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Myotubular Myopathy 1 (XLMTM)


Relevance Rating: There is some evidence or research available for these breeds


Disease Name
Myotubular Myopathy 1 (XLMTM)
Mutation 2
c.1151A > C
Test Type
Genetic Disease/Disorder
Myotubular Myopathy is considered to be a rare sex-linked condition similar to centronuclear myopathy (CNM). It is characterized by progressive skeletal muscle atrophy causing short strides and slow movement compared to littermates and eventually fatally impairing the dog?s gait. Other signs include difficulty rising and walking, problems swallowing, and a hoarse bark. Age of onset from birth. Most dogs die or are euthanised by 4 months. This is of X-linked recessive inheritance, meaning male dogs born from a carrier female require just one copy of the mutation. The disease appears primarily in male dogs due to the sex-linked mode of inheritance.
Details 2
Mutations in the MTM1 gene encoding myotubularin cause X-linked myotubular myopathy (XLMTM), a well-defined subtype of human centronuclear myopathy... 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... (Beggs et al, 2010) Loss-of-function mutations in the myotubularin (MTM1) gene cause X-linked myotubular myopathy (XLMTM), a fatal, inherited pediatric disease that affects the entire skeletal musculature...The resulting canine phenotype resembles that of human patients with comparably severe mutations, and survival does not normally exceed 4 months... MTM1-mutant puppies display centrally-nucleated myofibers of reduced size and disrupted sarcotubular architecture progressing until the end of life, an average of 17 weeks. In-life measures of fore- and hind limb strength establish the rate at which XLMTM muscles weaken, and their corresponding decrease in gait velocity and stride length. Pulmonary function tests in affected dogs reveal a right-shifted relationship between peak inspiratory flow (PIF) and inspiratory time (TI); neurological assessments indicate that affected puppies as young as 10 weeks show early signs of neurological impairment... (From Goddard et al, 2015)
Beggs, A.H., Böhm, J., Snead, E., Kozlowski, M., Maurer, M., Minor, K., Childers, M.K., Taylor, S.M., Hitte, C., Mickelson, J.R., Guo, L.T., Mizisin, A.P., Buj-Bello, A., Tiret, L., Laporte, J., Shelton, G.D. : MTM1 mutation associated with X-linked myotubular myopathy in Labrador Retrievers. Proc Natl Acad Sci U S A 107:14697-702, 2010. Pubmed reference: 20682747. DOI: 10.1073/pnas.1003677107.
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