GetWiki

{{Short description|Genetic disorder}}

factoids

Muscular dystrophies (MD) are a genetically and clinically heterogeneous group of rare neuromuscular diseases that cause progressive weakness and breakdown of skeletal muscles over time. The disorders differ as to which muscles are primarily affected, the degree of weakness, how fast they worsen, and when symptoms begin. Some types are also associated with problems in other organs.WEB, March 4, 2016, Muscular Dystrophy: Hope Through Research,weblink dead,weblink" title="web.archive.org/web/20160930165657weblink">weblink 30 September 2016, 12 September 2016, NINDS, Over 30 different disorders are classified as muscular dystrophies. Of those, Duchenne muscular dystrophy (DMD) accounts for approximately 50% of cases and affects males beginning around the age of four. Other relatively common muscular dystrophies include Becker muscular dystrophy, facioscapulohumeral muscular dystrophy, and myotonic dystrophy, whereas limb–girdle muscular dystrophy and congenital muscular dystrophy are themselves groups of several – usually extremely rare – genetic disorders.Muscular dystrophies are caused by mutations in genes, usually those involved in making muscle proteins. The muscle protein, dystrophin, is in most muscle cells and works to strengthen the muscle fibers and protect them from injury as muscles contract and relax.BOOK, Comprehensive Physiology, 2011-01-17, Wiley, 978-0-470-65071-4, Terjung, Ronald, 1, en, 10.1002/cphy.c140048, 4767260, 26140716, Gao, Q. Q., McNally, E. M., 5, 3, 1223–1239, It links the muscle membrane to the thin muscular filaments within the cell. Dystrophin is an integral part of the muscular structure. An absence of dystrophin can cause impairments: healthy muscle tissue can be replaced by fibrous tissue and fat, causing an inability to generate force.JOURNAL, Gao, Quan Q., McNally, Elizabeth M., 2015-06-24, The Dystrophin Complex: Structure, Function, and Implications for Therapy,weblink Comprehensive Physiology, 5, 3, 1223–1239, 10.1002/cphy.c140048, 4767260, 26140716, 9780470650714, Respiratory and cardiac complications can occur as well. These mutations are either inherited from parents or may occur spontaneously during early development. Muscular dystrophies may be X-linked recessive, autosomal recessive, or autosomal dominant. Diagnosis often involves blood tests and genetic testing.There is no cure for any disorder from the muscular dystrophy group. Several drugs designed to address the root cause are currently available including gene therapy (Elevidys), and antisense drugs (Ataluren, Eteplirsen etc.). Other medications used include glucocorticoids (Deflazacort, Vamorolone); calcium channel blockers (Diltiazem); to slow skeletal and cardiac muscle degeneration, anticonvulsants to control seizures and some muscle activity, and Histone deacetylase inhibitors (Givinostat) to delay damage to dying muscle cells. Physical therapy, braces, and corrective surgery may help with some symptoms while assisted ventilation may be required in those with weakness of breathing muscles.Outcomes depend on the specific type of disorder.WEB, NINDS Muscular Dystrophy Information Page,weblink NINDS, 12 September 2016, March 4, 2016, dead,weblink" title="web.archive.org/web/20160730004520weblink">weblink 30 July 2016, Many affected people will eventually become unable to walk and Duchenne muscular dystrophy in particular is associated with shortened life expectancy.Muscular dystrophy was first described in the 1830s by Charles Bell. The word "dystrophy" comes from the Greek dys, meaning "no, un-" and troph- meaning "nourish".

Signs and symptoms

File:Gould Pyle 216.jpg|thumb|Severe limb deformities and contracturescontracturesThe signs and symptoms consistent with muscular dystrophy are:{{EMedicine|article|1259041|Muscular Dystrophy Clinical Presentation}}{hide}columns-list|colwidth=22em|

• 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

{edih}

Causes

The majority of muscular dystrophies are inherited; the different muscular dystrophies follow various inheritance patterns (X-linked, autosomal recessive or autosomal dominant). In a small percentage of patients, the disorder may have been caused by a de novo (spontaneous) mutation.WEB,weblink Muscular dystrophy - Causes - NHS Choices, Choices, NHS, www.nhs.uk, 2016-04-10, live,weblink" title="web.archive.org/web/20160402141504weblink">weblink 2016-04-02, BOOK, Griffiths, Anthony JF, Miller, Jeffrey H., Suzuki, David T., Lewontin, Richard C., Gelbart, William M., Spontaneous mutations, 2000,weblink {{page needed|date=January 2020}}

Diagnosis

The diagnosis of muscular dystrophy is based on the results of muscle biopsy, increased 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.WEB,weblink NIH /How is muscular dystrophy diagnosed?, 2015, NIH.gov, NIH, 10 April 2016, live,weblink 7 April 2016, 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.JOURNAL, Emery, Alan EH, 2002-02-23, The muscular dystrophies,weblink The Lancet, English, 359, 9307, 687–695, 10.1016/S0140-6736(02)07815-7, 0140-6736, 11879882, 31578361,

Classification{| class"wikitable"

! Disorder name!OMIM! Gene!Inheritance pattern!Age of onset!Muscles affected! Description|Becker muscular dystrophy300376none}}Dystrophin>DMDX-linked recessive inheritance>XR|Childhood|Distal limbs progressing to generalised weaknessDuchenne muscular dystrophy,May 2006 report to Congress {{webarchive>url=https://web.archive.org/web/20140405023440weblink|date=2014-04-05}} on Implementation of the MD CARE Act, as submitted by Department of Health and Human Service's National Institutes of Health affects predominantly boys.|Congenital muscular dystrophy| Multiple| MultipleAutosomal dominant inheritance>AD, 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.{{EMedicine|article|1180214|Congenital Muscular Dystrophy|clinical}}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.|Duchenne muscular dystrophy310200none}}Dystrophin>DMDX-linked recessive inheritance>XR|Childhood|Distal limbs progressing to generalised weakness, involving respiratory musclesWEBSITE=MEDLINEPLUS.GOVACCESS-DATE=2017-03-14ARCHIVE-URL=HTTPS://WEB.ARCHIVE.ORG/WEB/20170405014656/HTTPS://MEDLINEPLUS.GOV/ENCY/ARTICLE/000705.HTMWEBSITE=PATIENT.INFO ACCESS-DATE=2017-03-14 ARCHIVE-URL=HTTPS://WEB.ARCHIVE.ORG/WEB/20161202094502/HTTP://PATIENT.INFO/HEALTH/DUCHENNE-MUSCULAR-DYSTROPHY-LEAFLET, 2016-12-02, |Distal muscular dystrophy254130none}}Dysferlin>DYSFAutosomal dominant inheritance>AD, AR|20–60 years|Distal muscles in hands, forearms and lower legsCHAPTER=DISTAL MUSCULAR DYSTROPHIES VOLUME=101 YEAR=2011 DOI=10.1016/B978-0-08-045031-5.00016-5, 978-0-08-045031-5, 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.|Emery–Dreifuss muscular dystrophy|Multiple|MultipleX-linked recessive inheritance>XR, Autosomal dominant inheritance, Autosomal recessive inheritance>AR|Childhood, early teenage years|Distal limb muscles, limb-girdle, heartURL-STATUS=DEAD TITLE=OMIM ENTRY - # 310300 - EMERY-DREIFUSS MUSCULAR DYSTROPHY 1, X-LINKED; EDMD1 ACCESS-DATE=2017-03-14, HTTPS://GHR.NLM.NIH.GOV/CONDITION/EMERY-DREIFUSS-MUSCULAR-DYSTROPHY >TITLE=EMERY-DREIFUSS MUSCULAR DYSTROPHY - GENETICS HOME REFERENCE DATE=2017-03-07 URL-STATUS=LIVE ARCHIVE-DATE=2017-03-12, |Facioscapulohumeral muscular dystrophy158900none}}|DUX4Autosomal dominant inheritance>AD|Adolescence|Face, shoulders, upper arms, progressing to other musclesWEBSITE=GHR.NLM.NIH.GOV URL-STATUS=LIVE ARCHIVE-DATE=2017-03-24, Affected individuals can become severely disabled, with 20% requiring a wheelchair by age 50.STATLAND >FIRST1=JM FIRST2=R JOURNAL=CONTINUUM (MINNEAPOLIS, MINN.) VOLUME=22 PAGES=1916–1931 PMID=27922500WEBSITE=NLM.NIH.GOV ACCESS-DATE=2017-03-14 ARCHIVE-URL=HTTPS://WEB.ARCHIVE.ORG/WEB/20160704222205/HTTPS://WWW.NLM.NIH.GOV/MEDLINEPLUS/ENCY/ARTICLE/000707.HTM, 2016-07-04, |Limb–girdle muscular dystrophy| Multiple| MultipleAutosomal dominant inheritance>AD, AR|Any|Upper arms and legsTITLE=SPORTS SCIENCE HANDBOOK:I - Z.PUBLISHER=MULTI-SCIENCE PUBL. CO.ISBN=978-0906522-37-0, 121, |Myotonic muscular dystrophy160900none}}{{brk}}{{OMIM|none}}Myotonin-protein kinase>DMPK{{brk}}CNBPAutosomal dominant inheritance>AD|Adulthood|Skeletal muscles, heart, other muscle groupsmyotonia (delayed relaxation of muscles), as well as muscle wasting and weakness.TURNER LAST2=HILTON-JONES TITLE=THE MYOTONIC DYSTROPHIES: DIAGNOSIS AND MANAGEMENT VOLUME=81 PAGES=358–67 PMID=20176601 S2CID=2453622 DOI-ACCESS=FREE, Varies in severity and manifestations and affects many body systems in addition to skeletal muscles, including the heart, endocrine organs, and eyes.HTTPS://WWW.NCBI.NLM.NIH.GOV/BOOKS/NBK1165/>TITLE=MYOTONIC DYSTROPHY TYPE 1 - GENEREVIEWS® - NCBI BOOKSHELFACCESS-DATE=2017-03-14ARCHIVE-URL=HTTPS://WEB.ARCHIVE.ORG/WEB/20170118123627/HTTPS://WWW.NCBI.NLM.NIH.GOV/BOOKS/NBK1165/CHAPTER=MYOTONIC DYSTROPHY TYPE 1YEAR=1993LAST1=BIRD LAST2=ADAM LAST3=EVERMAN LAST4=MIRZAA LAST5=PAGON LAST6=WALLACE AUTHOR7=BEAN LJH FIRST8=K. W. FIRST9=A., |Oculopharyngeal muscular dystrophy164300none}}|PABPN1Autosomal dominant inheritance>AD, rarely AR|40–50 years|Eye muscles, face, throat, pelvis, shoulders|

Management

(File:Ankle Foot Orthosis leg brace worn on the left foot with ankle hinge.jpg|thumb|300px|Ankle foot orthosis)Currently, there is no cure for muscular dystrophy. In terms of management, physical therapy, occupational therapy, orthotic intervention (e.g., ankle-foot orthosis),WEB,weblink Muscular Dystrophy-OrthoInfo - AAOS, orthoinfo.aaos.org, 2016-04-10, live,weblink" title="web.archive.org/web/20160412104023weblink">weblink 2016-04-12, speech therapy, and respiratory therapy may be helpful.WEB,weblink What are the treatments for muscular dystrophy?, 2015, NIH.gov, NIH, 10 April 2016, live,weblink 7 April 2016, Low intensity corticosteroids such as prednisone, and deflazacort may help to maintain muscle tone.JOURNAL, McAdam, Laura C., Mayo, Amanda L., Alman, Benjamin A., Biggar, W. Douglas, The Canadian experience with long term deflazacort treatment in Duchenne muscular dystrophy, Acta Myologica, 2012, 31, 1, 16–20, 22655512, 3440807, Orthoses (orthopedic appliances used for support) and corrective orthopedic surgery may be needed to improve the quality of life in some cases. The cardiac problems that occur with Emery–Dreifuss muscular dystrophy (EDMD) and myotonic muscular dystrophy may require a pacemaker.JOURNAL, Verhaert, David, Richards, Kathryn, Rafael-Fortney, Jill A., Raman, Subha V., Cardiac Involvement in Patients With Muscular Dystrophies, Circulation: Cardiovascular Imaging, January 2011, 4, 1, 67–76, 10.1161/CIRCIMAGING.110.960740, 21245364, 3057042, The myotonia (delayed relaxation of a muscle after a strong contraction) occurring in myotonic muscular dystrophy may be treated with medications such as quinine.BOOK, Eddy, Linda L., Caring for Children with Special Healthcare Needs and Their Families: A Handbook for Healthcare Professionals, 2013, John Wiley & Sons, 978-1-118-51797-0, {{page needed|date=January 2020}}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.JOURNAL, 10.1177/1545968313496326, 23884013, Assisted Bicycle Training Delays Functional Deterioration in Boys with Duchenne Muscular Dystrophy, 2013, Jansen, Merel, Van Alfen, Nens, Geurts, Alexander C. H., De Groot, Imelda J. M., Neurorehabilitation and Neural Repair, 27, 9, 816–827, 9990910, 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.BOOK, R. M., Lehman, G. L., McCormack, 2001, Neurogenic and Myopathic Dysfunction, 802–3, Lorraine Williams, Pedretti, Mary Beth, Early, Occupational Therapy: Practice Skills for Physical Dysfunction, 5th, Mosby, 978-0-323-00765-8,

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.

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,JOURNAL, Laing, Nigel G, Davis, Mark R, Bayley, Klair, Fletcher, Sue, Wilton, Steve D, Molecular Diagnosis of Duchenne Muscular Dystrophy: Past, Present and Future in Relation to Implementing Therapies, The Clinical Biochemist Reviews, 2011, 32, 3, 129–134, 21912442, 3157948, French neurologist Guillaume Duchenne gave a comprehensive account of the most common and severe form of the disease, which now carries his name – Duchenne MD.WEB,weblink Muscular Dystrophy: Hope Through Research, 23 March 2020, National Institute of Neurological Disorders and Stroke, 7 April 2020,

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.JOURNAL, Berman, Ari,weblink The End of the Jerry Lewis Telethon—It's About Time, The Nation, 2011-09-02, 2017-03-14, On December 18, 2001, the MD CARE Act was signed into law in the US; it amends the Public Health Service Act to provide research for the various muscular dystrophies. This law also established the Muscular Dystrophy Coordinating Committee to help focus research efforts through a coherent research strategy.H.R. 717--107th Congress (2001) {{webarchive|url=https://web.archive.org/web/20120219184941weblink |date=2012-02-19 }}: MD-CARE Act, GovTrack.us (database of federal legislation), (accessed Jul 29, 2007)Public Law 107-84 {{webarchive|url=https://web.archive.org/web/20121107002224weblink |date=2012-11-07 }}, PDF as retrieved from NIH website

See also

{hide}columns-list|colwidth=30em|

• Fukuyama congenital muscular dystrophy
• Muscle hypertrophy
• Muscular Dystrophy UK
• Muscular Dystrophy Association (United States)
• Muscular Dystrophy Canada
• Spinal muscular atrophies

{edih}

References

{{Reflist}}

Further reading

• JOURNAL, De Los Angeles Beytía, Maria, Vry, Julia, Kirschner, Janbernd, Drug treatment of Duchenne musculardystrophy: available evidence and perspectives, Acta Myologica, 2012, 31, 1, 4–8, 22655510, 3440798,
• JOURNAL, Bertini, Enrico, D'Amico, Adele, Gualandi, Francesca, Petrini, Stefania, Congenital Muscular Dystrophies: A Brief Review, Seminars in Pediatric Neurology, December 2011, 18, 4, 277–288, 10.1016/j.spen.2011.10.010, 22172424, 3332154,

External links

{{Scholia|topic}}

• {{Curlie|/Health/Conditions_and_Diseases/Neurological_Disorders/Muscle_Diseases/Muscular_Dystrophies/|Muscular dystrophies}}

{{Medical resources| DiseasesDB =8C70}}G71.0}}359.0}}–{{ICD9|359.1}}| ICDO =| OMIM =| MedlinePlus = 001190| eMedicineSubj = orthoped| eMedicineTopic = 418| MeshID = D009136}}{{Muscular Dystrophy}}{{Diseases of myoneural junction and muscle}}{{Authority control}}