of the diagnostic classification scheme. We used age at loss of mobility, molecular testing results, and age at symptom onset to classify cases as having DMD or BMD and to assess sensitivity and specificity. Mobility status showed low sensitivity and high specificity for predicting DMD (65.5% and 99.3%, respectively) and BMD (62.8% and 97.7%, respectively) phenotypes. Molecular testing showed 90.9% sensitivity and 66.4% specificity for DMD; 76.3% sensitivity and 90.0% specificity for BMD. Age of onset predicted DMD with sensitivity of 73.9% and specificity of 69.0%; BMD had 99.7% specificity and 36.7% sensitivity. Mobility status, molecular test results, and age at symptom onset are important but inconsistent measures for accurately classifying individuals into DMD or BMD phenotypes. These results have implications for prognosis in newly diagnosed individuals and for classifying phenotype in clinical trials.

Evaluating Implementation of the Updated Care Considerations for Duchenne Muscular Dystrophy.

Care Considerations for Duchenne Muscular Dystrophy were published in 2010. However, little is known about the extent to which these considerations were implemented after publication. With this article, we provide direction on evaluating the uptake of the 2018 Duchenne Muscular Dystrophy Care Considerations. We identify key elements of care and present suggestions for their use in evaluation and research.

A Pilot Survey Study of Adherence to Care Considerations for Duchenne Muscular Dystrophy.

Introduction Care Considerations supported by the Centers for Disease Control and Prevention for the management of Duchenne muscular dystrophy were published in 2010, but there has been limited study of implementation in the United States. Methods A questionnaire collecting information about standard care practices and perceived barriers was piloted by 9 clinic directors of facilities within the Muscular Dystrophy Surveillance, Tracking and Research network. Results Six clinic directors completed the questionnaire; 1 adult-only clinic was excluded. Over 80% adherence was found for 30 of 55 recommendations examined. Greatest variability was for initiation of corticosteroids, bone health monitoring, type of pulmonary function testing, and psychosocial management. Barriers included unclear guidelines, inadequate time and funding, family-specific barriers and lack of empirical support for some recommendations. Discussion This pilot study showed implementation of the 2010 Care Considerations, except for recommendations based largely on expert consensus. Complete adherence requires more studies and active promotion.

Muscular Dystrophy Surveillance, Tracking, and Research Network pilot: Population-based surveillance of major muscular dystrophies at four U.S. sites, 2007-2011.

BACKGROUND: For 10 years, the Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet) conducted surveillance for Duchenne and Becker muscular dystrophy (DBMD). We piloted expanding surveillance to other MDs that vary in severity, onset, and sources of care. METHODS: Our retrospective surveillance included individuals diagnosed with one of nine eligible MDs before or during the study period (January 2007-December 2011), one or more health encounters, and residence in one of four U.S. sites (Arizona, Colorado, Iowa, or western New York) at any time within the study period. We developed case definitions, surveillance protocols, and software applications for medical record abstraction, clinical review, and data pooling. Potential cases were identified by International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes 359.0, 359.1, and 359.21 and International Classification of Diseases, Tenth Revision (ICD-10) codes G71.0 and G71.1. Descriptive statistics were compared by MD type. Percentage of MD cases identified by each ICD-9-CM code was calculated. RESULTS: Of 2,862 cases, 32.9% were myotonic, dystrophy 25.8% DBMD, 9.7% facioscapulohumeral MD, and 9.1% limb-girdle MD. Most cases were male (63.6%), non-Hispanic (59.8%), and White (80.2%). About, half of cases were genetically diagnosed in self (39.1%) or family (6.2%). About, half had a family history of MD (48.9%). The hereditary progressive MD code (359.1) was the most common code for identifying eligible cases. The myotonic code (359.21) identified 83.4% of eligible myotonic dystrophy cases (786/943). CONCLUSIONS: MD STARnet is the only multisite, population-based active surveillance system available for MD in the United States. Continuing our expanded surveillance will contribute important epidemiologic and health outcome information about several MDs.

Bone Health and Endocrine Care of Boys with Duchenne Muscular Dystrophy: Data from the MD STARnet.

BACKGROUND: Patients with Duchenne muscular dystrophy (DMD) are at high risk of endocrine and bone health complications resulting from the high glucocorticoid (GC) doses used to treat this condition. There are limited data characterizing the clinical management of these complications. OBJECTIVE: To determine the frequency of bone health screening, endocrinologist evaluation, and use of endocrine and bone health pharmacotherapy in the clinical care of males with DMD. METHODS: A population based cohort study using data from the Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet) was conducted. Clinical data was abstracted from the medical records of 683 males with DMD at five surveillance sites across the US. RESULTS: A DXA scan had been documented in 24% of cases; the percentage of cases with DXA varied across surveillance sites from 13% to 43%, p < 0.001. History of fracture and greater disease duration were associated with greater odds of having a DXA. Only 4.7% of cases had documentation of an endocrinologist evaluation. The frequency of documented endocrine and bone health pharmacotherapy use included calcium (42.8%), vitamin D (36.6%), bisphosphonates (13.3%), growth hormone (1.9%), testosterone (1.7%), insulin (1.2%), and metformin (0.3%)Conclusions:A low percentage of DMD males had record of DXA scan, endocrinologist evaluation, or treatment with endocrine or bone health pharmacotherapy. Endocrine and bone health care may represent an unmet need in the DMD population.

Implementation of Duchenne Muscular Dystrophy Care Considerations.

BACKGROUND: Duchenne muscular dystrophy (DMD) is an X-linked disorder characterized by progressive muscle weakness and multisystem involvement. Recent advances in management of individuals with DMD have prolonged survival. Lack of standardized care spurred an international collaboration to develop consensus-based care considerations for diagnosis and management. In this study, we evaluate adherence to considerations at selected sites. METHODS: We collaborated with the Muscular Dystrophy Surveillance, Tracking, and Research Network. Our sample included males with DMD and Becker muscular dystrophy <21 years as of December 31, 2010, with 1 health care encounter on or after January 1, 2012. We collected data from medical records on encounters occurring January 1, 2012, through December 31, 2014. Adherence was determined when frequency of visits or assessments were at or above recommendations for selected care considerations. RESULTS: Our analytic sample included 299 individuals, 7% of whom (20/299) were classified as childhood-onset Becker muscular dystrophy. Adherence for neuromuscular and respiratory clinician visits was 65% for the cohort; neuromuscular assessments and corticosteroid side effect monitoring measures ranged from 16% to 68%. Adherence was 83% for forced vital capacity and ≤58% for other respiratory diagnostics. Cardiologist assessments and echocardiograms were found for at least 84%. Transition planning for education or health care was documented for 31% of eligible males. CONCLUSIONS: Medical records data were used to identify areas in which practice aligns with the care considerations. However, there remains inconsistency across domains and insufficiency in critical areas. More research is needed to explain this variability and identify reliable methods to measure outcomes.

Health profile of a cohort of adults with Duchenne muscular dystrophy.

INTRODUCTION: As the Duchenne muscular dystrophy (DMD) population ages, it is essential that we understand the late-stage health profile and provide the appropriate care for this emerging population. METHODS: We undertook a descriptive study to document the health profile of a cohort of adults with DMD using data from the Muscular Dystrophy Surveillance Tracking and Research network (MD STARnet). Data included information collected from Arizona, Colorado, Iowa, Georgia, and 12 counties in western New York on individuals born since January 1982 and followed through December 2012. RESULTS: In 208 adults with DMD, the number of individuals (N) and median ages (years) at which certain critical milestones were crossed and interventions initiated were as follows: development of cardiomyopathy, N = 145 (16.7); initiation of non-invasive ventilation, N = 99 (18.0); gastrostomy, N = 47 (19.0); and death, N = 59 (21.8). DISCUSSION: These population-based data provide critical information about late-stage health profiles among adults with DMD for developing appropriate models of care. Muscle Nerve 58: 219-223, 2018.

Secondary Conditions Among Males With Duchenne or Becker Muscular Dystrophy.

Duchenne and Becker muscular dystrophy are X-linked neuromuscular disorders characterized by progressive muscle degeneration. Despite the involvement of multiple systems, secondary conditions among affected males have not been comprehensively described. Two hundred nine caregivers of affected males (aged 3-31 years) identified by the Muscular Dystrophy Surveillance, Tracking, and Research Network completed a mailed survey that included questions about secondary conditions impacting multiple body functions. The 5 most commonly reported conditions in males with Duchenne were cognitive deficits (38.4%), constipation (31.7%), anxiety (29.3%), depression (27.4%), and obesity (19.5%). Higher frequencies of anxiety, depression, and kidney stones were found among nonambulatory males compared to ambulatory males. Attention-deficit hyperactivity disorder (ADHD) was more common in ambulatory than nonambulatory males. These data support clinical care recommendations for monitoring of patients with Duchenne or Becker muscular dystrophy by a multidisciplinary team to prevent and treat conditions that may be secondary to the diagnosis.

Respiratory Care Received by Individuals With Duchenne Muscular Dystrophy From 2000 to 2011.

BACKGROUND: Duchenne muscular dystrophy (DMD) causes progressive respiratory muscle weakness and decline in function, which can go undetected without monitoring. DMD respiratory care guidelines recommend scheduled respiratory assessments and use of respiratory assist devices. To determine the extent of adherence to these guidelines, we evaluated respiratory assessments and interventions among males with DMD in the Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet) from 2000 to 2011. METHODS: MD STARnet is a population-based surveillance system that identifies all individuals born during or after 1982 residing in Arizona, Colorado, Georgia, Hawaii, Iowa, and western New York with Duchenne or Becker muscular dystrophy. We analyzed MD STARnet respiratory care data for non-ambulatory adolescent males (12-17 y old) and men (≥18 y old) with DMD, assessing whether: (1) pulmonary function was measured twice yearly; (2) awake and asleep hypoventilation testing was performed at least yearly; (3) home mechanical insufflation-exsufflation, noninvasive ventilation, and tracheostomy/ventilators were prescribed; and (4) pulmonologists provided evaluations. RESULTS: During 2000-2010, no more than 50% of both adolescents and men had their pulmonary function monitored twice yearly in any of the years; 67% or fewer were assessed for awake and sleep hypoventilation yearly. Although the use of mechanical insufflation-exsufflation and noninvasive ventilation is probably increasing, prior use of these devices did not prevent all tracheostomies, and at least 18 of 29 tracheostomies were performed due to acute respiratory illnesses. Fewer than 32% of adolescents and men had pulmonologist evaluations in 2010-2011. CONCLUSIONS: Since the 2004 publication of American Thoracic Society guidelines, there have been few changes in pulmonary clinical practice. Frequencies of respiratory assessments and assist device use among males with DMD were lower than recommended in clinical guidelines. Collaboration of respiratory therapists and pulmonologists with clinicians caring for individuals with DMD should be encouraged to ensure access to the full spectrum of in-patient and out-patient pulmonary interventions.

Age at onset of first signs or symptoms predicts age at loss of ambulation in Duchenne and Becker Muscular Dystrophy: Data from the MD STARnet.

PURPOSE: We investigated the prognostic utility of onset age at first signs and symptoms (SS) to predict onset age at loss of ambulation (LOA) for childhood-onset Duchenne and Becker Muscular Dystrophies (DBMD). METHODS: Our cohort comprised male cases with DBMD ascertained by the population-based Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet). Adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using Cox proportional hazards models for associations between onset ages of first SS and LOA. Covariates controlled for were corticosteroid use, family history of DBMD, birth year, race/ethnicity, and MD STARnet site. Onset age at first SS was considered as a continuous and as a categorical variable. RESULTS: A one-year increase in onset age at first SS was significantly associated with a 10% reduction in annual risk of LOA (HR = 0.90, CI = 0.87-0.94). Treating onset age at first SS as a categorical variable yielded a similar association (≥ 5 years: referent; ≥ 3 to < 5 years: HR = 1.36, CI = 1.02-1.81; 18 months to < 3 years: HR = 1.72, CI = 1.31-2.26; < 18 months: HR = 1.52, CI = 1.14-2.02). CONCLUSIONS: Earlier onset age at first SS is associated with earlier onset age at LOA and may have clinical utility in differentiating childhood-onset Duchenne and Becker muscular dystrophies.

Delayed diagnosis in duchenne muscular dystrophy: data from the Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet).

OBJECTIVE: To identify key factors for the delay in diagnosis of Duchenne muscular dystrophy (DMD) without known family history. STUDY DESIGN: The cohort comes from the Muscular Dystrophy Surveillance, Tracking, and Research Network (MD STARnet), a multistate, multiple-source, population-based surveillance system that identifies and gathers information on all cases of Duchenne and Becker muscular dystrophy born since 1982. We analyzed medical records of 453 Duchenne and Becker muscular dystrophy boys to document the time course and steps taken to reach a definitive diagnosis. RESULTS: Among 156 boys without known family history of DMD prior to birth, first signs or symptoms were noted at a mean age of 2.5 years. Concerns resulted in primary care provider evaluation of the child at a mean age of 3.6 years. Mean age at time of initial creatine kinase was 4.7 years. Mean age at definitive diagnosis of DMD was 4.9 years. CONCLUSIONS: There is a delay of about 2.5 years between onset of DMD symptoms and the time of definitive diagnosis, unchanged over the previous 2 decades. This delay results in lost opportunities for timely genetic counseling and initiation of corticosteroid treatment. We recommend checking creatine kinase early in the evaluation of boys with unexplained developmental delay.