Muscular dystrophy

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Muscular dystrophy
assisted ventilation[1][2]
PrognosisDepends on the particular disorder[1]

Muscular dystrophies (MD) are a genetically and clinically heterogeneous group of rare

organs.[2]

Over 30 different disorders are classified as muscular dystrophies.[1][2] Of those, Duchenne muscular dystrophy (DMD) accounts for approximately 50% of cases and affects males beginning around the age of four.[1] Other relatively common muscular dystrophies include Becker muscular dystrophy, facioscapulohumeral muscular dystrophy, and myotonic dystrophy,[1] whereas limb–girdle muscular dystrophy and congenital muscular dystrophy are themselves groups of several – usually extremely rare – genetic disorders.

Muscular dystrophies are caused by

blood tests and genetic testing.[2]

There is no cure for any disorder from the muscular dystrophy group.

breathing muscles.[2]

Outcomes depend on the specific type of disorder.[1] Many affected people will eventually become unable to walk[2] and Duchenne muscular dystrophy in particular is associated with shortened life expectancy.

Muscular dystrophy was first described in the 1830s by Charles Bell.[2] The word "dystrophy" comes from the Greek dys, meaning "no, un-" and troph- meaning "nourish".[2]

Signs and symptoms

contractures
indicative of muscular dystrophy

The signs and symptoms consistent with muscular dystrophy are:[5]

  • Progressive muscular wasting
  • Poor balance
  • Scoliosis (curvature of the spine and the back)
  • Progressive inability to walk
  • Waddling gait
  • Calf deformation
  • Limited range of movement
  • Respiratory
    difficulty
  • Cardiomyopathy
  • Muscle spasms
  • Gowers' sign

Causes

The majority of muscular dystrophies are

de novo (spontaneous) mutation.[6][7]

Diagnosis

The diagnosis of muscular dystrophy is based on the results of

creatine phosphokinase (CpK3), electromyography, and genetic testing. A physical examination and the patient's medical history will help the doctor determine the type of muscular dystrophy. Specific muscle groups are affected by different types of muscular dystrophy.[8]

An MRI can be used to assess the white matter of the nervous system and measure the merosin levels in young boys. An absence of merosin in young boys will result with neurological deficits and changes in the white matter.[9]

Classification

Disorder name
OMIM
 Gene Inheritance pattern Age of onset Muscles affected Description
Becker muscular dystrophy 300376 DMD XR Childhood Distal limbs progressing to generalised weakness A less severe variant of Duchenne muscular dystrophy,[10] affects predominantly boys.
Congenital muscular dystrophy Multiple Multiple
AR
 At birth Generalised weakness Symptoms include general muscle weakness and possible joint deformities. Disease progresses slowly, and lifespan is shortened.

Congenital muscular dystrophy includes several disorders with a range of symptoms. Muscle degeneration may be mild or severe. Problems may be restricted to skeletal muscle, or muscle degeneration may be paired with effects on the brain and other organ systems.[11]

Several forms of the congenital muscular dystrophies are caused by defects in proteins thought to have some relationship to the dystrophin-glycoprotein complex and to the connections between muscle cells and their surrounding cellular structure. Some forms of congenital muscular dystrophy show severe brain malformations, such as lissencephaly and hydrocephalus.[10]

Duchenne muscular dystrophy 310200 DMD XR Childhood Distal limbs progressing to generalised weakness, involving respiratory muscles The most common childhood form of muscular dystrophy, affects predominantly boys (mild symptoms may occur in female carriers). Characterised by progressive muscle wasting. Clinical symptoms become evident when the child begins walking. By age 10, the child may need braces and by age 12, most patients are unable to walk.[12] Typical lifespans range from 15 to 45.[12] Sporadic mutations in this gene occur frequently.[13]
Distal muscular dystrophy
 		254130 DYSF
AR
 20–60 years Distal muscles in hands, forearms and lower legs Progress is slow and not life-threatening.[14]

Miyoshi myopathy, one of the distal muscular dystrophies, causes initial weakness in the calf muscles, and is caused by defects in the same gene responsible for one form of limb–girdle muscular dystrophy.[10]

Emery–Dreifuss muscular dystrophy Multiple Multiple
AR
 Childhood, early teenage years Distal limb muscles, limb-girdle, heart Symptoms include muscle weakness and wasting, starting in the distal limb muscles and progressing to involve the limb–girdle muscles. Most patients also have cardiac conduction defects and arrhythmias.[15][16]
Facioscapulohumeral muscular dystrophy 158900 DUX4
AD
 Adolescence Face, shoulders, upper arms, progressing to other muscles Causes progressive weakness, initially in the muscles of the face, shoulders, and upper arms. Additional muscles are often affected.[17] Affected individuals can become severely disabled, with 20% requiring a wheelchair by age 50.[18] 30% of cases involve spontaneous mutations.[18] Penetrance and severity seem to be lower in females compared to males.[18][19]
Limb–girdle muscular dystrophy Multiple Multiple
AR
 Any Upper arms and legs The person normally leads a normal life with some assistance. Rare cardiopulmonary complications can be life-threatening.[20]
Myotonic muscular dystrophy
 		160900
602668 		DMPK
CNBP
AD
 Adulthood Skeletal muscles, heart, other muscle groups Presents with myotonia (delayed relaxation of muscles), as well as muscle wasting and weakness.[21] Varies in severity and manifestations and affects many body systems in addition to skeletal muscles, including the heart, endocrine organs, and eyes.[22]
Oculopharyngeal muscular dystrophy 164300 PABPN1
AR
 40–50 years Eye muscles, face, throat, pelvis, shoulders

Management

Ankle foot orthosis

Currently, there is no cure for muscular dystrophy. In terms of management,

pacemaker.[26] The myotonia (delayed relaxation of a muscle after a strong contraction) occurring in myotonic muscular dystrophy may be treated with medications such as quinine.[27]

Low-intensity, assisted exercises, dynamic exercise training, or assisted bicycle training of the arms and legs during a 24-week trial significantly delayed the functional loss of muscular dystrophy. It can be done in a safe and feasible manner, even with boys late in their ambulation stage. However, eccentric exercises, or intense exercises causing soreness should not be used as they can cause further damage.[28]

Occupational therapy assists the individual with MD to engage in activities of daily living (such as self-feeding and self-care activities) and leisure activities at the most independent level possible. This may be achieved with use of adaptive equipment or the use of energy-conservation techniques. Occupational therapy may implement changes to a person's environment, both at home or work, to increase the individual's function and accessibility; furthermore, it addresses psychosocial changes and cognitive decline which may accompany MD, and provides support and education about the disease to the family and individual.[29]

Prognosis

Prognosis depends on the individual form of muscular dystrophy. Some dystrophies cause progressive weakness and loss of muscle function, which may result in severe physical disability and a life-threatening deterioration of respiratory muscles or heart. Other dystrophies do not affect life expectancy and only cause relatively mild impairment.[2]

History

In the 1860s, descriptions of boys who grew progressively weaker, lost the ability to walk, and died at an early age became more prominent in medical journals. In the following decade,

Guillaume Duchenne gave a comprehensive account of the most common and severe form of the disease, which now carries his name – Duchenne MD.[31]

Society and culture

In 1966 in the US and Canada, Jerry Lewis and the Muscular Dystrophy Association (MDA) began the annual Labor Day telecast The Jerry Lewis Telethon, significant in raising awareness of muscular dystrophy in North America. Disability rights advocates, however, have criticized the telethon for portraying those living with the disease as deserving pity rather than respect.[32]

On December 18, 2001, the

Muscular Dystrophy Coordinating Committee to help focus research efforts through a coherent research strategy.[33][34]

See also

References

  1. ^ a b c d e f g h i j k l m n "NINDS Muscular Dystrophy Information Page". NINDS. March 4, 2016. Archived from the original on 30 July 2016. Retrieved 12 September 2016.
  2. ^ a b c d e f g h i j k l m n o p q r "Muscular Dystrophy: Hope Through Research". NINDS. March 4, 2016. Archived from the original on 30 September 2016. Retrieved 12 September 2016.
  3. PMID 26140716
    .
  4. PMID 26140716
    .
  5. ^ Muscular Dystrophy Clinical Presentation at eMedicine
  6. ^ Choices, NHS. "Muscular dystrophy - Causes - NHS Choices". www.nhs.uk. Archived from the original on 2016-04-02. Retrieved 2016-04-10.
  7. ^ Griffiths, Anthony JF; Miller, Jeffrey H.; Suzuki, David T.; Lewontin, Richard C.; Gelbart, William M. (2000). Spontaneous mutations.[page needed]
  8. ^ "NIH /How is muscular dystrophy diagnosed?". NIH.gov. NIH. 2015. Archived from the original on 7 April 2016. Retrieved 10 April 2016.
  9. S2CID 31578361
    .
  10. ^
    MD CARE Act, as submitted by Department of Health and Human Service's National Institutes of Health
  11. ^ Congenital Muscular Dystrophy~clinical at eMedicine
  12. ^ a b "Duchenne muscular dystrophy: MedlinePlus Medical Encyclopedia". medlineplus.gov. Archived from the original on 2017-04-05. Retrieved 2017-03-14.
  13. ^ "Duchenne Muscular Dystrophy. What is muscular dystrophy? | Patient". Patient.info. 2016-04-15. Archived from the original on 2016-12-02. Retrieved 2017-03-14.
  14. PMID 21496636
    .
  15. ^ "OMIM Entry - # 310300 - EMERY-DREIFUSS MUSCULAR DYSTROPHY 1, X-LINKED; EDMD1". Omim.org. Archived from the original on 2017-03-10. Retrieved 2017-03-14.
  16. ^ "Emery-Dreifuss muscular dystrophy - Genetics Home Reference". Ghr.nlm.nih.gov. 2017-03-07. Archived from the original on 2017-03-12. Retrieved 2017-03-14.
  17. ^ "facioscapulohumeral muscular dystrophy - Genetics Home Reference". Ghr.nlm.nih.gov. Archived from the original on 2017-03-24. Retrieved 2017-03-14.
  18. ^
    PMID 27922500
    .
  19. ^ "Facioscapulohumeral muscular dystrophy: MedlinePlus Medical Encyclopedia". Nlm.nih.gov. 2017-03-09. Archived from the original on 2016-07-04. Retrieved 2017-03-14.
  20. ISBN 978-0906522-37-0
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  21. S2CID 2453622
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  22. PMID 20301344. Archived from the original on 2017-01-18. Retrieved 2017-03-14. {{cite book}}: |website= ignored (help
    )
  23. ^ a b "What are the treatments for muscular dystrophy?". NIH.gov. NIH. 2015. Archived from the original on 7 April 2016. Retrieved 10 April 2016.
  24. ^ "Muscular Dystrophy-OrthoInfo - AAOS". orthoinfo.aaos.org. Archived from the original on 2016-04-12. Retrieved 2016-04-10.
  25. PMID 22655512
    .
  26. PMID 21245364
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  27. ISBN 978-1-118-51797-0.[page needed
    ]
  28. S2CID 9990910
    .
  29. ISBN 978-0-323-00765-8
    .
  30. PMID 21912442
    .
  31. ^ "Muscular Dystrophy: Hope Through Research". National Institute of Neurological Disorders and Stroke. 23 March 2020. Retrieved 7 April 2020.
  32. ^ Berman, Ari (2011-09-02). "The End of the Jerry Lewis Telethon—It's About Time". The Nation. Retrieved 2017-03-14.
  33. ^ H.R. 717--107th Congress (2001) Archived 2012-02-19 at the Wayback Machine: MD-CARE Act, GovTrack.us (database of federal legislation), (accessed Jul 29, 2007)
  34. NIH
    website

Further reading

External links

Scholia has a topic profile for Muscular dystrophy.
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