Centronuclear Myopathy

Centronuclear Myopathy

Article
Brain & Nerve
Bone, Muscle, & Joint
+5
Contributed byMaulik P. Purohit MD MPHApr 16, 2018

What are the other Names for this Condition? (Also known as/Synonyms)

  • CNM (Centronuclear Myopathy)

What is Centronuclear Myopathy? (Definition/Background Information)

  • Centronuclear Myopathy (CNM) refers to a group of rare, inherited conditions that affect the muscles
  • There are three main forms of the condition that are differentiated by their pattern of inheritance:
    • X-Linked Myotubular Myopathy
    • Autosomal Dominant Centronuclear Myopathy
    • Autosomal Recessive Centronuclear Myopathy
  • The cause of the condition and the associated signs and symptoms vary by subtype
  • Treatment is based on the signs and symptoms present in each person and may include physical and/or occupational therapy and assistive devices to help with mobility, eating and/or breathing

(Source: Centronuclear Myopathy; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

Who gets Centronuclear Myopathy? (Age and Sex Distribution)

  • Centronuclear Myopathy is a rare congenital disorder. The presentation of symptoms may occur at birth
  • Both males and females may be affected
  • Worldwide, individuals of all racial and ethnic groups may be affected

What are the Risk Factors for Centronuclear Myopathy? (Predisposing Factors)

  • A positive family history may be an important risk factor, since Centronuclear Myopathy is an inherited condition

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Centronuclear Myopathy? (Etiology)

Centronuclear Myopathy is a genetic disorder that is inherited in any of the following manner:

  • Autosomal dominant form
  • Autosomal recessive form
  • X-linked form

Autosomal dominant: Autosomal dominant conditions are traits or disorders that are present when only one copy of the mutation is inherited on a non-sex chromosome. In these types of conditions, the individual has one normal copy and one mutant copy of the gene. The abnormal gene dominates, masking the effects of the correctly function gene. If an individual has an autosomal dominant condition, the chance of passing the abnormal gene on to their offspring is 50%. Children, who do not inherit the abnormal gene, will not develop the condition or pass it on to their offspring.

Autosomal recessive: Autosomal recessive conditions are traits or disorders that occur when two copies of an abnormal gene have been inherited on a non-sex chromosome. If both parents have an autosomal recessive condition, there is a 100% likelihood of passing on the mutated genes to their children. If, however, only one mutant copy of the gene is inherited, the individual will be a carrier of the condition, but will not be present with any symptoms. Children born to two carriers, have a 25% chance of being homozygous dominant (unaffected), a 50% chance of being heterozygous (carrier), and a 25% chance of being homozygous recessive (affected).

What are the Signs and Symptoms of Centronuclear Myopathy?

Very frequently present symptoms in 80-99% of the cases:

  • Centrally nucleated skeletal muscle fibers
  • EMG abnormality
  • Gait disturbance
  • Muscular hypotonia (weak muscle tone)
  • Progressive muscle weakness

Frequently present symptoms in 30-79% of the cases:

  • External ophthalmoplegia (weak eye muscles)
  • Heart block
  • Mask-like facies; expression-less face
  • Ptosis (drooping eyelids)
  • Respiratory failure
  • Scoliosis (abnormal curvature of the spine)
  • Seizures

(Source: Centronuclear Myopathy; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

How is Centronuclear Myopathy Diagnosed?

Centronuclear Myopathy is diagnosed on the basis of the following information:

  • Complete physical examination
  • Thorough medical history evaluation
  • Assessment of signs and symptoms
  • Laboratory tests
  • Imaging studies
  • Biopsy studies, if necessary

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the Possible Complications of Centronuclear Myopathy?

The complications of Centronuclear Myopathy may include:

  • Severe cardiac abnormalities
  • Severe breathing difficulties
  • Mobility and quality of life may be affected

Complications may occur with or without treatment, and in some cases, due to treatment also.

How is Centronuclear Myopathy Treated?

Treatment is based on the signs and symptoms present in each person and may include physical and/or occupational therapy and assistive devices to help with mobility, eating and/or breathing

(Source: Centronuclear Myopathy; Genetic and Rare Diseases Information Center (GARD) of National Center for Advancing Translational Sciences (NCATS), USA.)

How can Centronuclear Myopathy be Prevented?

Currently, Centronuclear Myopathy may not be preventable, since it is a genetic disorder.

  • Genetic testing of the expecting parents (and related family members) and prenatal diagnosis (molecular testing of the fetus during pregnancy) may help in understanding the risks better during pregnancy
  • If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
  • Active research is currently being performed to explore the possibilities for treatment and prevention of inherited and acquired genetic disorders

Regular medical screening at periodic intervals with tests and physical examinations are recommended.

What is the Prognosis of Centronuclear Myopathy? (Outcomes/Resolutions)

  • The prognosis of Centronuclear Myopathy is dependent upon the severity of the signs and symptoms and associated complications, if any
  • Individuals with mild conditions have better prognosis than those with severe symptoms and complications
  • Typically, the prognosis may be assessed on a case-by-case basis

Additional and Relevant Useful Information for Centronuclear Myopathy:

The following DoveMed website link is a useful resource for additional information:

http://www.dovemed.com/diseases-conditions/rare-disorders/

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Maulik P. Purohit MD MPH picture
Approved by

Maulik P. Purohit MD MPH

Assistant Medical Director, Medical Editorial Board, DoveMed Team

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