Oculopharyngeal muscular dystrophy in Hispanic New Mexicans

Combined sequence and copy number analysis improves diagnosis of limb girdle and other myopathies

OBJECTIVE

Clinical and genetic heterogeneities make diagnosis of limb-girdle muscular dystrophy (LGMD) and other overlapping disorders of muscle weakness complicated and expensive. We aimed to develop a comprehensive next generation sequence-based multi-gene panel ("The Lantern Focused Neuromuscular Panel") to detect both sequence variants and copy number variants in one assay.

METHODS

Patients with clinical diagnosis of LGMD or other overlapping muscular dystrophies in the United States were tested by PerkinElmer Genomics in 2018-2021 via "The Lantern Project," a sponsored diagnostic testing program. Sixty-six genes related to LGMD subtypes- and other myopathies were investigated. Main outcomes were diagnostic yield, gene-variant spectrum, and LGMD subtypes' prevalence.

RESULTS

Molecular diagnosis was established in 19.6% (1266) of 6473 cases. Major genes contributing to LGMD were identified including CAPN3 (5.4%, 68), DYSF (4.0%, 51), GAA (3.7%, 47), ANO5 (3.6%, 45), and FKRP (2.7%, 34). Genes of other overlapping MD subtypes identified included PABPN1 (10.5%, 133), VCP (2.2%, 28), MYOT (1.2% 15), LDB3 (1.0%, 13), COL6A1 (1.5%, 19), FLNC (1.1%, 14), and DNAJB6 (0.8%, 10). Different sizes of copy number variants including single exon, multi-exon, and whole genes were identified in 7.5% (95) cases in genes including DMD, EMD, CAPN3, ANO5, SGCG, COL6A2, DOK7, and LAMA2.

INTERPRETATION

"The Lantern Focused Neuromuscular Panel" enables identification of LGMD subtypes and other myopathies with overlapping clinical features. Prevalence of some MD subtypes was higher than previously reported. Widespread deployment of this comprehensive NGS panel has the potential to ensure early, accurate diagnosis as well as re-define MD epidemiology.

Emerging and established biomarkers of oculopharyngeal muscular dystrophy

Oculopharyngeal muscular dystrophy (OPMD) is a rare, primarily autosomal dominant, late onset muscular dystrophy commonly presenting with ptosis, dysphagia, and subsequent weakness of proximal muscles. Although OPMD diagnosis can be confirmed with high confidence by genetic testing, the slow progression of OPMD poses a significant challenge to clinical monitoring and a barrier to assessing the efficacy of treatments during clinical trials. Accordingly, there is a pressing need for more sensitive measures of OPMD progression, particularly those which do not require a muscle biopsy. This review provides an overview of progress in OPMD biomarkers from clinical assessment, quantitative imaging, histological assessments, and genomics, as well as hypothesis-generating "omics" approaches. The ongoing search for biomarkers relevant to OPMD progression needs an integrative, longitudinal approach combining validated and experimental approaches which may include clinical, imaging, demographic, and biochemical assessment methods. A multi-omics approach to biochemical biomarker discovery could help provide context for differences found between individuals with varying levels of disease activity and provide insight into pathomechanisms and prognosis of OPMD.

Introducing the Dysphagiameter: a novel patient-reported outcome measure for evaluating dysphagia in oculopharyngeal muscular dystrophy - from conceptual framework to initial development

Oculopharyngeal muscular dystrophy (OPMD) is a rare late-onset muscle disease associated with progressive dysphagia. As there was no patient-reported outcome measure specific for the assessment of dysphagia in OPMD, the Dysphagiameter was developed. The Food and Drug Administration guidance was followed. In Phase 1, a systematic literature review and an expert consultation were conducted to identify the concepts of interest. It was decided that the instrument should assess difficulty swallowing using pictures of foods of various textures (part A) and impact of dysphagia on activities and participation (part B), as defined by the International Classification of Functioning, Disability and Health. In Phase 2, focus groups (n = 3) and online surveys (n = 55) were conducted to generate the items. Then, the food items for part A were selected and grouped into 17 textures by a panel of registered dietitians. Cognitive interviews were conducted (n = 23) to refine the instrument and assess its clarity and comprehensiveness. The final draft included 82 food items assessing the capacity to swallow foods and drinks (part A) and 10 items assessing the impact of dysphagia on activities and participation (part B). Item reduction and assessment of psychometrics properties, using Rasch analysis, are ongoing as part of Phase 3.

The phenotypic and genotypic features of Chinese patients with oculopharyngeal muscular dystrophy

OBJECTIVE

Oculopharyngeal muscular dystrophy (OPMD) is a late-onset inherited neuromuscular disorder, with progressive ptosis and dysphagia as common manifestations. To date, OPMD has rarely been reported among East Asians. The present study summarizes the phenotypic and genotypic features of Chinese patients with OPMD.

METHODS

Twenty-one patients with molecularly confirmed OPMD from 9 unrelated families were identified by direct sequencing of the polyadenlyate binding protein nuclear-1 (PABPN1) gene. Immunofluorescence staining of muscle biopsies was conducted to identify the components of protein degradation pathways involved in OPMD.

RESULTS

In our cohort, the genetically confirmed OPMD group had a mean age at onset of 50.6 ± 4.2 years (range 45-60 years). Ptosis (42.9%) was the most common initial symptom; patients with ptosis as the first symptom subsequently developed dysphagia within a median time of 5.5 years (range 1-19 years). Evidence of external ophthalmoplegia was found in 38.1% of patients. A total of 33.3% of the patients developed muscle weakness at a median age at onset of 66 years (range 50-70 years), with neck flexor involvement in all patients. Five genotypes were observed in our cohort, including classical (GCG)9-11 repeats in 7 families and non-GCG elongations with additional GCA expansions in 2 families. OPMD muscle biopsies revealed rimmed vacuoles and intranuclear filamentous inclusions. The PABPN1 protein showed substantial accumulation in the nuclei of muscle fiber aggregates and closely colocalized with p62, LC3B and FK2.

INTERPRETATION

Our findings indicate wide genetic heterogeneity in OPMD in the Chinese population and demonstrate abnormalities in protein degradation pathways in this disease.

Quantitative vs qualitative muscle MRI: Imaging biomarker in patients with Oculopharyngeal Muscular Dystrophy (OPMD)

Oculopharyngeal muscular dystrophy (OPMD) is a genetic muscle disease causing ptosis, severe swallowing difficulties and progressive limb weakness, although atypical presentations may be difficult to diagnose. Sensitive biomarkers of disease progression in OPMD are needed to enable more effective clinical trials. This study was designed to test the feasibility of using MRI to aid OPMD diagnosis and monitor OPMD progression. Twenty-five subjects with Dixon whole-body muscle MRI were enrolled: 10 patients with genetically confirmed OPMD, 10 patients with non-OPMD muscular dystrophies, and 5 controls. Using the MRI Dixon technique, muscle fat replacement was evaluated in the tongue, serratus anterior, lumbar paraspinal, adductor magnus, and soleus muscles using quantitative and semi-quantitative rating methods. Changes were compared with muscle strength testing, dysphagia severity, use of gait aids, and presence of dysarthria. Quantitative MRI scores of muscle fat replacement in the tongue could differentiate OPMD from other muscular dystrophies and from controls. Moreover, fat fraction in the tongue correlated with clinical severity of dysphagia. This study provides preliminary support for the use of Dixon-based quantitative MRI images as outcome measures for monitoring disease progression in clinical trials and provides rationale for future prospective studies aimed at methodological refinement and covariate identification.

Oculopharyngeal Muscular Dystrophy Ptosis, Mueller's Muscle Involvement, and a Review of Management Over 34 Years

PURPOSE

To review the management of the ptosis associated with oculopharyngeal muscular dystrophy (OPMD) from one author's experience over 34 years, demonstrate Mueller's muscle involvement in this disease, and how this impacts the preferred choice of surgery.

METHODS

Retrospective, nonrandomized comparative case series. Forty patients with OPMD who underwent primary bilateral ptosis surgery through an anterior eyelid incision and had their Mueller's muscle biopsied (one side) and sent for histopathologic analysis were selected for chart review. The main outcome measure was the presence or absence of dystrophic changes in the biopsied Mueller's muscle.

RESULTS

In 29/40 biopsies (72.5%), there were dystrophic changes and fatty infiltration of Mueller's muscle identified histopathologically.

CONCLUSIONS

Mueller's muscle is involved in the dystrophic process more often than expected contributing to ptosis in the OPMD syndrome. A combined Mueller's-aponeurotic advancement is more effective at elevating the eyelid than simply advancing the aponeurosis when Mueller's is fatty infiltrated at the time of external levator advancement surgery in our experience. Management strategies for ptosis surgery in OPMD are reviewed. The age of onset, levator muscle function, previous ptosis repair, how debilitated the patient is with their disease process systemically, as well as the presence of other eye problems (e.g., dry eye, prior glaucoma filtering procedures, history of corneal surgery, laser refractive procedure) are important clinical considerations in patients with OPMD.

Cross-cultural adaptation of the SWAL-QOL and the Sydney Swallow Questionnaire (SSQ) into French-Canadian and preliminary assessment for their use in an oculopharyngeal muscular dystrophy (OPMD) population

PURPOSE

Patient-reported outcomes (PRO) assessing dysphagia are an essential component of clinical trials to consider how patients feel and function in response to treatments. The selected PRO needs to be translated in several languages using a systematic process ensuring its validity and equivalence for use in multicenter clinical trials. The main objectives were to translate the SWAL-QOL and the Sydney Swallow Questionnaire (SSQ) into French Canadian (SWAL-QOL-FC and SSQ-FC) and to assess their appropriateness for patients with oculopharyngeal muscular dystrophy (OPMD).

METHODS

A forward- and back-translation process was followed including independent mother-tongue translators followed by committee review. Known-groups validity was assessed by comparing scores of OPMD French-Canadian participants (n = 21) known to differ in dysphagia severity according to the 80-ml drinking test score. A Mann-Whitney test was used to compare the mean scores. Cognitive interviews were conducted later on to ensure a posteriori cultural equivalence among French-Canadian participants (n = 28).

RESULTS

Evidences of adequate known-groups validity was shown for the SSQ-FC. Only two domains out of 10 of the SWAL-QOL-FC (burden and eating duration) showed adequate known-groups validity. In addition, the difference in the mean composite score was not significant. Several conceptual equivalence issues were found in both questionnaires as a result of the cognitive interviews.

CONCLUSION

This study provided evidence that the SSQ-FC presents better validity than the SWAL-QOL-FC in a small sample size of OPMD participants. The findings of the cognitive interviews suggest the need to develop an OPMD-specific questionnaire to capture better the whole spectrum of disease severity.

Guidelines for genetic testing of muscle and neuromuscular junction disorders

Despite recent advances in the understanding of inherited muscle and neuromuscular junction diseases, as well as the advent of a wide range of genetic tests, patients continue to face delays in diagnosis of sometimes treatable disorders. These guidelines outline an approach to genetic testing in such disorders. Initially, a patient's phenotype is evaluated to identify myopathies requiring directed testing, including myotonic dystrophies, facioscapulohumeral muscular dystrophy, oculopharyngeal muscular dystrophy, mitochondrial myopathies, dystrophinopathies, and oculopharyngodistal myopathy. Initial investigation in the remaining patients is generally a comprehensive gene panel by next-generation sequencing. Broad panels have a higher diagnostic yield and can be cost-effective. Due to extensive phenotypic overlap and treatment implications, genes responsible for congenital myasthenic syndromes should be included when evaluating myopathy patients. For patients whose initial genetic testing is negative or inconclusive, phenotypic re-evaluation is warranted, along with consideration of genes and variants not included initially, as well as their acquired mimickers.

Recent Progress in Oculopharyngeal Muscular Dystrophy

Oculopharyngeal muscular dystrophy (OPMD) is a late-onset intractable myopathy, characterized by slowly progressive ptosis, dysphagia, and proximal limb weakness. It is caused by the abnormal expansion of the alanine-encoding (GCN)n trinucleotide repeat in the exon 1 of the polyadenosine (poly[A]) binding protein nuclear 1 gene (11-18 repeats in OPMD instead of the normal 10 repeats). As the disease progresses, the patients gradually develop a feeling of suffocation, regurgitation of food, and aspiration pneumonia, although the initial symptoms and the progression patterns vary among the patients. Autologous myoblast transplantation may provide therapeutic benefits by reducing swallowing problems in these patients. Therefore, it is important to assemble information on such patients for the introduction of effective treatments in nonendemic areas. Herein, we present a concise review of recent progress in clinical and pathological studies of OPMD and introduce an idea for setting up a nation-wide OPMD disease registry in Japan. Since it is important to understand patients' unmet medical needs, realize therapeutically targetable symptoms, and identify indices of therapeutic efficacy, our attempt to establish a unique patient registry of OPMD will be a helpful tool to address these urgent issues.

Swallowing, Chewing and Speaking: Frequently Impaired in Oculopharyngeal Muscular Dystrophy

Background:

Oculopharyngeal muscular dystrophy (OPMD) is a late onset progressive neuromuscular disorder. Although dysphagia is a pivotal sign in OPMD it is still not completely understood.

Objective:

The aim of this study was to systematically investigate oropharyngeal functioning in a large OPMD population.

Methods:

Forty-eight genetically confirmed OPMD patients completed questionnaires, performed clinical tests on swallowing, chewing, speaking, tongue strength and bite force, and underwent videofluoroscopy of swallowing. Descriptive statistics was used for all outcomes and logistic regression to investigate predictors of abnormal swallowing.

Results:

Eighty-two percent reported difficulties with swallowing, 27% with chewing and 67% with speaking. Patients performed significantly worse on all oropharyngeal tests compared to age-matched controls except for bite force. Also asymptomatic carriers performed worse than controls: on chewing time, swallowing speed and articulation rate. During videofluoroscopy, all patients (except one asymptomatic) had abnormal residue and 19% aspirated. Independent predictors of abnormal residue were reduced swallowing capacity for thin liquids (OR 10 mL = 0.93; 20 mL = 0.95) and reduced tongue strength for thick liquids (OR 10 mL = 0.95); 20 mL = 0.90). Aspiration of thin liquids was predicted by disease duration (OR = 1.11) and post-swallow residue with 20 mL (OR = 4.03).

Conclusion:

Next to pharyngeal dysphagia, chewing and speaking are also frequently affected in OPMD patients, even in asymptomatic carriers. Residue after swallowing is a very early sign, while aspiration is a later sign in OPMD. For clinical follow-up monitoring of subjective complaints, swallowing capacity and tongue strength seems relevant.

Swallowing, Chewing and Speaking: Frequently Impaired in Oculopharyngeal Muscular Dystrophy

BACKGROUND

Oculopharyngeal muscular dystrophy (OPMD) is a late onset progressive neuromuscular disorder. Although dysphagia is a pivotal sign in OPMD it is still not completely understood.

OBJECTIVE

The aim of this study was to systematically investigate oropharyngeal functioning in a large OPMD population.

METHODS

Forty-eight genetically confirmed OPMD patients completed questionnaires, performed clinical tests on swallowing, chewing, speaking, tongue strength and bite force, and underwent videofluoroscopy of swallowing. Descriptive statistics was used for all outcomes and logistic regression to investigate predictors of abnormal swallowing.

RESULTS

Eighty-two percent reported difficulties with swallowing, 27% with chewing and 67% with speaking. Patients performed significantly worse on all oropharyngeal tests compared to age-matched controls except for bite force. Also asymptomatic carriers performed worse than controls: on chewing time, swallowing speed and articulation rate. During videofluoroscopy, all patients (except one asymptomatic) had abnormal residue and 19% aspirated. Independent predictors of abnormal residue were reduced swallowing capacity for thin liquids (OR 10 mL = 0.93; 20 mL = 0.95) and reduced tongue strength for thick liquids (OR 10 mL = 0.95); 20 mL = 0.90). Aspiration of thin liquids was predicted by disease duration (OR = 1.11) and post-swallow residue with 20 mL (OR = 4.03).

CONCLUSION

Next to pharyngeal dysphagia, chewing and speaking are also frequently affected in OPMD patients, even in asymptomatic carriers. Residue after swallowing is a very early sign, while aspiration is a later sign in OPMD. For clinical follow-up monitoring of subjective complaints, swallowing capacity and tongue strength seems relevant.

Oculopharyngeal Muscular Dystrophy, an Often Misdiagnosed Neuromuscular Disorder: A Southern California Experience

OBJECTIVE

Oculopharyngeal muscular dystrophy (OPMD) is a rare neuromuscular disorder characterized by late-onset development of bilateral eyelid ptosis, ophthalmoparesis and dysphagia with further progression to proximal limb muscle weakness that is an under recognized condition. The mode of inheritance is usually autosomal dominant, but a recessive form has been reported. OPMD is caused by a short expansion of the alanine repeat (GCN trinucleotide) in the poly(adenylate)-binding protein nuclear1 (PABPN1) gene.

METHODS

We performed a retrospective review of undiagnosed cases that initially presented with ptosis, diplopia, dysphagia, muscle weakness, muscular dystrophy and/or myasthenia gravis from 2000 to 2015 at two institutions in Southern California.

RESULTS

Twenty-five patients were identified to have OPMD with genetic confirmation.

CONCLUSIONS

Even though a rare condition, the prevalence is disproportionally frequent in certain ethnic groups and in certain regions; thus, we report our experience of OPMD patients in Southern California.

Established PABPN1 intranuclear inclusions in OPMD muscle can be efficiently reversed by AAV-mediated knockdown and replacement of mutant expanded PABPN1

Oculopharyngeal muscular dystrophy (OPMD) is a rare autosomal dominant late-onset muscular dystrophy affecting approximately 1:100 000 individuals in Europe. OPMD is mainly characterized by progressive eyelid drooping (ptosis) and dysphagia although muscles of the limbs can also be affected late in life. This muscle disease is due to a trinucleotide repeat expansion in the polyA-binding protein nuclear-1 gene. Patients express a protein with an 11-18 alanine tract that is misfolded and prone to form intranuclear inclusions, which are the hallmark of the disease. Other features of OPMD include muscle fibrosis and atrophy in affected muscles. Currently, no pharmacological treatments are available, and OPMD patients can only be referred to surgeons for cricopharyngeal myotomy or corrective surgery of extraocular muscles to ease ptosis. We recently tested a two-AAV `silence' and `replace' vector-based gene therapy treatment in a mouse model of OPMD. We demonstrate here that this gene therapy approach can revert already established insoluble aggregates and partially rescues the muscle from atrophy, which are both crucially important since in most cases OPMD patients already have an established disease when diagnosed. This strategy also prevents the formation of muscle fibrosis and stabilizes the muscle strength to the level of healthy muscles. Furthermore, we show here that similar results can be obtained using a single AAV vector incorporating both the `silence' and `replace' cassettes. These results further support the application of a gene therapy approach as a novel treatment for OPMD in humans.

The requirement for a disease-specific patient-reported outcome measure of dysphagia in oculopharyngeal muscular dystrophy

INTRODUCTION

There is no patient-reported outcome (PRO) questionnaire specifically designed to assess oropharyngeal dysphagia in oculopharyngeal muscular dystrophy (OPMD). To select a suitable questionnaire, content validity of the existing questionnaires must be assessed. This study sought (1) to identify dysphagia-related symptoms in OPMD and (2) to assess content validity of currently available PRO for the assessment of dysphagia severity in OPMD.

METHODS

A two-step literature review was conducted of dysphagia-related symptom identification and oropharyngeal dysphagia-related PRO. Symptoms were validated with an expert panel by using a Delphi survey. Content validity of PRO questionnaires was documented through content analysis.

RESULTS

Ten PRO questionnaires were identified. None of the questionnaires cover the entire symptom spectrum in OPMD and thus lack content validity.

DISCUSSION

The development and validation of a new PRO questionnaire to assess dysphagia in OPMD is required to establish the importance of symptomatic relief from new treatments. Muscle Nerve 59:445-450, 2019.

Diagnostics of short tandem repeat expansion variants using massively parallel sequencing and componential tools

Short tandem repeats (STRs) are scattered throughout the human genome. Some STRs, like trinucleotide repeat expansion (TRE) variants, cause hereditable disorders. Unambiguous molecular diagnostics of TRE disorders is hampered by current technical limitations imposed by traditional PCR and DNA sequencing methods. Here we report a novel pipeline for TRE variant diagnosis employing the massively parallel sequencing (MPS) combined with an opensource software package (FDSTools), which together are designed to distinguish true STR sequences from STR sequencing artifacts. We show that this approach can improve TRE diagnosis, such as Oculopharyngeal muscular dystrophy (OPMD). OPMD is caused by a trinucleotide expansion in the PABPN1 gene. A short GCN expansion, (GCN[10]), coding for a 10 alanine repeat is not pathogenic, but an alanine expansion is pathogenic. Applying this novel procedure in  a Dutch OPMD patient cohort, we found expansion variants from GCN[11] to GCN[16], with the GCN[16] as the most abundant variant. The repeat expansion length did not correlate with clinical features. However, symptom severity was found to correlate with age and with the initial affected muscles, suggesting that aging and muscle-specific factors can play a role in modulating OPMD.

Correlation between PABPN1 genotype and disease severity in oculopharyngeal muscular dystrophy

OBJECTIVE

Oculopharyngeal muscular dystrophy (OPMD) is an autosomal dominant adult-onset disease characterized by progressive ptosis, dysphagia, and proximal limb weakness. The genetic cause is an expanded (GCN)n mutation in the PABPN1 gene encoding for the polyadenylate-binding protein nuclear 1. We hypothesized a potential correlation between the size of the (GCN)n expansion and the severity of the phenotype. To do this, we characterized the distribution of the genotypes as well as their correlation with age at diagnosis and phenotypical features in a large cohort of heterozygous and homozygous patients with OPMD in France with a confirmed molecular diagnosis of PABPN1.

METHODS

We explored 354 unrelated index cases recruited between 1999 and 2014 in several neuromuscular centers in France.

RESULTS

This cohort allowed us to characterize the frequency of mutated alleles in the French population and to demonstrate a statistical correlation between the size of the expansion and the mean age at diagnosis. We also confirmed that homozygous patients present with a more severe disease.

CONCLUSIONS

It has been difficult to establish phenotype-genotype correlations because of the rare nature of this disease. Our work demonstrates that patients with OPMD with longer PABPN1 expansion are on average diagnosed at an earlier age than patients with a shorter expansion, confirming that polyalanine expansion size plays a role in OPMD, with an effect on disease severity and progression.

Clinical Outcomes of Frontalis Sling Using Silicone Rod With Two-point Brow Incisions in Blepharoptosis

PURPOSE

To investigate the functional and cosmetic outcomes of the modified frontalis sling operation using silicone rod with two-point brow incisions.

METHODS

A retrospective medical record review of 17 patients who underwent frontalis suspension surgery was performed. Functional outcomes were measured using habitual margin reflex distance. Cosmetic outcomes were investigated with contour analysis and a Patient Scar Assessment Questionnaire.

RESULTS

At the final visit, good and fair eyelid heights were achieved in 75% of patients in the unilateral group and 61.1% in the bilateral group. The average increase in margin reflex distance 1 was 1.9 mm in the unilateral group and 1.8 mm in the bilateral group. Satisfaction scores were 14.6, 8.2, and 11.8 for appearance, symptoms, and consciousness, respectively. In contour analysis, the normal arch generally increased.

CONCLUSIONS

Frontalis suspension with two-point brow incisions resulted in similar functional and cosmetic outcomes as the three-point brow incision technique. This study showed patient satisfaction with the aesthetic result after the frontalis sling procedure. [J Pediatr Ophthalmol Strabismus. 2016;53(4):224-232.].

The Dutch patients' perspective on oculopharyngeal muscular dystrophy: A questionnaire study on fatigue, pain and impairments

Research on oculopharyngeal muscular dystrophy focuses mainly on genetic and pathophysiological aspects. Clinically, oculopharyngeal muscular dystrophy is often considered as a disease with a relatively mild initial disease course with no or only mild functional disabilities. However the occurrence of fatigue, pain and functional impairments other than dysphagia has never been studied systematically. The aim of this study is therefore to assess the prevalence of fatigue, pain, and functional limitations, and the social participation and psychological well-being of oculopharyngeal muscular dystrophy patients. We performed a questionnaire study on fatigue, pain, functional impairments, social participation and psychological distress in 35 genetically confirmed oculopharyngeal muscular dystrophy patients with an average disease duration of 11.6 years. We showed that 19 (54%) of the patients experienced severe fatigue and also 19 (54%) experienced pain. Limitations in daily life activities and social participation were detected in 33 (94%) of the patients. Many patients reported pelvic girdle weakness and limitations in ambulation. Fatigue severity was related to functional impairments, while pain and disease duration were not. Psychological distress was not different from healthy adults. In conclusion, fatigue and pain are present among approximately half of the patients, and almost all patients are impaired in daily life activities, social participation and ambulation. These data should be taken into account in symptomatic management of oculopharyngeal muscular dystrophy.

Muscle weakness and speech in oculopharyngeal muscular dystrophy

PURPOSE

We documented speech and voice characteristics associated with oculopharyngeal muscular dystrophy (OPMD). Although it is a rare disease, OPMD offers the opportunity to study the impact of myopathic weakness on speech production in the absence of neurologic deficits in a relatively homogeneous group of speakers.

METHODS

Twelve individuals with OPMD and 12 healthy age-matched controls underwent comprehensive assessment of the speech mechanism including spirometry (respiratory support), nasometry (resonance balance), phonatory measures (pitch, loudness, and quality), articulatory measures (diadochokinetic rates, segment duration measures, spectral moments, and vowel space), tongue-to-palate strength measures during maximal isometric and speechlike tasks, quality-of-life questionnaire, and perceptual speech ratings by listeners.

RESULTS

Individuals with OPMD had substantially reduced tongue strength compared to the controls. However, little impact on speech and voice measures or on speech intelligibility was observed except for slower diadochokinetic rates.

CONCLUSIONS

Despite having less than half the maximal tongue strength of healthy controls, the individuals with OPMD exhibited minimal speech deficits. The threshold of weakness required for noticeable speech impairment may not have been reached by this group of adults with OPMD.

Hip flexion weakness is associated with impaired mobility in oculopharyngeal muscular dystrophy: a retrospective study with implications for trial design

Oculopharyngeal muscular dystrophy (OPMD) is a rare myopathy for which validated outcome measures are lacking, posing a barrier to clinical trials. Our goal was to identify factors associated with impaired mobility in OPMD in order to guide development of surrogate endpoints in future clinical trials. One hundred forty-four individuals with OPMD were included in this retrospective, single-center study. We made novel use of parametric time-to-event analysis to model age at initial use of assistive device for ambulation. We hypothesized that limb weakness and other markers of disease severity are associated with earlier use of assistive devices. 23.6% of individuals (34/144) progressed to use of assistive devices (mean age 66.0 ± 9.6 y). Earlier age at assistive device was associated with hip flexion Medical Research Council grade ≤3 (p <0.0001), earlier disease onset (p <0.0001), and lack of blepharoptosis surgery (p = 0.011). Markers of dysphagia severity were not associated with earlier progression to assistive devices. Our study is the first to show a statistical association between hip flexion weakness and impaired mobility in OPMD, indicating that hip flexion strength could be explored as a surrogate endpoint for use in clinical trials. Since severity of disease features may be discordant within individuals, composite outcome measures are warranted.

Ocular, bulbar, limb, and cardiopulmonary involvement in oculopharyngeal muscular dystrophy

OBJECTIVES

To assess skeletal muscle weakness and progression as well as the cardiopulmonary involvement in oculopharyngeal muscular dystrophy (OPMD).

MATERIALS AND METHODS

Cross-sectional study including symptomatic patients with genetically confirmed OPMD. Patients were assessed by medical history, ptosis, ophthalmoplegia, facial and limb strength, and swallowing capability. Cardiopulmonary function was evaluated using forced expiratory capacity in 1 s (FEV1), electrocardiogram (ECG), Holter monitoring, and echocardiography.

RESULTS

We included 13 symptomatic patients (six males, mean age; 64 years (41-80) from 8 families. Ptosis was the first symptom in 8/13 patients followed by limb weakness in the remaining 5 patients Dysphagia was never the presenting symptom. At the time of examination, all affected patients had ptosis or had previously been operated for ptosis, while ophthalmoplegia was found in 9 patients. Dysphagia, tested by cold-water swallowing test, was abnormal in 9 patients (17-116 s, ref <8 s). Six patients could not climb stairs of whom two were wheelchair bound and one used a rollator. Six patients had reduced FEV1 (range 23%-59%). No cardiac involvement was identified.

CONCLUSIONS

Limiting limb weakness is common in OPMD and can even be the presenting symptom of the disease. In contrast, dysphagia was not the initial symptom in any of our patients, although it was obligatory for diagnosing OPMD before genetic testing became available. Mild respiratory dysfunction, but no cardiac involvement, was detected.

Safety of botulinum toxin for dysphagia in oculopharyngeal muscular dystrophy

INTRODUCTION

Despite multiple studies reporting marked benefit of botulinum toxin (BTX) for treatment of cricopharyngeal dysphagia, little is known about its safety for this indication. We examined the safety of cricopharyngeal BTX for dysphagia in oculopharyngeal muscular dystrophy (OPMD).

METHODS

We reviewed records of patients with OPMD who received cricopharyngeal BTX.

RESULTS

Twenty-four patients underwent 66 procedures. Overall adverse event frequency was 44%. The most common adverse events were dysphonia (24%) and worsened dysphagia (14%). Logistic regression demonstrated that dose was a significant predictor of worsened dysphagia (P = 0.036) and of the composite event of dysphonia or worsened dysphagia (P = 0.009). There was a nonsignificant trend for dose as a predictor of dysphonia (P = 0.073). 59% of procedures were associated with symptomatic improvement.

CONCLUSIONS

While BTX appears to be beneficial for treatment of dysphagia in OPMD, caution is warranted when injecting the cricopharyngeus muscle due to dose-related risk of dysphonia or worsened dysphagia.

Oculopharyngeal muscular dystrophy as a cause of progression of weakness in antibody positive myasthenia gravis

Many neuromuscular conditions cause bulbar and limb weakness, and when several conditions coexist they present additional diagnostic challenges. Here we describe a case of a 45-year-old woman with antibody positive myasthenia gravis since age 16, who then develops treatment-resistant weakness due to genetically proven oculopharyngeal muscular dystrophy. We conclude that the development of treatment-resistant weakness in myasthenia gravis should spur further work up for other neuromuscular disorders including oculopharyngeal muscular dystrophy.

Polyadenylation-dependent control of long noncoding RNA expression by the poly(A)-binding protein nuclear 1

The poly(A)-binding protein nuclear 1 (PABPN1) is a ubiquitously expressed protein that is thought to function during mRNA poly(A) tail synthesis in the nucleus. Despite the predicted role of PABPN1 in mRNA polyadenylation, little is known about the impact of PABPN1 deficiency on human gene expression. Specifically, it remains unclear whether PABPN1 is required for general mRNA expression or for the regulation of specific transcripts. Using RNA sequencing (RNA–seq), we show here that the large majority of protein-coding genes express normal levels of mRNA in PABPN1–deficient cells, arguing that PABPN1 may not be required for the bulk of mRNA expression. Unexpectedly, and contrary to the view that PABPN1 functions exclusively at protein-coding genes, we identified a class of PABPN1–sensitive long noncoding RNAs (lncRNAs), the majority of which accumulated in conditions of PABPN1 deficiency. Using the spliced transcript produced from a snoRNA host gene as a model lncRNA, we show that PABPN1 promotes lncRNA turnover via a polyadenylation-dependent mechanism. PABPN1–sensitive lncRNAs are targeted by the exosome and the RNA helicase MTR4/SKIV2L2; yet, the polyadenylation activity of TRF4-2, a putative human TRAMP subunit, appears to be dispensable for PABPN1–dependent regulation. In addition to identifying a novel function for PABPN1 in lncRNA turnover, our results provide new insights into the post-transcriptional regulation of human lncRNAs.

In eukaryotic cells, protein-coding genes are transcribed to produce pre-messenger RNAs (pre–mRNAs) that are processed at the 3′ end by the addition of a sequence of poly-adenosine. This 3′ end poly(A) tail normally confers positive roles to the mRNA life cycle by stimulating nuclear export and translation. The fundamental role of mRNA polyadenylation is generally mediated by the activity of poly(A)-binding proteins (PABPs) that bind to the 3′ poly(A) tail of eukaryotic mRNAs. In the nucleus, the evolutionarily conserved poly(A)-binding protein PABPN1 is thought to be important for gene expression, as it stimulates mRNA polyadenylation in biochemical assays. Using a high-throughput sequencing approach that quantitatively measures the level of RNA expressed from all genes, we addressed the global impact of a PABPN1 deficiency on human gene expression. Notably, we found that most mRNAs were normally expressed in PABPN1–deficient cells, a result inconsistent with a role for PABPN1 in general mRNA metabolism. Surprisingly, our genome-wide analysis unveiled a new function for PABPN1 in a polyadenylation-dependent pathway of RNA decay that targets non-protein coding genes. Our discovery that PABPN1 functions in the regulation of noncoding RNAs raises the possibility that oculopharyngeal muscular dystrophy, a disease associated with mutations in the PABPN1 gene, is caused by defective expression of noncoding RNAs.

Magnetic resonance imaging and computed tomography of skeletal muscles in oculopharyngeal muscular dystrophy

OBJECTIVE

: To determine the spectrum of skeletal muscle involvement by neuroimaging in patients with oculopharyngeal muscular dystrophy (OPMD).

METHODS

: A neuroradiologist, blinded to severity of patients' dystrophy, retrospectively read 22 magnetic resonance or computed tomography images of the head, neck, chest, abdomen, pelvis, and proximal leg from 13 patients with OPMD. Imaged muscles were evaluated for degree of fatty infiltration and bulk in a semiquantitative fashion using similar images from age-matched patients lacking neuromuscular disease. Neurologic examinations were performed without knowledge of imaging results.

RESULTS

: We found abnormal tongue fatty infiltration in all patients and widespread infiltration in many other muscles. Over 50% of masseter, posterior neck, shoulder girdle, lumbar paraspinous, and gluteus muscles had abnormal fat.

CONCLUSION

: Although patients with OPMD have dysphagia with weak lids and proximal limbs, they have neuroimaging evidence of widespread fatty infiltration of many muscles. Excessive fatty infiltration of the tongue may help identify atypical patients with OPMD.

Mutation and haplotype analysis of oculopharyngeal muscular dystrophy in Thai patients

Oculopharyngeal muscular dystrophy (OPMD) is an inherited neuromuscular disease associated with a short trinucleotide repeat expansion in Exon 1 of the PABPN1 gene. OPMD is uncommon in East Asian populations, and there have been no previous reports of Thai patients. We studied clinical and molecular genetic features of six unrelated Thai patients with autosomal dominant OPMD. All patients had expansions of the guanine-cytosine-guanine (GCG) repeat ranging from three to seven additional repeats in the PABPN1 gene. Haplotype analysis showed that these mutations might have originated independently. Analysis of the size of the GCG repeat in the PABPN1 gene in 200 Thai control patients showed that 0.5% of the control subjects possessed (GCG)(7), thereby suggesting that the prevalence of autosomal recessive OPMD in the Thai population was approximately 1 in 160,000. In conclusion, our data suggest that OPMD in Thailand may be more common than previously thought.

The man who could not see what he could not eat

A 55-year-old Hispanic man born in New Mexico presented with progressively worsening bilateral upper eyelid ptosis and dysphagia. External levator advancement 5 years before did not improve his ptosis. A thorough systemic workup for myasthenia gravis was negative, but electromyography suggested a myopathic process. Molecular genetic testing was positive for oculopharyngeal muscular dystrophy.

Swallow characteristics in patients with oculopharyngeal muscular dystrophy

PURPOSE

This prospective investigation evaluates oral weakness and its impact on swallow function, weight, and quality of life in patients with oculopharyngeal muscular dystrophy (OPMD).

METHOD

Intraoral pressure, swallow pressure, and endurance were measured using an Iowa Oral Performance Instrument in participants with OPMD and matched controls. Timed water swallow, weight, and quality of life were also assessed.

RESULTS

Participants with OPMD were weaker than controls. Oral weakness impacted strength, swallow pressure, swallow capacity, swallow volume, swallow time, and quality of life. Tongue endurance was not affected by oral weakness.

CONCLUSION

This investigation provides further insight into the swallow function of patients with myopathic disease. Muscle fiber loss leads to weakness, which results in reductions in swallow function and quality of life. Weight and endurance are not greatly altered.

Oculopharyngeal muscular dystrophy: a polyalanine myopathy

It has been 10 years since the identification of the first PABPN1 gene (GCN)(n)/polyalanine mutations responsible for oculopharyngeal muscular dystrophy (OPMD). These mutations have been found in most cases of OPMD diagnosed in more than 35 countries. Sequence analyses have shown that such mutations have occurred numerous times in human history. Although PABPN1 was found early on to be a component of the classic filamentous intranuclear inclusions (INIs), mRNA and other proteins also have been found to coaggregate in the INIs. It is still unclear if the INIs play a pathologic or a protective role. The generation of numerous cell and animal models of OPMD has led to greater insight into its complex molecular pathophysiology and identified the first candidate therapeutic molecules. This paper reviews basic and clinical research on OPMD, with special emphasis on recent developments in the understanding of its pathophysiology.

Study of a Taiwanese family with oculopharyngeal muscular dystrophy

BACKGROUND

Oculopharyngeal muscular dystrophy (OPMD) is a late onset autosomal dominant muscle disorder. OPMD is caused by a short trinucleotide repeat expansion encoding an expanded polyalanine tract in the polyadenylate binding-protein nuclear 1 (PABPN1) gene. We identified and characterized a PABPN1 mutation in a Taiwanese family with OPMD.

METHODS

The phenotypic and genotypic characteristics of all subjects were evaluated in a Taiwanese OPMD family. Genetic alterations in the PABPN1 gene were identified using PCR and DNA sequencing.

RESULTS

Ten subjects with OPMD (6 symptomatic and 4 asymptomatic) within the Taiwanese family carried a novel mutation in the PABPN1 gene. The normal (GCG)6(GCA)3GCG sequence was replaced by (GCG)6(GCA)(GCG)4(GCA)3GCG due to an insertion of (GCG)4GCA into the normal allele in the Taiwanese OPMD subjects.

CONCLUSIONS

In contrast to a single GCG expansion in most of OPMD patients in the literature, an insertion of (GCG)4GCA in the PABPN1 gene was found in the Taiwanese OPMD subjects. The identification of this mutation appears to support the molecular mechanism of unequal cross-over of two PABPN1 alleles.

Postoperative complications in patients with oculopharyngeal muscular dystrophy: a retrospective study

PURPOSE

Oculopharyngeal muscular dystrophy (OPMD) is a genetic disease with autosomal dominant transmission particularly common in Quebec where its prevalence is about 1:1000. The main features are bilateral ptosis of the eyelids and dysphagia. These symptoms are frequently treated surgically by levator palpebrae resection (LPR) and cricopharyngeal myotomy (CPM). The objectives of this retrospective chart review were to describe the postoperative complications in OPMD patients undergoing LPR or CPM and to determine their incidence.

METHODS

Medical records of all OPMD patients who had either LPR or CPM between 1997 and 2002 were reviewed. The following complications were collected: death, pneumonia, aspiration pneumonitis, airway obstruction, reintubation, and severe coughing and choking caused by profuse secretions.

RESULTS

One hundred and fourteen surgeries on 92 OPMD patients were studied. Fifty-nine were LPR under general anesthesia (LPR-GA) and 22 were LPR under local anesthesia (LPR-LA). Thirty-three surgeries were CPM, all under general anesthesia. There was no death or reintubation. Patients who had LPR-LA had shorter postanesthesia care unit (P<0.001) and ambulatory surgery unit (P<0.001) stays than those who had LPR-GA. Complications were more frequent after CPM than LPR-GA (P<0.001).

CONCLUSION

The complication rate after LPR was low. Both local and general anesthesia are safe alternatives in OPMD patients operated for LPR. Patients having CPM presented more respiratory complications than those having LPR.

Identification of a novel mutation in a Korean patient with oculopharyngeal muscular dystrophy

Oculopharyngeal muscular dystrophy (OPMD) is a late-onset muscle disorder characterized by progressive dysphagia and bilateral ptosis. Mutations in the polyadenylate binding protein nuclear 1 (PABPN1) gene have been found to cause OPMD. The typical mutation is a stable trinucleotide repeat expansion in the first exon of the PABPN1 gene, in which (GCG)(6) is the normal repeat length. We investigated a Korean patient with OPMD and identified a novel mutation: a heterozygous insertion of a 9-bp sequence [(GCG)(GCA)(GCA); c.27_28insGCGGCAGCA] instead of the (GCG) repeat expansion, resulting in an in-frame insertion of three alanines (p.A10insAAA). To the best of our knowledge, this is the first report of a genetically confirmed case of OPMD in Korea.

[Cardiac manifestations of muscular dystrophies]

Muscular dystrophies (MD) are a clinically and genetically heterogeneous disease group. In the last few years, remarkable progress has been made in understanding the close und various relations between skeletal muscle disease and heart muscle disease. Cardiac involvement has been documented in a number of primary MDs and is even the dominant feature in some of them. The myocardium can be affected in the form of a dilated cardiomyopathy while the conduction system can be affected resulting in arrhythmias and conduction defects. Many patients with MD die because of cardiac complications like sudden cardiac death or congestive heart failure. Detailed clinical data about cardiac involvement are available for Duchenne/Becker MD, Emery-Dreifuss MD, myotonic dystrophy, and the different limb girdle MDs. Cardiac manifestations were also found in congenital MD, central core disease, proximal myotonic myopathy, and nemaline myopathy. No data about cardiac abnormalities are available in oculopharyngeal MD and rippling muscle disease. The heart of patients with primary MD should be carefully investigated because of the life-threatening events caused by cardiac complications. There is a strong need for a close collaboration between neurologists and cardiologists in order to provide optimal disease management for the affected patients.

Frontalis suspension for upper eyelid ptosis: evaluation of different surgical designs and suture material

PURPOSE

To compare two sling designs (single loop or double pentagon) and a variety of suture material that was used in frontalis suspension surgery for correction of upper eyelid ptosis.

DESIGN

Retrospective, nonrandomized, comparative interventional case series.

METHODS

Medical record review of 99 patients (164 surgeries) who underwent frontalis suspension surgery for upper eyelid ptosis was conducted at the Jules Stein Eye Institute in 1996 to 2002. Functional and cosmetic success, margin reflex distance (MRD) and lagophthalmos were evaluated.

RESULTS

MRD increased an average of 1.1 mm after the operation (P < .001). Ptosis recurrence was noticed in 42 cases (26%); polytetrafluoroethylene achieved the lowest recurrence rate (15%), although not statistically significant. No difference in functional success, ptosis recurrence, or change in MRD was noticed between single loop and double pentagon design. A better cosmetic outcome was noted in cases in which nylon suture was used. Complications included four cases (2.4%) of over-correction, three cases (1.8%) of suture infection (all in polytetrafluoroethylene), two cases of pyogenic granuloma (1.2%), and two cases (1.2%) of suture exposure.

CONCLUSION

Frontalis suspension for upper eyelid ptosis resulted in 26% ptosis recurrence after a mean of 12 months from first surgery. Polytetrafluoroethylene showed the lowest incidence of ptosis recurrence. No statistically significant difference was found between different suture materials or loop shape that was used in the surgical technique. A better cosmetic outcome, as graded by different observers, was noted in cases in which a nylon sling was used.

Oculopharyngeal muscular dystrophy with PABPN1 mutation in a Chinese Malaysian woman

Oculopharyngeal muscular dystrophy (OPMD) is an autosomal dominant disorder of middle age presenting as progressive dysphagia and eyelid ptosis, due to short expansions of the GCG trinucleotide repeat (from GCG6 to GCG8-13) in the polyadenylate binding-protein nuclear 1 (PABPN1) gene. OPMD is rarely seen in Asians and morphologically and/or genetically confirmed cases have been reported in Japanese kindreds only. We report a 64 year old Chinese-Malaysian woman who presented with progressive dysphagia and bilateral ptosis for about 6 years. Her mother and elder brother (both deceased) were believed to be affected. Muscle histopathology revealed angulated fibres with rimmed vacuoles. Genetic analysis showed repeat expansion in one allele to (GCG)9 while normal in the other (GCG)6. This is the first non-Japanese Asian family with genetically confirmed OPMD.

Obstructive sleep apnea syndrome complicating oculopharyngeal muscular dystrophy

We report a 75-year-old Spanish-American woman who received a diagnosis of oculopharyngeal muscular dystrophy after presenting with ptosis and dysphagia. She also complained of snoring and daytime somnolence, and was found to have obstructive sleep apnea (OSA) syndrome attributable to her neuromuscular disorder. This is the first report of OSA syndrome complicating typical, adult-onset oculopharyngeal muscular dystrophy, and should prompt the evaluation of other such patients for sleep-disordered breathing.

Oculopharyngeal muscular dystrophy: a late-onset polyalanine disease

Oculopharyngeal muscular dystrophy (OPMD) is a muscle disease of late onset associated with progressive ptosis of the eyelids, dysphagia, and unique tubulofilamentous intranuclear inclusions (INIs). OPMD is usually transmitted as an autosomal dominant trait (OMIM 164300). A rarer allelic autosomal recessive form has also been observed (OMIM 257950). Both forms are caused by short (GCG)8-13 expansions in the polyadenylate-binding protein nuclear 1 gene (PABPN1) located on chromosome 14q11.1. The mutations cause the lengthening of an N-terminal polyalanine domain. Both slippage and unequal recombination have been proposed as the mutation mechanisms. The size of the mutation has not yet been conclusively shown to inversely correlate with the severity of the phenotype. Mutated PABPN1 proteins have been shown to be constituents of the INIs. The INIs also contain ubiquitin, proteasome subunits, HSP 40, HSP 70, SKIP, and abundant poly(A)-mRNA. The exact mechanism responsible for polyalanine toxicity in OPMD is unknown. Various intranuclear inclusion dependent and independent mechanisms have been proposed based on the major known function of PABPN1 in polyadenylation of mRNA and its shuttling from the nucleus to the cytoplasm. OPMD is one of the few triplet-repeat diseases for which the function of the mutated gene is known. Because of the increasing number of diseases caused by polyalanine expansions and the pathological overlap with CAG/polyglutamine diseases, what pathological insight is gained by the study of OPMD could lead to a better understanding of a much larger group of developmental and degenerative diseases.