Facioscapulohumeral Muscular Dystrophy Type Research Articles

First-trimester noninvasive prenatal diagnosis of seven facioscapulohumeral muscular dystrophy type 1 families using SNP-based amplicon sequencing: An earlier, rapid and safer way.

The study is to explore the feasibility and value of SNP-based noninvasive prenatal diagnosis (NIPD) for facioscapulohumeral muscular dystrophy type 1 (FSHD1) in early pregnancy weeks. We prospectively collected seven FSHD1 families, with an average gestational age of 8+6 . Among these seven couples, there were three affected FSHD1 mothers and four affected fathers. A multiplex-PCR panel comprising 402 amplicons was designed to selective enrich for highly heterozygous SNPs upstream of the DUX4 gene. Risk haplotype was constructed based on familial linkage analysis. Fetal genotypes were accurately inferred through relative haplotype dosage analysis using Bayes Factor. All tests were successfully completed in a single attempt, and no recombination events were detected. NIPD results were provided within a week, which is 4 weeks earlier than karyomapping and 7 weeks earlier than Bionano single-molecule optical mapping (BOM). Ultimately, five FSHD1 fetuses and two normal fetuses were successfully identified, with a 100% concordance rate with karyomapping and BOM. Therefore, SNP-based NIPD for FSHD1 was demonstrated to be feasible and accurate in early weeks of gestation, although the risk of recombination events cannot be completely eliminated. In the future, testing of more cases is still necessary to fully determine the clinical utility.

Genetic diagnosis of facioscapulohumeral muscular dystrophy type 1 using rare-variant linkage analysis and long-read genome sequencing

Facioscapulohumeral dystrophy type 1 (FSHD1) is a progressive, debilitating skeletal myopathy that requires a multimodal approach for complete molecular characterization of pathogenic genotypes. Here, we report genomic analyses of a family with suspected FSHD1. We first performed short-read genome sequencing, followed by parametric linkage analysis using rare variants to map the disease locus to a single 1.7 Mb interval on chromosome 4q35.2 with a logarithm of the odds score of 3.2. We then used ultra-long-read genome sequencing as a single molecular test to genotype a pathogenic FSHD allele containing a 4qA permissive haplotype and 5 KpnI repeat units at the D4Z4 locus. These results demonstrate that genome-wide rare variant–based linkage analysis is a powerful tool for mapping disease loci in families, and ultra-long-read genome sequencing is capable of genotyping pathogenic FSHD1 alleles.

Molecular Diagnosis of Facioscapulohumeral Muscular Dystrophy in Patients Clinically Suspected of FSHD Using Optical Genome Mapping.

Facioscapulohumeral muscular dystrophy (FSHD) represents the third most common muscular dystrophy in the general population and is characterized by progressive and often asymmetric muscle weakness of the face, upper extremities, arms, lower leg, and hip girdle. In FSHD type 1, contraction of the number of D4Z4 repeats to 1-10 on the chromosome 4-permissive allele (4qA) results in abnormal epigenetic derepression of the DUX4 gene in skeletal muscle. In FSHD type 2, epigenetic derepression of the DUX4 gene on the permissive allele (4qA) with normal-sized D4Z4 repeats (mostly 8-20) is caused by heterozygous pathogenic variants in chromatin modifier genes such as SMCHD1, DNMT3B, or LRIF1. We present validation of the optical genome mapping (OGM) platform for accurate mapping of the D4Z4 repeat size, followed by diagnostic testing of 547 cases with a suspected clinical diagnosis of FSHD and next-generation sequencing (NGS) of the SMCHD1 gene to identify cases with FSHD2. OGM with Bionano Genomics Saphyr and EnFocus FSHD analysis software was used to identify FSHD haplotypes and D4Z4 repeat number and compared with the gold standard of Southern blot-based diagnosis. A custom Agilent SureSelect enrichment kit was used to enrich SMCHD1, followed by NGS on an Illumina system with 100-bp paired-end reads. Copy number variants were assessed using NxClinical software. We performed OGM for the diagnosis of FSHD in 547 patients suspected of FSHD between December 2019 and December 2022, including 301 male (55%) and 246 female patients (45%). Overall, 308 of the referred patients were positive for D4Z4 contraction on a permissive haplotype, resulting in a diagnosis of FSHD1. A total of 252 of 547 patients were referred for concurrent testing for FSHD1 and FSHD2. This resulted in the identification of FSHD2 in 9/252 (3.6%) patients. In our FSHD2 cohort, the 4qA allele size ranged from 8 to 18 repeats. Among FSHD1-positive cases, 2 patients had biallelic contraction and 4 patients had homozygous contraction and showed early onset of clinical features. Nine of the 308 patients (3%) positive for 4qA contraction had mosaic 4q alleles with contraction on at least one 4qA allele. The overall diagnostic yield in our cohort was 58%. A combination of OGM to identify the FSHD haplotype and D4Z4 repeat number and NGS to identify sequence and copy number variants in the SMCHD1 gene is a practical and cost-effective option with increased precision for accurate diagnosis of FSHD types 1 and 2.

Apabetalone, a Clinical-Stage, Selective BET Inhibitor, Opposes DUX4 Target Gene Expression in Primary Human FSHD Muscle Cells.

Facioscapulohumeral dystrophy (FSHD) is a muscle disease caused by inappropriate expression of the double homeobox 4 (DUX4) gene in skeletal muscle, and its downstream activation of pro-apoptotic transcriptional programs. Inhibitors of DUX4 expression have the potential to treat FSHD. Apabetalone is a clinical-stage bromodomain and extra-terminal (BET) inhibitor, selective for the second bromodomain on BET proteins. Using primary human skeletal muscle cells from FSHD type 1 patients, we evaluated apabetalone for its ability to counter DUX4's deleterious effects and compared it with the pan-BET inhibitor JQ1, and the p38 MAPK inhibitor-and DUX4 transcriptional repressor-losmapimod. We applied RNA-sequencing and bioinformatic analysis to detect treatment-associated impacts on the transcriptome of these cells. Apabetalone inhibited the expression of DUX4 downstream markers, reversing hallmarks of FSHD gene expression in differentiated muscle cells. JQ1, but not apabetalone, was found to induce apoptosis. While both BET inhibitors modestly impacted differentiation marker expression, they did not affect myotube fusion. Losmapimod also reduced expression of DUX4 target genes but differed in its impact on FSHD-associated pathways. These findings demonstrate that apabetalone inhibits DUX4 target gene expression and reverses transcriptional programs that contribute to FSHD pathology, making this drug a promising candidate therapeutic for FSHD.

Late-onset facioscapulohumeral muscular dystrophy type 1 in previously undiagnosed families: Presenting clinical features in an often-misdiagnosed disorder.

In our experience, patients with late-onset facioscapulohumeral muscular dystrophy type 1 (FSHD1) are frequently misdiagnosed, some for many years. The aim of this report is to document this clinical experience including the presenting symptoms and misdiagnoses and to discuss the challenges in diagnosing patients with late-onset FSHD1. We performed a retrospective medical record review and recorded clinical data on patients with a genetically confirmed diagnosis of FSHD1, who began to have symptoms at 50 years of age or older, and either had no family history of FSHD1 or had a history of an undiagnosed weakness in a family member. Thirteen patients, 7 men and 6 women, met the study inclusion criteria. Age of onset ranged from 52 to 74 (mean, 59.8) years, age of diagnosis ranged from 54 to 80 (mean, 66.5) years, and duration of symptoms from onset to diagnosis was 1 to 15 (mean, 6.7) years. Prior diagnoses included lumbosacral polyradiculopathy in five (38%); statin-related myopathy in two (15%); and one each of polymyositis, inclusion-body myositis, distal myopathy, limb-girdle muscular dystrophy, unspecific myopathy, and unspecified scapular winging. For eight patients (62%), family history was suspected in deceased members or if by confirmed DNA test postdiagnosis. The diagnosis of late-onset FSHD1 is often delayed by many years with patients frequently receiving misdiagnoses. FSHD1 may not be considered in the differential diagnosis of late-onset weakness due to its rarity and because its clinical features are subtler, nonspecific, and mimic other neuromuscular disorders.

Comparison of quantitative muscle ultrasound and whole-body muscle MRI in facioscapulohumeral muscular dystrophy type 1 patients

IntroductionMuscle ultrasound is a fast, non-invasive and cost-effective examination that can identify structural muscular changes by assessing muscle thickness and echointensity (EI) with a quantitative analysis (QMUS). To assess applicability and repeatability of QMUS, we evaluated patients with genetically confirmed facioscapulohumeral muscular dystrophy type 1 (FSHD1), comparing their muscle ultrasound characteristics with healthy controls and with those detected by MRI. We also evaluated relationships between QMUS and demographic and clinical characteristics.Materials and methodsThirteen patients were included in the study. Clinical assessment included MRC sum score, FSHD score and The Comprehensive Clinical Evaluation Form (CCEF). QMUS was performed with a linear transducer scanning bilaterally pectoralis major, deltoid, rectus femoris, tibialis anterior and semimembranosus muscles in patients and healthy subjects. For each muscle, we acquired three images, which were analysed calculating muscle EI by computer-assisted grey-scale analysis. QMUS analysis was compared with semiquantitative 1.5 T muscle MRI scale.ResultsAll muscles in FSHD patients showed a significant increased echogenicity compared to the homologous muscles in healthy subjects. Older subjects and patients with higher FSHD score presented increased muscle EI. Tibialis anterior MRC showed a significant inverse correlation with EI. Higher median EI was found in muscles with more severe MRI fat replacement.ConclusionsQMUS allows quantitative evaluation of muscle echogenicity, displaying a tight correlation with muscular alterations, clinical and MRI data. Although a confirmation on larger sample is needed, our research suggests a possible future application of QMUS in diagnosis and management of muscular disorders.

Association of 4qA-Specific Distal D4Z4 Hypomethylation With Disease Severity and Progression in Facioscapulohumeral Muscular Dystrophy.

To examine whether the regional methylation levels at the most distal D4Z4 repeat units (RU) in the 4qA-permissive haplotype were associated with disease severity and progression in facioscapulohumeral muscular dystrophy type 1 (FSHD1). This was a 21-year, retrospective, and observational cohort study conducted at the Fujian Neuromedical Centre (FNMC) in China. Methylation levels of the most distal D4Z4 RU, including 10 CpGs, were assessed in all participants by bisulfite sequencing. FSHD1 patients were stratified into 4 groups based on methylation percentage quartiles, including LM1 (low methylation), LM2 (low to intermediate methylation), LM3 (intermediate to high methylation), and highest methylation levels (HM). Patients received evaluations of motor function focusing on lower extremity (LE) progression at baseline and in follow-ups. FSHD clinical score (CS), age-corrected clinical severity scale (ACSS), and modified Rankin Scale were used to assess motor function. The methylation levels of the 10 CpGs were significantly lower in all 823 genetically confirmed FSHD1 patients than in 341 healthy controls (HCs). CpG6 methylation levels could distinguish: 1) FSHD1 patients from HCs; 2) symptomatic from asymptomatic/unaffected patients; 3) patients with LE involvement from those without LE involvement, with AUCs (95% CI) of 0.9684 (0.9584-0.9785), 0.7417 (0.6903-0.7931), and 0.6386 (0.5816-0.6956), respectively. CpG6 methylation levels were negatively correlated with both CS (r = -0.392) and ACSS (r = -0.432), and positively correlated with onset age of first-ever muscle weakness (r = 0.297). For the LM1, LM2, LM3, and HM groups, the respective proportions of LE involvement were 52.9%, 44.2%, 36.9%, and 23.4%; and onset ages of LE involvement were 20, 26.5, 25, and 26.5 years. Cox regression analysis-adjusted for sex, age at examination, D4Z4 RU, and 4qA/B haplotype-showed that the LM1, LM2, and LM3 groups (i.e., groups with lower methylation levels) had a higher risk for independent ambulation loss, with HRs (95% CI) of 3.523 (1.565-7.930), 3.356 (1.458-7.727), and 2.956 (1.245-7.020), respectively. 4q35 distal D4Z4 hypomethylation is correlated with disease severity and progression to lower extremity involvement.

Teaching Neuro Images : Coats disease revealing facioscapulohumeral muscular dystrophy

A 21-year-old Brazilian woman presented with mild facial muscle weakness, scapular winging and an asymmetric shoulder girdle, and peroneal weakness. Medical history disclosed mildly symptomatic Coats disease (CD) (figure). Muscle MRI studies were highly suggestive of facioscapulohumeral muscular dystrophy type 1 (FSHD1) (figure) and genetic testing confirmed this diagnosis.

P480: Validation of optical genome mapping as a laboratory-developed diagnostic test for facioscapulohumeral muscular dystrophy type 1

P480: Validation of optical genome mapping as a laboratory-developed diagnostic test for facioscapulohumeral muscular dystrophy type 1

A feasibility study of noninvasive prenatal diagnosis in facioscapulohumeral muscular dystrophy type 1 in a Chinese family.

Objective: To demonstrate the feasibility of haplotype-based noninvasive prenatal diagnosis of Facioscapulohumeral Muscular Dystrophy type 1 (FSHD1). Methods: Bionano optical mapping was used to identify the D4Z4 structural variation of the genomic DNA sample from the proband affected with FSHD1. In addition, based on the technique of next generation sequencing, the pathogenic haplotype was determined by using trio strategy through genotyping his parents, and also fetal inheritance of paternal haplotypes was then deduced using the Hidden Markov Model. Results: Bionano optical mapping analysis revealed that the proband has only three D4Z4 repeats left in the 4q35 chromosomal region and a disease-permitting 4qA haplotype. The other normal allele of the proband contains 29 D4Z4 repeats and also a 4qA haplotype. The noninvasive cell-free fetal DNA (cffDNA)-based haplotype analysis suggested that the fetus inherited the pathogenic allele from his father and thus was predicted to be affected by FSHD1. In addition, Bionano optical mapping also demonstrated the presence of the pathogenic allele in the fetus by interrogating the genomic DNA from the amniotic fluid cells. Conclusion: Our study showed the cffDNA-based haplotyping was feasible for the noninvasive prenatal diagnosis of FSHD1, which is able to provide earlier testing results with a lower risk of miscarriage and infection than invasive techniques.

Spotlight on the August 30 Issue

![Graphic][1]</img>#### Notable in Neurology This Week This issue features an article that examines the association between sex, menopause, and white matter hyperintensities; another determines optimal surveillance strategies for unruptured intracranial aneurysm growth. A featured article examines the association of healthy lifestyles with risk of Alzheimer disease and related dementias in low-income Black and White Americans. ### Quantitative Muscle Analysis in FSHD Using Whole-Body Fat-Referenced MRI: Composite Scores for Longitudinal and Cross-sectional Analysis This prospective, observational, multicenter study in patients with facioscapulohumeral muscular dystrophy (FSHD) type 1 demonstrated … [1]: /embed/inline-graphic-1.gif

Overview of Neuromuscular Disorder Molecular Diagnostic Experience for the Population of Latvia

Genetic testing has become an integral part of health care, allowing the confirmation of thousands of hereditary diseases, including neuromuscular disorders (NMDs). The reported average prevalence of individual inherited NMDs is 3.7-4.99 per 10,000. This number varies greatly in the selected populations after applying population-wide studies. The aim of this study was to evaluate the effect of genetic analysis as the first-tier test in patients with NMD and to calculate the disease prevalence and allelic frequencies for reoccurring genetic variants. Patients with NMD from Latvia with molecular tests confirming their diagnosis in 2008-2020 were included in this retrospective study. Diagnosis was confirmed in 153 unique cases of all persons tested. Next-generation sequencing resulted in a detection rate of 37%. Two of the most common childhood-onset NMDs in our population were spinal muscular atrophy and dystrophinopathies, with a birth prevalence of 1.01 per 10,000 newborns and 2.08 per 10,000 (male newborn population), respectively. The calculated point prevalence was 0.079 per 10,000 for facioscapulohumeral muscular dystrophy type 1, 0.078 per 10,000 for limb-girdle muscular dystrophy, 0.073 per 10,000 for nondystrophic congenital myotonia, 0.052 per 10,000 for spinobulbar muscular atrophy, and 0.047 per 10,000 for type 1 myotonic dystrophy. DNA diagnostics is a successful approach. The carrier frequencies of the common CAPN3, FKRP, SPG11, and HINT1 gene variants as well as that of the SMN1 gene exon 7 deletion in the population of Latvia are comparable with data from Europe. The carrier frequency of the CLCN1 gene variant c.2680C>T p.(Arg894Ter) is 2.11%, and consequently, congenital myotonia is the most frequent NMD in our population.

Serum miRNAs as biomarkers for the rare types of muscular dystrophy

Muscular dystrophies are a group of disorders that cause progressive muscle weakness. There is an increasing interest for the development of biomarkers for these disorders and specifically for Duchene Muscular Dystrophy. Limited research however, has been performed on the biomarkers’ development for the most rare muscular dystrophies, like the Facioscapulohumeral Muscular Dystrophy, Limb-Girdle Muscular Dystrophy and Myotonic Dystrophy type 2. Here, we aimed to identify novel serum-based miRNA biomarkers for these rare muscular dystrophies, through high-throughput next-generation RNA sequencing. We identified many miRNAs that associate with muscular dystrophy patients compared to controls. Based on a series of selection criteria, the two best candidate miRNAs for each of these disorders were chosen and validated in a larger number of patients. Our results showed that miR-223-3p and miR-206 are promising serum-based biomarkers for Facioscapulohumeral Muscular Dystrophy type 1, miR-143-3p and miR-486-3p for Limb-Girdle Muscular Dystrophy type 2A whereas miR-363-3p and miR-25-3p associate with Myotonic Dystrophy type 2. Some of the identified miRNAs were significantly elevated in the serum of the patients compared to controls, whereas some others were lower. In conclusion, we provide new evidence that certain circulating miRNAs may be used as biomarkers for three types of rare muscular dystrophies.

EP357: Molecular diagnosis of Facioscapulohumeral Muscular Dystrophy (FSHD) using optical genome mapping

Facioscapulohumeral muscular dystrophy (FSHD) is characterized by progressive and often asymmetric muscle weakness of the face, scapular stabilizers, shoulders, arms, lower leg, and hip girdle. Around 20% of patients are wheelchair-bound, and some also present with sensory, cardiac or neurological manifestations. The age of onset is variable and ranges from infancy to adult. There are two different forms of FSHD, FSHD type 1, and FSHD type 2. FSHD1 is most common, found in 95% of individuals diagnosed with FSHD, and the remaining 5% are diagnosed with FSHD2.

Cross-sectional Neuromuscular Phenotyping Study of Patients With Arhinia With SMCHD1 Variants.

Facioscapulohumeral muscular dystrophy type 2 (FSHD2) and arhinia are 2 distinct disorders caused by pathogenic variants in the same gene: SMCHD1. The mechanism underlying this phenotypic divergence remains unclear. In this study, we characterize the neuromuscular phenotype of individuals with arhinia caused by SMCHD1 variants and analyze their complex genetic and epigenetic criteria to assess their risk for FSHD2. Eleven individuals with congenital nasal anomalies, including arhinia, nasal hypoplasia, or anosmia, underwent a neuromuscular examination, genetic testing, muscle ultrasound, and muscle MRI. Risk for FSHD2 was determined by combined genetic and epigenetic analysis of 4q35 haplotype, D4Z4 repeat length, and methylation profile. We also compared expression levels of pathogenic DUX4 mRNA in primary myoblasts or dermal fibroblasts (upon myogenic differentiation or epigenetic transdifferentiation, respectively) in these individuals vs those with confirmed FSHD2. Among the 11 individuals with rare, pathogenic, heterozygous missense variants in exons 3-11 of SMCHD1, only a subset (n = 3/11; 1 male, 2 female; age 25-51 years) met the strict genetic and epigenetic criteria for FSHD2 (D4Z4 repeat unit length <21 in cis with a 4qA haplotype and D4Z4 methylation <30%). None of the 3 individuals had typical clinical manifestations or muscle imaging findings consistent with FSHD2. However, the patients with arhinia meeting the permissive genetic and epigenetic criteria for FSHD2 displayed some DUX4 expression in dermal fibroblasts under the epigenetic de-repression by drug treatment and in the primary myoblasts undergoing myogenic differentiation. In this cross-sectional study, we identified patients with arhinia who meet the full genetic and epigenetic criteria for FSHD2 and display the molecular hallmark of FSHD-DUX4 de-repression and expression in vitro-but who do not manifest with the typical clinicopathologic phenotype of FSHD2. The distinct dichotomy between FSHD2 and arhinia phenotypes despite an otherwise poised DUX4 locus implies the presence of novel disease-modifying factors that seem to operate as a switch, resulting in one phenotype and not the other. Identification and further understanding of these disease-modifying factors will provide valuable insight with therapeutic implications for both diseases.

Reprogramming of adult human peripheral blood mononuclear cells into hiPSCs from two patients with facioscapulohumeral muscular dystrophy type 1

Facioscapulohumeral muscular dystrophy (FSHD) is one of the most common muscular dystrophy. FSHD type 1 (FSHD1) is caused by multicopy contraction of D4Z4 repeats on chromosome 4q35. Human induced pluripotent stem cell (hiPSC) lines serve as important research models for various types of diseases in vitro. Here, we reprogrammed human peripheral blood mononuclear cells (PMBCs) into hiPSCs with episomal plasmid from two FSHD1 patients. These hiPSC lines maintained normal karyotype and exhibited typical morphology. Both of them could express pluripotency markers and differentiate into three layers. The hiPSC lines could be used for screening potential therapeutic targets and mechanism research.

Care for capabilities: Implementing the capability approach in rehabilitation of patients with neuromuscular diseases. Study protocol of the controlled before-after ReCap-NMD study.

High quality care of patients with neuromuscular diseases requires a personalised approach that focuses on achieving and maintaining a level of functioning that enables them to be in a state of well-being. The capability approach states that well-being should be understood in terms of capabilities, the substantial opportunities that people have to be and do things they have reasons to value. In this Rehabilitation and Capability care for patients with Neuromuscular diseases (ReCap-NMD) study, we want to investigate whether providing care based on the capability approach (capability care) has an added value in the rehabilitation of patients with neuromuscular diseases (NMD). Two groups of 30 adult patients with facioscapulohumeral muscular dystrophy or myotonic dystrophy type 1 will be included. The first group will receive rehabilitation care as usual with a follow-up period of 6 months. Then, based on theory, and experiences of patients and healthcare professionals, capability care will be developed. During the following 3 months, the multidisciplinary outpatient rehabilitation care team will be trained in providing this newly developed capability care. Subsequently, the second group will receive capability care, with a follow-up period of 6 months. A mixed methods approach is used with both qualitative and quantitative outcome measures to evaluate the effect of capability care and to perform a process evaluation. The primary outcome measure will be the Canadian Occupational Performance Measure. The ReCap-NMD study is the first study to design and implement a healthcare intervention based on the capability approach. The results of this study will expand our knowledge on how the capability approach can be applied in delivering and evaluating healthcare, and will show whether implementing such an intervention leads to a higher well-being for patients with NMD. Registered at Trialregister.nl (Trial NL8946) on 12th of October, 2020.

Prevalence and disease progression of genetically-confirmed facioscapulohumeral muscular dystrophy type 1 (FSHD1) in China between 2001 and 2020: a nationwide population-based study

SummaryBackgroundFacioscapulohumeral muscular dystrophy type 1 (FSHD1) is a rare disease, which is often underdiagnosed due to its heterogeneous presentations and complex molecular genetic basis, leading to a lack of population-based epidemiology data, especially of prevalence and disease progression.MethodsFujian Neuromedical Centre (FNMC) is a diagnosis centre for clinical-genetic FSHD in China, and the only one employing pulsed-field gel electrophoresis (PFGE)-based Southern blotting for all FSHD1 genetic tests. Three sources distributed across all six spatial zones in China, were used to obtain information regarding FSHD1 events, namely, FNMC, Genetic and Myopathy Group (branches of the Neurology Society of the Chinese Medical Association), and “FSHD-China” (an organization supported by FSHD patients). During 2001-2020, all genetically-confirmed FSHD1 from China were registered in FNMC. Follow-up was conducted in the 20-year period to obtain data on disease progression, which was mainly described in terms of independent ambulation loss.FindingsOf the 1,744 FSHD1 genetic tests (total test number 1,802) included in the analysis, 997 (57.2%) patients from 620 families were diagnosed with FSHD1. The estimated prevalence of genetically-confirmed FSHD1 in China is 0.75 per million (95% confidence interval [CI], 0.70-0.79) during 2001-2020, with 0.78 (95% CI, 0.72-0.85) in males and 0.71 (95% CI, 0.65-0.78) in females. The estimated prevalence increased from 0.22 (95% CI, 0.19-0.26) per million in 2001-2015 to 0.53 (95% CI, 0.49-0.57) per million in 2016-2020 (p < 0.001). The prevalence in Fujian province was 7.10 per million, 4.66 per million, and 2.44 per million, during 2001-2020, 2001-2015, and 2016-2020, respectively. Among the 861 symptomatic plus asymptomatic patients of the total 997 patients, the median onset age at first-ever muscle weakness was 16 years of age (range 1-81); the median number of contracted D4Z4 repeats was 5 units (range 1-9); the median 4qA-allele-specific methylation level was 41% (range 14%-69%). Of the 977 symptomatic patients followed-up during 2001-2020, 117 patients (12.0%) lost independent ambulation. The expected duration from onset of first-ever muscle weakness to onset of independent ambulation loss was 40 years. The group with loss of independent ambulation had a smaller number of contracted D4Z4 repeats (p < 0.001) and had an earlier onset age of first-ever muscle weakness (p < 0.001) compared to the group without loss of independent ambulation.InterpretationOur research captures the largest genetically-confirmed FSHD1 population worldwide, to calculate its prevalence of 0.75 per million in China from 2001 to 2020. Approximately 12.0% of symptomatic plus asymptomatic patients of FSHD1 will lose independent ambulation in 40 years from onset of first-ever muscle weakness.FundingThis work has been supported by the grants (U2005201, 81870902, N.W.) and (81974193, 81671237, Z.Q.W.) from the National Natural Science Foundation of China; Joint Funds for the Innovation of Science and Technology of Fujian Province (2018Y9082) (N.W.), and the Key Clinical Specialty Discipline Construction Program of Fujian (N.W.).

RESPONSE TO LETTER TO THE EDITOR "AUDITORY DYSFUNCTION IN FACIOSCAPULOHUMERAL MUSCULAR DYSTROPHY TYPE 1: BEYOND THE INNER EAR INVOLVEMENT" BY GHELLER ET AL.

In Reply: We read with interest the Letter to the Editor entitled “Auditory dysfunction in Facioscapulohumeral Muscular Dystrophy Type 1: beyond the inner ear involvement” by Gheller et al. (1), reporting further evidence of an auditory impairment in patients affected by Facioscapulohumeral Muscular Dystrophy Type 1 (FSHD1). In particular, Gheller et al. performed various audiological examinations, including speech evaluation tests, frequency discrimination and event related potential (P300) latency analysis, highlighting the presence of a hearing impairment in a population of 13 patients affected by FSHD1, for frequencies higher than 2 kHz. In our recent study on 26 FSHD1 patients, we reported a general alteration of otoacoustic emissions (OAEs) analysis, irrespective of the degree of muscular involvement, suggesting a primary cochlear dysfunction as a typical feature of this disease (2). Altogether, these findings further indicate the existence of a complex involvement of the auditory pathways in FSHD1. Based on our findings, we suggest to maintain strict exclusion criteria when recruiting patients for such studies to avoid a possible bias of patient's selection and considering not only those subjects who complain about hearing problems, but all FSHD1 subjects. This approach may reveal a possible subclinical hearing dysfunction still unrecognized by the patient. Further studies are needed to evaluate hearing outcomes in the light of the progression of the disease and to better understand possible correlations between auditory impairment, muscular balance and genetic features. As to the absence of acoustic stapedial reflexes reported by Gheller et al. in their patients’ group, which we did not observe in our cohort, we can hypothesize this inconsistency is probably related to the small samples of both studies. It would be interesting to assess this issue in larger patients’ populations. In conclusion, our study (1) is supported by the evidence obtained, with other methods, by Gheller et al., in highlighting the importance of an early and comprehensive evaluation of auditory function in FSHD1 patients.

AUDITORY DYSFUNCTION IN FACIOSCAPULOHUMERAL MUSCULAR DYSTROPHY TYPE 1: BEYOND THE INNER EAR INVOLVEMENT.

To the Editor: We read with interest the article titled “Dysfunction Is a Frequent Feature of Facioscapulohumeral Muscular Dystrophy Type 1 (FSHD1)” by Frezza et al. (1), recently published in Otology and Neurotology. The above-mentioned study highlights that cochlear dysfunction may be the cause of the hearing loss in patients affected by FSHD. This statement is sustained by means of the investigation of the auditory function with multiple audiometric tests and with otoacoustic emissions. We recently performed an audiological evaluation of a cohort of 13 patients also with FSHD1 and some additional considerations can be made. The inclusion criteria of our patients (58.38 ± 8.18 yr; range, 48–74; five women) was self-reported or clinically diagnosed hearing loss (demographic and audiological data of the group present in Table 1). All patients underwent otoscopic evaluation and tympanogram (both normal for the whole cohort), audiometric testing with pure tone audiometry, frequency discrimination measurements, and event related potential P300 latency analysis. TABLE 1 - Demographic, genetic, and audiological data of the cohort Right Audiometry Left Audiometry PT Sex Age Ecori Fragment FSHD Score Class Age Onset HL (yrs) 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz 8000 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz 8000 Hz Reflexes 1 F 68 28 kb 6 B1 66 35 30 10 10 15 55 55 50 55 55 75 70 Absent 2 M 61 38 kb + 31 kb 7 A3 25 20 15 10 25 55 45 20 20 10 15 55 45 Absent 3 F 56 36 kb + 31 kb 4 A2 NPE 15 15 15 10 20 20 15 20 20 10 10 10 Absent 4 M 50 28 kb 6 A 2 NPE 20 20 20 25 65 35 35 30 20 25 70 35 Absent 5 F 74 35 kb 6 A3 NPE 10 10 15 40 55 70 10 10 15 40 65 65 Absent 6 M 61 21 kb 9 A2 58 15 15 15 20 30 40 15 15 20 15 20 15 Absent only at high frequencies 7 F 56 33 kb 8 A2 NPE 25 30 25 45 35 30 20 20 25 45 40 30 Absent 8 F 65 27 kb 2 B2 60 15 15 20 20 40 30 25 20 20 10 20 30 Absent 9 M 60 33 kb 0 C2 56 20 25 20 25 30 45 15 15 10 15 25 25 Absent only at high frequencies 10 M 63 33 kb 3 A2 60 10 10 20 25 65 10 10 10 20 35 50 15 Absent 11 M 48 32 kb 4 A3 45 25 40 40 40 35 35 10 20 20 25 15 10 Absent 12 M 48 32 kb 7 D1 42 10 10 20 30 25 35 15 15 20 45 25 20 Present bilaterally 13 M 49 38 kb + 33 kb 5 A3 NPE 15 15 15 10 30 30 10 15 15 10 30 30 Absent The result at pure tone audiometry for each frequency is expressed in dB HL.FSHD indicates facioscapulohumeral muscular dystrophy; HL, hearing loss; NPE, no previous evaluation; PT, patient; yrs, years. In our cohort, 5/13 (38%) patients reported a self-perceived hearing deficit despite no previous audiological evaluations. Only one patient reported no pathologic results at pure tone audiometry suggest that hearing loss in FSHD1 is a recurrently reported symptom (see Table 1). Noteworthy, a single patient had normal results but was evaluated because he reported hearing problems, most probably subclinical at this point. The analysis of the average results for each frequency revealed a descending configuration for the hearing threshold, with reduced hearing performance for high frequencies (higher than 2 kHz). Even though the pure tone average might be normal, a mild/moderate loss in high frequencies can be perceived by patients, especially when dealing with speech perception. To further investigate the hearing performance of these patients’ frequency discrimination measurements were performed. A set of 10 triplets of tones with equal intensity were presented to patients, at a comfortable listening level. In each triplet, one of the three tones had a different frequency compared with the other two, and patients were asked to identify the different tone. The difference in frequency had three different levels of difficulty for each of the two-frequency ranges (1000 and 2000 Hz). These tests resulted in pathologic in all patients. The event related potential P300 latency analysis revealed that all patients presented results in line with the hearing threshold. Notably, the impedance audiometry and the test of acoustic stapedial reflexes revealed that only one patient (1/13, 8%) presented normal acoustic stapedial reflexes. Also, the patient with normal hearing threshold presented absence of the acoustic stapedial reflexes. This observation can be considered interesting while dealing with these patients. In general, while considering a progressive hearing loss, the absence of reflexes is explained by a damage of the cochlea or the neural circuit crucial for the maintenance of this function. In the case of FSHD1, a hereditary muscle disease, the clinician should also consider the inefficiency of the contraction of the stapedial muscle as a possible cause of reflexes. So, even in patients with slight hearing loss, the stapedial reflexes can be absent due to the reduced function of this structure of the middle ear. Consequently, the absence of reflexes should not be considered a sign confirming a cochlear or retrocochlear nature of hearing loss. Noteworthy, 2/13 (15%) patients (number 1 and 11) presented an asymmetric hearing loss. This result may be due to the concomitant occurrence of other pathologic processes or to an asymmetric development of an FSHD1-related hearing loss that should be investigated over time. All the above-mentioned considerations added to the observations made by Frezza et al. (1) lead to the conclusion that hearing loss should be considered a frequent feature of FSHD1, but a thorough evaluation is necessary to ascertain the degree and the impact of the deficit. Even if the recent studies have shown novel findings concerning FSHD1 (2), conclusive data about hearing loss are not available and only future research will help in better defining this issue.