Estimation of the Quality-of-Life Impact of X-Linked Myotubular Myopathy.
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SUBMITTER: Lloyd A
PROVIDER: S-EPMC8673490 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:X-linked recessive myotubular myopathy (XLMTM) is a severe congenital muscle disorder caused by mutations in the MTM1 gene and characterized by severe hypotonia and generalized muscle weakness in affected males. It is generally a fatal disorder during the neonatal period and early infancy. The diagnosis is based on typical histopathological findings on muscle biopsy, combined with suggestive clinical features. We experienced a case of a newborn who required intubation and ventilator care because of profound hypotonia and respiratory difficulty. The preliminary diagnosis at the time of request for retrieval was hypoxic ischemic encephalopathy, but the infant was clinically reevaluated for generalized weakness and muscle atrophy. Muscle biopsies showed variability in fiber size and centrally located nuclei in nearly all the fibers. We detected an MTM1 gene mutation of c.1261-1C>A in the intron 10 region, and diagnosed the neonate with myotubular myopathy. The same mutation was detected in his mother.
| S-EPMC3611049 | biostudies-literature
Project description:ObjectiveTo define the natural history of X-linked myotubular myopathy (MTM).MethodsWe performed a cross-sectional study that included an online survey (n = 35) and a prospective, 1-year longitudinal investigation using a phone survey (n = 33).ResultsWe ascertained data from 50 male patients with MTM and performed longitudinal assessments on 33 affected individuals. Consistent with existing knowledge, we found that MTM is a disorder associated with extensive morbidities, including wheelchair (86.7% nonambulant) and ventilator (75% requiring >16 hours of support) dependence. However, unlike previous reports and despite the high burden of disease, mortality was lower than anticipated (approximate rate 10%/y). Seventy-six percent of patients with MTM enrolled (mean age 10 years 11 months) were alive at the end of the study. Nearly all deaths in the study were associated with respiratory failure. In addition, the disease course was more stable than expected, with few adverse events reported during the prospective survey. Few non-muscle-related morbidities were identified, although an unexpectedly high incidence of learning disability (43%) was noted. Conversely, MTM was associated with substantial burdens on patient and caregiver daily living, reflected by missed days of school and lost workdays.ConclusionsMTM is one of the most severe neuromuscular disorders, with affected individuals requiring extensive mechanical interventions for survival. However, among study participants, the disease course was more stable than predicted, with more individuals surviving infancy and early childhood. These data reflect the disease burden of MTM but offer hope in terms of future therapeutic intervention.
| S-EPMC5649758 | biostudies-literature
Project description:ObjectivesBecause X-linked myotubular myopathy (XLMTM) is a rare neuromuscular disease caused by mutations in the MTM1 gene with a large phenotypic heterogeneity, to ensure clinical trial readiness, it was mandatory to better quantify disease burden and determine best outcome measures.MethodsWe designed an international prospective and longitudinal natural history study in patients with XLMTM and assessed muscle strength and motor and respiratory functions over the first year of follow-up. The humoral immunity against adeno-associated virus serotype 8 was also monitored.ResultsForty-five male patients aged 3.5 months to 56.8 years were enrolled between May 2014 and May 2017. Thirteen patients had a mild phenotype (no ventilation support), 7 had an intermediate phenotype (ventilation support less than 12 hours a day), and 25 had a severe phenotype (ventilation support 12 or more hours a day). Most strength and motor function assessments could be performed even in very weak patients. Motor Function Measure 32 total score, grip and pinch strengths, and forced vital capacity, forced expiratory volume in the first second of exhalation, and peak cough flow measures discriminated the 3 groups of patients. Disease history revealed motor milestone loss in several patients. Longitudinal data on 37 patients showed that the Motor Function Measure 32 total score significantly decreased by 2%. Of the 38 patients evaluated, anti-adeno-associated virus type 8 neutralizing activity was detected in 26% with 2 patients having an inhibitory titer >1:10.ConclusionsOur data confirm that XLMTM is slowly progressive for male survivors regardless of their phenotype and provide outcome validation and natural history data that can support clinical development in this population.Clinicaltrialsgov identifierNCT02057705.
| S-EPMC6550499 | biostudies-literature
Project description:Centronuclear myopathy (CNM) is an inherited neuromuscular disorder characterised by clinical features of a congenital myopathy and centrally placed nuclei on muscle biopsy.The incidence of X-linked myotubular myopathy is estimated at 2/100000 male births but epidemiological data for other forms are not currently available.The clinical picture is highly variable. The X-linked form usually gives rise to a severe phenotype in males presenting at birth with marked weakness and hypotonia, external ophthalmoplegia and respiratory failure. Signs of antenatal onset comprise reduced foetal movements, polyhydramnios and thinning of the ribs on chest radiographs; birth asphyxia may be the present. Affected infants are often macrosomic, with length above the 90th centile and large head circumference. Testes are frequently undescended. Both autosomal-recessive (AR) and autosomal-dominant (AD) forms differ from the X-linked form regarding age at onset, severity, clinical characteristics and prognosis. In general, AD forms have a later onset and milder course than the X-linked form, and the AR form is intermediate in both respects.Mutations in the myotubularin (MTM1) gene on chromosome Xq28 have been identified in the majority of patients with the X-linked recessive form, whilst AD and AR forms have been associated with mutations in the dynamin 2 (DNM2) gene on chromosome 19p13.2 and the amphiphysin 2 (BIN1) gene on chromosome 2q14, respectively. Single cases with features of CNM have been associated with mutations in the skeletal muscle ryanodine receptor (RYR1) and the hJUMPY (MTMR14) genes.Diagnosis is based on typical histopathological findings on muscle biopsy in combination with suggestive clinical features; muscle magnetic resonance imaging may complement clinical assessment and inform genetic testing in cases with equivocal features. Genetic counselling should be offered to all patients and families in whom a diagnosis of CNM has been made.The main differential diagnoses include congenital myotonic dystrophy and other conditions with severe neonatal hypotonia.Management of CNM is mainly supportive, based on a multidisciplinary approach. Whereas the X-linked form due to MTM1 mutations is often fatal in infancy, dominant forms due to DNM2 mutations and some cases of the recessive BIN1-related form appear to be associated with an overall more favourable prognosis.
| S-EPMC2572588 | biostudies-literature
Project description:X-linked myotubular myopathy (XLMTM) is a fatal pediatric disease where affected boys display profound weakness of the skeletal muscles. Possible therapies are under development but robust outcome measures in animal models are required for effective translation to human patients. We established a naturally-occurring canine model, where XLMTM dogs display clinical symptoms similar to those observed in humans. The aim of this study was to determine potential endpoints for the assessment of future treatments in this model. Video-based gait analysis was selected, as it is a well-established method of assessing limb function in neuromuscular disease and measures have been correlated to the patient's quality of life. XLMTM dogs (N = 3) and their true littermate wild type controls (N = 3) were assessed at 4-5 time points, beginning at 10 weeks and continuing through 17 weeks. Motion capture and an instrumented carpet were used separately to evaluate spatiotemporal and kinematic changes over time. XLMTM dogs walk more slowly and with shorter stride lengths than wild type dogs, and these differences became greater over time. However, there was no clear difference in angular measures between affected and unaffected dogs. These data demonstrate that spatiotemporal parameters capture functional changes in gait in an XLMTM canine model and support their utility in future therapeutic trials.
| S-EPMC4253544 | biostudies-literature
Project description:X-linked myotubular myopathy (XLMTM) is a severe monogenetic disorder of the skeletal muscle. It is caused by loss-of-expression/function mutations in the myotubularin (MTM1) gene. Much of what is known about the disease, as well as the treatment strategies, has been uncovered through experimentation in pre-clinical models, particularly the Mtm1 gene knockout mouse line (Mtm1 KO). Despite this understanding, and the identification of potential therapies, much remains to be understood about XLMTM disease pathomechanisms, and about the normal functions of MTM1 in muscle development. To lay the groundwork for addressing these knowledge gaps, we performed a natural history study of Mtm1 KO mice. This included longitudinal comparative analyses of motor phenotype, transcriptome and proteome profiles, muscle structure and targeted molecular pathways. We identified age-associated changes in gene expression, mitochondrial function, myofiber size and key molecular markers, including DNM2. Importantly, some molecular and histopathologic changes preceded overt phenotypic changes, while others, such as triad structural alternations, occurred coincidentally with the presence of severe weakness. In total, this study provides a comprehensive longitudinal evaluation of the murine XLMTM disease process, and thus provides a critical framework for future investigations.
| S-EPMC9346535 | biostudies-literature
Project description:Mutations in the MTM1 gene encoding myotubularin cause X-linked myotubular myopathy (XLMTM), a well-defined subtype of human centronuclear myopathy. Seven male Labrador Retrievers, age 14-26 wk, were clinically evaluated for generalized weakness and muscle atrophy. Muscle biopsies showed variability in fiber size, centrally placed nuclei resembling fetal myotubes, and subsarcolemmal ringed and central dense areas highlighted with mitochondrial specific reactions. Ultrastructural studies confirmed the centrally located nuclei, abnormal perinuclear structure, and mitochondrial accumulations. Wild-type triads were infrequent, with most exhibiting an abnormal orientation of T tubules. MTM1 gene sequencing revealed a unique exon 7 variant in all seven affected males, causing a nonconservative missense change, p.N155K, which haplotype data suggest derives from a recent founder in the local population. Analysis of a worldwide panel of 237 unaffected Labrador Retrievers and 59 additional control dogs from 25 other breeds failed to identify this variant, supporting it as the pathogenic mutation. Myotubularin protein levels and localization were abnormal in muscles from affected dogs, and expression of GFP-MTM1 p.N155K in COS-1 cells showed that the mutant protein was sequestered in proteasomes, where it was presumably misfolded and prematurely degraded. These data demonstrate that XLMTM in Labrador Retrievers is a faithful genetic model of the human condition.
| S-EPMC2930454 | biostudies-literature
Project description:X-linked myotubular myopathy (XLMTM) is a life-threatening rare neuromuscular disease, which is caused by pathogenic variants in the MTM1 gene. It has a large phenotypic heterogeneity, ranging from patients, who are able to walk independently to immobile patients who are only able to bring hand to mouth and depend on a respirator 24 hours a day every day. This suggests that ventilator requirements may not illustrate the full clinical picture of patients with XLMTM. At present, there is no curative therapy available, despite first promising results from ongoing gene therapy studies.In this study, we evaluated in detail the data from 13 German XLMTM patients, which was collected over a period of up to 20 years in our university hospital. We compared it to the international prospective longitudinal natural history study (NHS) data from 45 patients (containing 11 German patients). To highlight the broad phenotypic spectrum of the disease, we additionally focused on the clinical presentation of three cases at a glance.Comparing our data with the above mentioned natural history study, it appears the patients of the present German cohort seem to be more often severely affected, with higher frequency of non-ambulatory patients and patients on ventilation (and for longer time) and a higher proportion of patients needing a percutaneous endoscopic gastrostomy. Another key finding is a potential gap in time between first clinical presentation and final diagnosis, showing a need for patients to be treated in a specialized center for neuromuscular diseases.
| S-EPMC7902950 | biostudies-literature
Project description:The purpose of this study was to report the findings of clinical and genetic evaluation of a 3-month old male Boykin spaniel (the proband) that presented with progressive weakness. The puppy underwent a physical and neurological examination, serum biochemistry and complete blood cell count, electrophysiological testing, muscle biopsy and whole genome sequencing. Clinical evaluation revealed generalized neuromuscular weakness with tetraparesis and difficulty holding the head up and a dropped jaw. There was diffuse spontaneous activity on electromyography, most severe in the cervical musculature. Nerve conduction studies were normal, the findings were interpreted as consistent with a myopathy. Skeletal muscle was grossly abnormal on biopsy and there were necklace fibers and abnormal triad structure localization on histopathology, consistent with myotubular myopathy. Whole genome sequencing revealed a premature stop codon in exon 13 of MTM1 (ChrX: 118,903,496 C > T, c.1467C>T, p.Arg512X). The puppy was humanely euthanized at 5 months of age. The puppy's dam was heterozygous for the variant, and 3 male puppies from a subsequent litter all of which died by 2 weeks of age were hemizygous for the variant. This naturally occurring mutation in Boykin spaniels causes a severe form of X-linked myotubular myopathy, comparable to the human counterpart.
| S-EPMC7532942 | biostudies-literature
Project description:ObjectiveTo analyze the modulation of the phenotype in manifesting carriers of recessive X-linked myotubular myopathy (XLMTM), searching for possible genetic modifiers.MethodsTwelve Brazilian families with XLMTM were molecularly and clinically evaluated. In 2 families, 4 of 6 and 2 of 5 manifesting female carriers were identified. These females were studied for X chromosome inactivation. In addition, whole-exome sequencing was performed, looking for possible modifier variants. We also determined the penetrance rate among carriers of the mutations responsible for the condition.ResultsMutations in the MTM1 gene were identified in all index patients from the 12 families, being 4 of them novel. In the heterozygotes, X chromosome inactivation was random in 3 of 4 informative manifesting carriers. The disease penetrance rate was estimated to be 30%, compatible with incomplete penetrance. Exome comparative analyses identified variants within a segment of 4.2 Mb on chromosome 19, containing the killer cell immunoglobulin-like receptor cluster of genes that were present in all nonmanifesting carriers and absent in all manifesting carriers. We hypothesized that these killer cell immunoglobulin-like receptor variants may modulate the phenotype, acting as a protective factor in the nonmanifesting carriers.ConclusionsAffected XLMTM female carriers have been described with a surprisingly high frequency for a recessive X-linked disease, raising the question about the pattern of inheritance or the role of modifier factors acting on the disease phenotype. We demonstrated the possible existence of genetic mechanisms and variants accountable for the clinical manifestation in these women, which can become future targets for therapies.
| S-EPMC7524580 | biostudies-literature