XLMTM presents with a spectrum of severe signs and symptoms

Key clinical hallmarks of XLMTM1-9

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Several complications of XLMTM may be secondary to the generalized hypotonia, including9-13:

  • Inability to manage salivary secretions
  • Feeding difficulties characterized by swallowing, suckling, and chewing difficulties resulting in gastrostomy tube placement in >80% of patients
  • Thin or easily fractured bones
  • Delayed speech development
  • Scoliosis in >70% of patients, which can worsen over time and further impair breathing, requiring surgery
  • Abnormal bone development
  • Hepatobiliary disorders in 6% of patients

Cognitive development in patients with XLMTM

Cognitive development is normal in the majority of cases, but can be delayed in some patients with X-linked myotubular myopathy (XLMTM), potentially due to prolonged perinatal hypoxic episodes.11,13 Speech abnormalities in some cases due to dysarthria, respiratory insufficiency, and tracheostomy may be a confounding factor in accurately assessing cognitive function.13 Like motor function, cognitive development may be regularly and consistently assessed in patients with XLMTM using standardized assessment tools to better understand their long-term cognitive abilities.9


1. Graham RJ, et al. Arch Dis Child. 2020;105(4):332-338. 2. Genetic and rare diseases information center. Accessed January 19, 2021. https://rarediseases.info.nih.gov/diseases/11925/x-linked-myotubular-myopathy 3. Dowling JJ, et al. In: Adam MP, et al., eds. GeneReviews®. Published February 25, 2002. Updated August 23, 2018. https://www.ncbi.nlm.nih.gov/books/NBK1432/ 4. National organization for rare disorders. Accessed January 19, 2021. https://rarediseases.org/rare-diseases/x-linked-myotubular-myopathy/ 5. North KN, et al. Neuromuscul Disord. 2014;24(2):97-116. 6. Smith BK, et al. Muscle Nerve. 2014;50(3):315-326. 7. Pierson CR, et al. J Neuropathol Exp Neurol. 2005;64(7):555-564 8. Dowling JJ, et al. In: Adam MP, et al, eds. GeneReviews®. 2002. 9. Beggs AH, et al. Muscle Nerve. 2018:57(4):550-560. 10. Wang CH, et al. J Child Neurol. 2012;27(3):363-382. 11. Amburgey K, et al. Neurology. 2017;89(13):1355-1364. 12. Annoussamy M, et al. Neurology. 2019;92(16):e1852-e1867. 13. McEntagart M, et.al. Neuromuscul Disord. 2002;12(10):939-946.


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