Hereditary Myopathy Research Articles

G.P.35: Analysis of a large patient cohort with recessive truncating TTN mutations reveals novel clinical features and a diverse range of muscle pathologies

TTN encodes titin, the largest human protein. In striated muscle two titin molecules align “head to head” to span the full length of the sarcomere, providing a scaffold for sarcomere organisation, a sensing and signalling hub, and both passive and active modulation of muscle contraction. Dominant mutations in TTN are established causes of cardiomyopathy, tibial muscular dystrophy, and hereditary myopathy with early respiratory failure. More recently, several individuals with two truncating mutations have been described with increased internalised nuclei (CNM) with or without multi-minicores (MMC). Using next generation sequencing, we identified 14 individuals from 11 families with compound heterozygous or homozygous truncating TTN mutations. Presentation was in utero or during infancy in all cases. Weakness of truncal and respiratory muscles was often prominent, and early-onset scoliosis and respiratory failure were common complications. Three affected individuals had dilated cardiomyopathy (DCM) or left ventricular dysfunction, and one carrier parent developed DCM in later life. Two individuals had congenital aortic abnormalities (coarctation and stenosis). Many affected individuals had distinctive clinical features which are unusual for congenital myopathies, including congenital or early-onset hand and foot deformities, congenital scoliosis, spinal rigidity, cleft palate, distal hypermobility and short stature. The most common histological abnormality was a mixed CNM-MMC pattern. Novel histological patterns included typical congenital fibre-type disproportion (CFTD) and CNM-MMC with caps and nemaline rods. The presence of palatal clefts, facial dysmorphology, and cardiac malformations in several individuals with TTN mutations suggests that titin plays a role in foetal development. Mutations in TTN should be considered in any individual with predominant truncal and respiratory weakness, and CNM, MMC, CFTD, caps, rods, or any combination of these, on muscle biopsy.

G.P.8: Dramatic improvement after injection augmentation in oculopharyngodistal myopathy

Oculopharyngodistal myopathy (OPDM) is a rare, adult-onset, slowly progressive hereditary vacuolar myopathy in which the weakness and atrophy affect oculofacial, pharyngeal and distal skeletal muscles. The underlying genetic defect is yet unknown. Swallowing difficulties and hoarseness due to oropharyngeal involvement are two of the most prominent features of the condition affecting the quality of life and survival of the patients. Swallowing difficulty due to cord paresis and atrophy causes aspiration, compromises respiration and cause premature death. Vocal fold injection augmentation with different types of materials is a method used to treat vocal cord paralysis, paresis, atrophy and scars. It is a safe, repeatable, practical and effective procedure and can be performed in awake patients or under general anesthesia. Here, we report the dramatic outcome after vocal cord injection augmentation in a 43 years old female patient with OPDM, evidenced by improvement in ENT examination, videolaryngostroboscopic evaluation, Voice Handicap Index (Validated in Turkish), MDVP Analysis, M.D. Anderson Dysphagia Inventory, FEES (Fiberoptic Endoscopic Evaluation of Swallowing). We examined the patient, and performed all the tests during preoperative and postoperative 1st week, 1st month and 3rd month visits. No complications occurred during or after the procedure. The method was very successful in that aspirations stopped immediately after the injection, the voice became less hoarse and speech was more understandable. Augmentation was more effective for aspiration than for voice quality. Oculopharyngodistal myopathy is a non-curable genetic disease which threatens life due to respiratory insufficiency even in ambulatory patients. Application of vocal cord injection augmentation can be a promising symptomatic therapy option to decrease or stop aspiration in patients with OPDM. A larger study with more patients and longer follow-up is ongoing.

Reply: Hereditary myopathy with early respiratory failure is caused by mutations in the titin FN3 119 domain

Sir, In the recent letters by Hedberg et al. (2013) and Pfeffer et al. (2013), the important question of genetic variants determining the pathogenesis of human myopathy with early respiratory failure (HMERF) was discussed. We welcome the attention and scientific discussion about the molecular causes and downstream pathogenic alterations in patients affected by this debilitating disease. We recognize the increasing evidence that mutations in titin domain A150 are the major and often dominant cause of HMERF. However, the conclusions the authors draw are debatable for several reasons. Firstly, the availability of next-generation sequencing, which was not available 9 years ago, allows us now to confirm from our own analysis that all affected members of the originally reported families in (Lange et al. , 2005) with the R279W titin kinase (TK) variant (TK nomenclature of residues as in PDB 1TKI to allow comparison) carry a second titin variant in the A150/Fn3 119 domain, P30091L, as also shown in a subset of these patients by Hedberg et al. (2013). Moreover, by clarifying the segregation in the …

Hereditary myopathy with early respiratory failure is associated with misfolding of the titin fibronectin III 119 subdomain

Hereditary myopathy with early respiratory failure is a rare disease with muscle weakness and respiratory failure as early symptoms. Muscle pathology is characterized by the presence of multiple cytoplasmic bodies and other protein aggregates in muscle fibers. The disease is associated with mutations in the titin gene (TTN). All patients harbor mutations located in exon 343 in the TTN gene that codes for the fibronectin III domain 119 (FN3 119) in the 10th motif of the 11-element motif A-band super-repeat. We investigated how such disease-causing mutations affect the biochemical behavior of this titin domain. All five disease-causing amino acid changes analyzed by us (p.P30068R, p.C30071R, p.W30088R, p.W30088C and p.P30091L) resulted in impaired FN3 119 domain solubility. In contrast, amino acid changes associated with common SNPs (p.V30076I, p.R30107C and p.S30125F) did not have this effect. In silico analyses further support the notion that disease-causing mutations impair proper folding of the FN3 119 domain. The results suggest that hereditary myopathy with early respiratory failure is caused by defective protein folding.

Muscle Disease

On the basis of strong research evidence, Duchenne muscular dystrophy (DMD), the most common severe childhood form of muscular dystrophy, is an X-linked recessive disorder caused by out-of-frame mutations of the dystrophin gene. Thus, it is classified asa dystrophinopathy. The disease onset is before age 5 years. Patients with DMD present with progressive symmetrical limb-girdle muscle weakness and become wheelchair dependent after age 12 years. (2)(3). On the basis of some research evidence,cardiomyopathy and congestive heart failure are usually seen in the late teens in patients with DMD. Progressive scoliosis and respiratory in sufficiency often develop once wheelchair dependency occurs. Respiratory failure and cardiomyopathy are common causes of death, and few survive beyond the third decade of life. (2)(3)(4)(5)(6)(7). On the basis of some research evidence, prednisone at 0.75 mg/kg daily (maximum dose, 40 mg/d) or deflazacort at 0.9 mg/kg daily (maximum dose, 39 mg/d), a derivative of prednisolone (not available in the United States), as a single morning dose is recommended for DMD patients older than 5 years, which may prolong independent walking from a few months to 2 years. (2)(3)(16)(17). Based on some research evidence, treatment with angiotensin-converting enzyme inhibitors, b-blockers, and diuretics has been reported to be beneficial in DMD patients with cardiac abnormalities. (2)(3)(5)(18). Based on expert opinion, children with muscle weakness and increased serum creatine kinase levels may be associated with either genetic or acquired muscle disorders (Tables 1 and 3). (14)(15)

Risk factors for osteoporosis, falls and fractures in hereditary myopathies and sporadic inclusion body myositis — A cross sectional survey

BackgroundThe risk of osteoporosis is known in myopathies requiring long-term steroid treatment and Pompe disease, but not in other hereditary myopathies or sporadic inclusion body myositis (sIBM). MethodsRisk factors of osteoporosis, laboratory parameters of bone metabolism, frequency of falls and fractures, walking ability, and pain were surveyed using questionnaires in 89 patients with sIBM and genetically confirmed myopathies facioscapulohumeral muscular dystrophy (FSHD), myotonic dystrophy types 1 and 2 (DM1, DM2), limb girdle muscular dystrophies (LGMD2A, LGMD2B, LGMD2I), MATR3 myopathy, and oculopharyngeal muscular dystrophy (OPMD). Additionally laboratory parameters of bone metabolism were determined. ResultsThe mean age at examination per disease group ranged from 32 years in LGMD2A to 70 years in sIBM. Myopathies with a higher degree of walking impairment had a higher risk of falls (sIBM, LGMD2A, LGMD2B). At the time of examination 3.4% had a history of osteoporosis. The 25-OH D3 level was decreased in 20% of patients (and in 55% of patients with LGMDs), 57% of them were ambulatory. The 25-OH D3 level was significantly lower in patients with myopathies than in other neurological disorders (p<0.001). 2.7 falls per year per person occurred. Fractures were reported in 6.8% of patients within the last year. They involved frequently the tibia bone. The pain score didn't correlate with either the walking disability (WGMS) score or the 25-OH D3 level. ConclusionThe risk for osteoporosis and reduced 25-OH D3 level seems to be increased in wheelchair-bound patients with myopathy but also in patients with DM1 and autosomal-recessive myopathies.

Role of sarcomeric gene polymorphisms on left ventricular dysfunction in coronary artery disease patients

Background Coronary artery disease (CAD) is a major cardiac disease in humans. Many CAD patients develop left ventricle dysfunction (LVD), leading to congestive heart failure. Mutations in several genes including those encoding sarcomeric proteins such as MYBPC3, TNNT2, and TTN are common genetic cause of hereditary cardiac myopathies. An intronic 25-bp deletion in MYBPC3 at 3’ region is associated with dilated (DCM) and hypertrophic (HCM) cardiomyopathies in Southeast Asia. We sought to determine the role of MYBPC3 25bp, TNNT2 5bp and TNN 18bp ins/del polymorphisms on LVD in CAD patients.

Myotonia in DNM2-related centronuclear myopathy

Centronuclear myopathy (CNM) is a rare hereditary myopathy characterized by centrally located muscle fiber nuclei. Mutations in the dynamin 2 (DNM2) gene are estimated to account for about 50% of CNM cases. Electromyographic recordings in CNM may show myopathic motor unit potentials without spontaneous activity at rest. Myotonic discharges, a distinctive electrical activity caused by membrane hyperexcitability, are characteristic of certain neuromuscular disorders. Such activity has been reported in only one CNM case without a known genetic cause. We sequenced the DNM2 gene and the genes associated with myotonia (CLCN1, SCN4A, DMPK and ZNF9) in a sporadic adult patient with CNM and myotonic discharges. Sequencing the entire coding region and exon-intron boundaries revealed a heterozygous c.1106g-a substitution in exon 8, resulting in a R369Q change in the DNM2. Sequencing the CLCN1, SCN4A, DMPK and ZNF9 genes ruled out mutations in these genes. This is the first report of DNM2-related CNM presenting with myotonia. The diagnosis of CNM should be considered in patients with myotonic discharges of an unknown cause.

A new disease allele for the p.C30071R mutation in titin causing hereditary myopathy with early respiratory failure

Hereditary myopathy with early respiratory failure is an autosomal dominant myopathy caused by mutations in the 119th fibronectin-3 domain of titin. To date all reported patients with the most common mutation in this domain (p.C30071R) appear to share ancestral disease alleles. We undertook this study of two families with the p.C30071R mutation to determine whether they share the same haplotype as previously reported British families or whether the mutation arose as a de novo event. We sequenced the 119th fibronectin-3 domain in these two probands and flanking polymorphisms associated with the British haplotype in hereditary myopathy with early respiratory failure. A family of Indian descent had a haplotype that was not compatible with the British shared haplotype. Cloning of the 119th fibronectin-3 domain in this patient demonstrated polymorphisms rs191484894 and novel noncoding variant c.90225C>T on the same allele as the mutation, which is distinct from previously reported British families. This proves that the p.C30071R mutation itself (rather than the haplotype containing this mutation) causes hereditary myopathy with early respiratory failure and suggests its independent origin in different ethnic groups.

Altered Tnnt3 characterizes selective weakness of fast fibers in mice overexpressing FSHD region gene 1 (FRG1)

Facioscapulohumeral muscular dystrophy (FSHD), a common hereditary myopathy, is characterized by atrophy and weakness of selective muscle groups. FSHD is considered an autosomal dominant disease with incomplete penetrance and unpredictable variability of clinical expression within families. Mice overexpressing FRG1 (FSHD region gene 1), a candidate gene for this disease, develop a progressive myopathy with features of the human disorder. Here, we show that in FRG1-overexpressing mice, fast muscles, which are the most affected by the dystrophic process, display anomalous fast skeletal troponin T (fTnT) isoform, resulting from the aberrant splicing of the Tnnt3 mRNA that precedes the appearance of dystrophic signs. We determine that muscles of FRG1 mice develop less strength due to impaired contractile properties of fast-twitch fibers associated with an anomalous MyHC-actin ratio and a reduced sensitivity to Ca(2+). We demonstrate that the decrease of Ca(2+) sensitivity of fast-twitch fibers depends on the anomalous troponin complex and can be rescued by the substitution with the wild-type proteins. Finally, we find that the presence of aberrant splicing isoforms of TNNT3 characterizes dystrophic muscles in FSHD patients. Collectively, our results suggest that anomalous TNNT3 profile correlates with the muscle impairment in both humans and mice. On the basis of these results, we propose that aberrant fTnT represents a biological marker of muscle phenotype severity and disease progression.

Orthopaedic Disorders in Myotonic Dystrophy Type 1: descriptive clinical study of 21 patients

BackgroundMyotonic Dystrophy Type 1 (DM1) is the most common form of hereditary myopathy presenting in adults. This autosomal-dominant systemic disorder is caused by a CTG repeat, demonstrating various symptoms. A mild, classic and congenital form can be distinguished. Often the quality of life is reduced by orthopaedic problems, such as muscle weakness, contractures, foot or spinal deformities, which limit patients’ mobility.The aim of our study was to gather information about the orthopaedic impairments in patients with DM1 in order to improve the medical care of patients, affected by this rare disease.MethodsA retrospective clinical study was carried out including 21 patients (11 male and 10 female), all diagnosed with DM1 by genetic testing. All patients were seen during our special consultations for neuromuscular diseases, during which patients were interviewed and examined. We also reviewed surgery reports of our hospitalized patients.ResultsWe observed several orthopaedic impairments: spinal deformities (scoliosis, hyperkyphosis, rigid spine), contractures (of the upper extremities and the lower extremities), foot deformities (equinus deformity, club foot, pes cavus, pes planovalgus, pes cavovarus, claw toes) and fractures.Five patients were affected by pulmonary diseases (obstructive airway diseases, restrictive lung dysfunctions). Twelve patients were affected by cardiac disorders (congenital heart defects, valvular heart defects, conduction disturbances, pulmonary hypertension, cardiomyopathy).Our patients received conservative therapy (physiotherapy, logopaedic therapy, ergotherapy) and we prescribed orthopaedic technical devices (orthopaedic custom-made shoes, insoles, lower and upper leg orthoses, wheelchair, Rehab Buggy). We performed surgery for spinal and foot deformities: the scoliosis of one patient was stabilized and seven patients underwent surgery for correction of foot deformities.ConclusionsAn orthopaedic involvement in DM1 patients should not be underestimated. The most common orthopaedic impairments are contractures, foot deformities and spinal deformities. Contractures are typically located distally in the lower extremities, but can also occur in the hip or shoulder joints. Foot deformities could be treated with orthopaedic custom-made shoes, orthoses or insoles. Surgery is indicated for severe foot deformities or contractures.

Reply: Hereditary myopathy with early respiratory failure is caused by mutations in the titin FN3 119 domain

Sir, The letter from Hedberg et al. (2013) is of great interest because it addresses an important question relating to the genetic aetiology of hereditary myopathy with early respiratory failure (HMERF). The original report by Lange et al. (2005) indicated that HMERF was associated with a heterozygous g.296459C>T/p.R32450W mutation in the kinase domain of titin ( TTN ) (using Genebank AJ277892 and Uniprot Q8WZ42 as the reference sequences). Since then, no further cases of HMERF caused by kinase domain mutations in TTN have been reported. In contrast, only a year since the report of a mutation in the 119th fibronectin-3 (FN3) domain of TTN causing HMERF (Ohlsson et al. , 2012; Pfeffer et al. , 2012), numerous reports have confirmed an association between the g.274375T>C/p.C30071R FN3 domain mutation and this disease, and seven other mutations have been reported affecting the same domain of titin (Izumi et al. , 2013; Palmio et al. , 2013; Pfeffer et al. , 2013; Toro et al. , 2013). Furthermore, our recent study screening 127 patients with myofibrillar myopathy for mutations in TTN revealed seven families with mutations in the 119th FN3 domain, but none with kinase domain mutations (Pfeffer et al. , 2013). Ostensibly, the patients from Lange et al. ’s (2005) original report were from three separate families, although …

Hereditary myopathy with early respiratory failure is caused by mutations in the titin FN3 119 domain

Sir, Hereditary myopathy with early respiratory failure (HMERF) is a neuromuscular disease associated with aggregation of various proteins in muscle fibres and muscle degeneration (Fig. 1) and was described in detail in several families by Edstrom et al. (1990). Linkage analyses indicated that the disease locus was in the distal part of the long arm of chromosome 2 (Nicolao et al. , 1999). Titin was a candidate gene and a missense variant that segregated with the disease in …

Idebenone in treatment of patients with Huntington's chorea and hereditary myopathy

Introduction: The treatment of Huntington's chorea and hereditary myopathy is absent. We studied the efficacy of energotropic therapy.

P.15.7 A founder mutation in the titin gene is a common cause of myofibrillar myopathy with early respiratory failure

Titin gene (TTN) mutations have been described in 8 families with hereditary myopathy with early respiratory failure (HMERF) a rare condition with features resembling myofibrillar myopathy (MFM). In order to verify if TTN mutations could be a cause of MFM, especially in presence of early respiratory involvement, we carried out a clinical and genetic analysis of 127 undiagnosed patients with a clinical presentation compatible with MFM. Sanger sequencing for the TTN mutations previously described in patients with HMERF (p.C30071R and p.R32450W) was performed in all patients. We identified 5 families with the p.C30071R mutation (3.9% of study population) likely due to a British founder effect. Affected subjects showed phenotypic features similar to previously reported cases, and muscle pathology demonstrated diagnostic features of MFM. Two further families had novel variants in the 119th FN3 domain (p.P30091L and p.N30145K). Although still with uncertain pathogenicity, these new variants suggest that other TTN mutations in this domain may cause MFM. Our results indicate that mutations in TTN gene cause MFM and titinopathy is more common than previously thought. We suggest that HMERF due to mutations in the TTN gene be nosologically classified as MFM-titinopathy.

P.15.8 Hereditary myopathy with early respiratory failure (HMERF) – Rapid increase of identified titinopathy families worldwide

Hereditary myopathy with early respiratory failure (HMERF) was described in 7 families from Sweden in 1990. One titin mutation in the kinase domain of titin gene in two of these families was identified 2005, but the further understanding of the disease remained elusive despite a few reports on families with somewhat similar phenotypes. This has now changed completely: within one year 6 new papers have reported the molecular genetic resolution in 27 different families with a worldwide distribution and occurrence in different ethnic populations: Caucasian, Japanese and Native American. This explosion of detailed clarification of HMERF was possible due to identification of a pathognomonic pattern of muscle involvement on MRI and, above all, due to the use of exome sequencing to clarify the molecular genetic cause. All 27 families have mutations in one single exon 343 of titin gene encoding the fibronectin-like FN3 119 domain (formerly A150) of A-band titin. The most common mutation, also surprisingly identified in different populations, is a C30071R change showing sharing of alleles on a common haplotype in most of the families. One of the new mutations showed semi-recessive inheritance pattern with subclinical myopathy in the heterozygous parents. Typical clinical features were respiratory failure at mid-adulthood in an ambulant patient with very variable degree of muscle weakness. The pathognomonic muscle MRI pattern shows most severe fatty degenerative changes in semitendinosus, obturatorius, gracilis, tibialis posterior and anterior. Cytoplasmic bodies reactive for thin filament and Z-disc proteins combined with rimmed vacuoles constitute the muscle pathology hallmarks. This extraordinary evolution of understanding HMERF disease indicates that the disease is much more common than previously thought and that exon 343 of TTN is the primary target for molecular diagnosis.

O.4 Proteomic analysis confirms that HMERF associated with mutations in A-band titin is a new subtype of myofibrillar myopathies

Hereditary myopathy with early respiratory failure (HMERF) caused by A-band TTN mutations shows a clinical and histopathological overlap with myofibrillar myopathies (MFM) characterized by disintegration of myofibrils and protein aggregation in muscle fibers. We applied a proteomic approach to decipher the aggregate composition in HMERF and compared the proteomic profile with findings in MFM subtypes. Nine skeletal muscle samples from HMERF patients with three different mutations in A-band titin and histopathological findings consistent with MFM were analyzed. Protein aggregates and intraindividual control samples (from aggregate-free muscle fibers) were collected by laser microdissection and analysed by a label-free mass spectrometric approach for identification and relative quantification of proteins. Fifty-eight proteins showed a statistically significant accumulation in aggregates with a ratio > 1.8 compared to control samples. The over-represented proteins desmin, filamin C, Xirp2, N-RAP, alphaB-crystallin, nestin, myotilin, Xin and Hsp27 were highly abundant in aggregates. The same was found in different MFM subtypes. The detection of further Z-disc proteins, chaperones, proteins involved in protein degradation and sarcolemmal proteins was also typical of MFM. In addition, we identified an over-representation of proteins that are involved in signaling pathways (e.g. inhibitors of the Rho/ROCK signaling pathway and ankyrin repeat domain-containing proteins). Titin was slightly but significant under-represented in aggregates (ratio 0.83). In conclusion, the proteomic profile of aggregates in HMERF associated with mutations in A-band titin is typical of MFM and confirms that this type of titinopathy is a new MFM subtype. The finding that titin is under-represented in aggregates indicates that aggregate formation is mediated by secondary effects. The detected over-representation of proteins involved in signaling pathways may play a role in pathogenesis.

Massive gastrointestinal dilatation in a case of hereditary hollow visceral myopathy

Massive gastrointestinal dilatation in a case of hereditary hollow visceral myopathy

Pain in adult patients with Pompe disease: A cross-sectional survey

BackgroundPompe disease is a rare hereditary metabolic myopathy caused by a deficiency of acid-α-glucosidase. We investigated the presence and severity of pain and its interference with daily activities in a large group of adults with Pompe disease, who we compared with an age-matched control group. MethodsData were collected in a cross-sectional survey in Germany and The Netherlands. Pain was assessed using the short-form brief pain inventory (BPI). Patients also completed the Short Form-36 item (SF-36v2), the Hospital Anxiety and Depression Scale (HADS) and the Rotterdam Handicap Scale (RHS). ResultsForty-five percent of the 124 adult Pompe patients reported having had pain in the previous 24h, against 27% of the 111 controls (p=0.004). The median pain severity score in Pompe patients reporting pain was 3.1 (on a scale from 0 to 10), indicating mild pain; against 2.6 amongst controls (p=0.06). The median score of pain interference with daily activities in patients who reported pain was 3.3, against 1.3 in controls (p=0.001). Relative to patients without pain, those with pain had lower RHS scores (p=0.02), lower SF-36 Physical and Mental component summary scores (p<0.001 and p=0.049), and higher levels of depression and anxiety (p=0.005 and p=0.003). ConclusionsTo date, this is one of the largest studies on pain in a specific neuromuscular disorder. Nearly one in two Pompe patients had experienced pain in the previous 24h. Although pain severity and its interference with daily life were mild, pain was related to a reduced quality of life, less participation in daily life, and greater depression and anxiety. Its management should therefore be seen as part of clinical practice involving Pompe patients.

Hereditary myopathy with early respiratory failure: occurrence in various populations

ObjectiveSeveral families with characteristic features of hereditary myopathy with early respiratory failure (HMERF) have remained without genetic cause. This international study was initiated to clarify epidemiology and the genetic underlying...