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GTR Home > Tests > Myotubular Myopathy, X-linked

Indication

This is a clinical test intended for Help: Diagnosis, Mutation Confirmation

Clinical summary

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Imported from GeneReviews

X-linked myotubular myopathy (X-MTM), also known as myotubular myopathy (MTM), is characterized by muscle weakness that ranges from severe to mild. Approximately 80% of affected males present with severe (classic) X-MTM characterized by polyhydramnios, decreased fetal movement, and neonatal weakness, hypotonia, and respiratory failure. Motor milestones are significantly delayed and most individuals fail to achieve independent ambulation. Weakness is profound and often involves facial and extraocular muscles. Respiratory failure is nearly uniform, with most individuals requiring 24-hour ventilatory assistance. It is estimated that at least 25% of boys with severe X-MTM die in the first year of life, and those who survive rarely live into adulthood. Males with mild or moderate X-MTM (~20%) achieve motor milestones more quickly than males with the severe form; many ambulate independently, and may live into adulthood. Most require gastrostomy tubes and/or ventilator support. In all subtypes of X-MTM, the muscle disease is not obviously progressive. Female carriers of X-MTM are generally asymptomatic, although manifesting heterozygotes are increasingly being identified. In affected females, symptoms range from severe, generalized weakness presenting in childhood, with infantile onset similar to affected male patients, to mild (often asymmetric) weakness manifesting in adulthood. Affected adult females may experience progressive respiratory decline and ultimately require ventilatory support.

Clinical features

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Imported from Human Phenotype Ontology (HPO)

  • Arachnodactyly
  • Caesarian section
  • Cryptorchidism
  • Dandy-Walker syndrome
  • Diaphragmatic eventration
  • Tube feeding
  • Polyhydramnios
  • Hydrocephalus
  • Dental malocclusion
  • Hypokinesia
  • Premature birth
  • External ophthalmoplegia
  • Dolichocephaly
  • Areflexia
  • Decreased fetal movement
  • High forehead
  • Neck muscle weakness
  • High palate
  • Flexion contracture
  • Facial palsy
  • Congenital hypertrophic pyloric stenosis
  • Generalized muscle weakness
  • Long face
  • Narrow face
  • Birth length greater than 97th percentile
  • Severe muscular hypotonia
  • Elevated circulating hepatic transaminase concentration
  • Motor delay
  • Macrocephaly
  • Neonatal hypotonia
  • Slender toe
  • Respiratory failure requiring assisted ventilation
  • Neonatal respiratory distress
  • Low 1-minute APGAR score
  • Low 5-minute APGAR score
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Inheritance pattern

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X-linked inheritance

Conditions tested

Target population

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Not provided

Clinical validity

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Not provided

Clinical utility

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Not provided

Suggested reading

  • Frase, 2016
    Dream On: The Pursuit to Cure Myotubular Myopathy Born out of a Mother's Vision

Practice guidelines

  • EuroGenetest, 2012
    Clinical utility gene card for: Centronuclear and myotubular myopathies.

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