What is Muscular Dystrophy?

Man in a wheelchair reading his laptop

Muscular dystrophies are a group of diseases caused by defects in a person’s genes. Over time, this muscle weakness decreases mobility and makes the tasks of daily living difficult. There are many muscular dystrophies and the Centers for Disease Control and Prevention (CDC) studies the major types.

Different types of muscular dystrophy affect specific groups of muscles, have a specific age when signs and symptoms are first seen, vary in how severe they can be, and are caused by imperfections in different genes. Muscular dystrophy can run in the family, or a person might be the first one in their family to have the condition.

Muscular dystrophy is rare, and there is not a lot of data on how many people are affected by the condition. Much of the information comes from outside the United States. CDC scientists are working to estimate the number of people with each type of muscular dystrophy in the United States. The table below shows what is known about the major types of muscular dystrophy.

Types of Muscular Dystrophy

How common is this type?
In 2007, 349 out of 2.37 million males aged 5-24 years were reported to have DMD or BMD in the United States.1  This means that about 15 out of every 100,000 males ages 5-24 years were affected that year.

In 2009, 233 out of 1.49 million males were reported to have DMD or BMD in Northern England.2  That is, about 16 out of every 100,000 males were affected that year.

Are males or females more likely to be affected?
Males

When does muscle weakness typically begin?
DMD: Before 5 years
BMD: Between 7-12 years

Which muscles usually show weakness first?
Upper arms, upper legs

What other parts of the body can be affected?
Brain, throat, heart, diaphragm/chest muscles, stomach, intestines, spine

For more information, please see the summary provided by the National Institutes of Health on Duchenne/Becker Muscular DystrophyExternal

References:

1. Emery AEH. The muscular dystrophies.External The Lancet. 2002 Feb 23 2002;359(9307):687-695. 

2. Bushby KM, Goodship JA, Nicholson LV, Johnson MA, Haggerty ID, Gardner-Medwin D. Variability in clinical, genetic and protein abnormalities in manifesting carriers of Duchenne and Becker muscular dystrophyExternal. Neuromuscul. Disord. Jan 1993;3(1):57-64.

3. Bushby KM, Appleton R, Anderson LV, Welch JL, Kelly P, Gardner-Medwin D. Deletion status and intellectual impairment in Duchenne muscular dystrophy.External Dev. Med. Child Neurol. Mar 1995;37(3):260-269.

4. Centers for Disease C, Prevention. Prevalence of Duchenne/Becker muscular dystrophy among males aged 5-24 years – four states, 2007. MMWR Morb. Mortal. Wkly. Rep. Oct 16 2009;58(40):1119-1122.

5. Norwood FL, Harling C, Chinnery PF, Eagle M, Bushby K, Straub V. Prevalence of genetic muscle disease in Northern England: in-depth analysis of a muscle clinic populationExternal. Brain. Nov 2009;132(Pt 11):3175-3186.

How common is this type?
In 2009, 316 out of 2.99 million individuals of all ages were reported to have MMD in Northern England.1  This means that about 11 out of every 100,000 people were affected that year.

Are males or females more likely to be affected?
Males and females equally

When does muscle weakness typically begin?
Between 10-30 years, but ranges from birth to 70 years

Which muscles usually show weakness first?
Face, neck, arms, hands, hips, lower legs

What other parts of the body can be affected?
Eyes, throat, heart, stomach, intestines, hormone-producing organs, nerves, skin

For more information, please see the summary provided by the National Institutes of Health on Myotonic DystrophyExternal

References:

1. Norwood FL, Harling C, Chinnery PF, Eagle M, Bushby K, Straub V. Prevalence of genetic muscle disease in Northern England: in-depth analysis of a muscle clinic populationExternal. Brain. Nov 2009;132(Pt 11):3175-3186.

2. Turner C, Hilton-Jones D. The myotonic dystrophies: diagnosis and management.External J. Neurol. Neurosurg. Psychiatry. Apr 2010;81(4):358-367.

3. Gharehbaghi-Schnell EB, Finsterer J, Korschineck I, Mamoli B, Binder BR. Genotype-phenotype correlation in myotonic dystrophyExternal. Clin. Genet. Jan 1998;53(1):20-26.

4. New nomenclature and DNA testing guidelines for myotonic dystrophy type 1 (DM1)External. The International Myotonic Dystrophy Consortium (IDMC). Neurology. Mar 28 2000;54(6):1218-1221.

5. Harper PS. Myotonic Dystrophy. Vol 37. 3 ed. London: W.B. Saunders; 2001.

6. Moxley RT, Pandya S, Ciafaloni E, Fox DJ, Campbell K. Change in Natural History of Duchenne Muscular Dystrophy With Long-term Corticosteroid Treatment: Implications for ManagementExternal. J. Child Neurol. September 1, 2010 2010;25(9):1116-1129.

7. Moxley RT MG. The Myotonic Dystrophies. In: Rosenberg RN DS, Paulson HL, Ptacek L, Nestler EJ, ed. The Molecular and Genetic Basis of Neurologic and Psychiatric Disease. Philadelphia, PA: Wolters Kluwer; 2008:532-541.

How common is this type? 
In 2009, 68 out of 2.99 million individuals of all ages were reported to have LGMD in Northern England.1  This means that about 2 out of every 100,000 people were affected that year.

Are males or females more likely to be affected?
Males and females equally

When does muscle weakness typically begin?
Ranges from early childhood to late adulthood

Which muscles usually show weakness first?
Shoulders, hips

What other parts of the body can be affected?
Heart, diaphragm/chest muscles, spine

For more information, please see the summary provided by the National Institutes of Health on Limb-Girdle Muscular DystrophyExternal

References:

1. Norwood FL, Harling C, Chinnery PF, Eagle M, Bushby K, Straub V. Prevalence of genetic muscle disease in Northern England: in-depth analysis of a muscle clinic populationExternal. Brain. Nov 2009;132(Pt 11):3175-3186.

2. Emery AEH. The muscular dystrophies.External The Lancet. 2002 Feb 23 2002;359(9307):687-695.

3. Guglieri M, Straub V, Bushby K, Lochmuller H. Limb-girdle muscular dystrophies.External Curr. Opin. Neurol. Oct 2008;21(5):576-584.

4. Mathews KD, Moore SA. Limb-girdle muscular dystrophy.External Curr. Neurol. Neurosci. Rep. Jan 2003;3(1):78-85.

How common is this type? 
In 2009, 118 out of 2.99 million individuals of all ages were reported to have FSH in Northern England.5  This means that about 4 out of every 100,000 people were affected that year.

Are males or females more likely to be affected? 
Males and females equally

When does muscle weakness typically begin?
By 20 years  (average age in the teens)

Which muscles usually show weakness first?
Face, shoulders, upper arms, lower legs

What other parts of the body can be affected?
Eyes, ears, heart, trunk

For more information, please see the summary provided by the National Institutes of Health on Facioscapulohumeral Muscular DystrophyExternal

References:

1. Norwood FL, Harling C, Chinnery PF, Eagle M, Bushby K, Straub V. Prevalence of genetic muscle disease in Northern England: in-depth analysis of a muscle clinic populationExternal. Brain. Nov 2009;132(Pt 11):3175-3186.

2. Emery AEH. The muscular dystrophies.External The Lancet. 2002 Feb 23 2002;359(9307):687-695.

3. Awerbuch GI, Nigro MA, Wishnow R. Beevor’s sign and facioscapulohumeral dystrophyExternal. Arch. Neurol. Nov 1990;47(11):1208-1209.

4. Tawil R, Van Der Maarel SM. Facioscapulohumeral muscular dystrophyExternal. Muscle Nerve. Jul 2006;34(1):1-15.

How common is this type?
In 2009, 68 out of 2.99 million individuals of all ages were reported to have CMD in Northern England.1  This means that about 2 out of every 100,000 people were affected that year.

Are males or females more likely to be affected?
Males and females equally

When does muscle weakness typically begin? 
At birth or in early infancy

Which muscles usually show weakness first? 
Neck, arms, trunk, legs

What other parts of the body can be affected?
Brain, eyes, throat, heart, diaphragm/chest muscles, nerves, spine

For more information, please see the summary provided by the National Institutes of Health on Congenital Muscular Dystrophy (Fukuyama typeExternal, Ullrich typeExternal, and others)

References:

1. Norwood FL, Harling C, Chinnery PF, Eagle M, Bushby K, Straub V. Prevalence of genetic muscle disease in Northern England: in-depth analysis of a muscle clinic populationExternal. Brain. Nov 2009;132(Pt 11):3175-3186.

2. Reed UC. Congenital muscular dystrophy. Part I: a review of phenotypical and diagnostic aspectsExternal. Arq. Neuropsiquiatr. Mar 2009;67(1):144-168.

3. Wang CH, Dowling JJ, North K, et al. Consensus statement on standard of care for congenital myopathiesExternal. J. Child Neurol. Mar 2012;27(3):363-382.

4. Bertini E, D’Amico A, Gualandi F, Petrini S. Congenital muscular dystrophies: a brief reviewExternal. Semin. Pediatr. Neurol. Dec 2011;18(4):277-288.

How common is this type?
In 2009, 10 out of 2.99 million individuals of all ages were reported to have DD in Northern England.1  This means less than 1 out of every 100,000 people were affected that year.

Are males or females more likely to be affected?
Males and females equally

When does muscle weakness typically begin?
Ranges from late teens to adulthood

Which muscles usually show weakness first?
Lower arms, hands, lower legs, feet

What other parts of the body can be affected?
Nerves, other muscles, depending on the type of DD

For more information, please see the summary provided by the National Institutes of Health on Distal Muscular Dystrophy (LaingExternal, type 2External, tibial typeExternal, and others)

References:

1. Norwood FL, Harling C, Chinnery PF, Eagle M, Bushby K, Straub V. Prevalence of genetic muscle disease in Northern England: in-depth analysis of a muscle clinic populationExternal. Brain. Nov 2009;132(Pt 11):3175-3186.

2. Emery AEH. The muscular dystrophies.External The Lancet. 2002 Feb 23 2002;359(9307):687-695.

3. Udd B. Distal muscular dystrophies. Handbook of clinical neurology. 2011;101:239-262.

4. Nonaka I. Distal myopathiesExternal. Curr. Opin. Neurol. Oct 1999;12(5):493-499.

How common is this type?
In 2009, 4 out of 2.99 million individuals of all ages were reported to have OPMD in Northern England.1  This means that less than 1 out of every 100,000 people were affected that year.

Are males or females more likely to be affected?
Males and females equally

When does muscle weakness typically begin?
After 40 years

Which muscles usually show weakness first?
Face (mostly around the eyes), neck, upper arms, upper legs

What other parts of the body can be affected?
Throat

For more information, please see the summary provided by the National Institutes of Health on Oculopharyngeal Muscular DystrophyExternal

References:
1. Emery AEH. The muscular dystrophies.External The Lancet. 2002 Feb 23 2002;359(9307):687-695.

2. Norwood FL, Harling C, Chinnery PF, Eagle M, Bushby K, Straub V. Prevalence of genetic muscle disease in Northern England: in-depth analysis of a muscle clinic populationExternal. Brain. Nov 2009;132(Pt 11):3175-3186.

3. Ruegg S, Lehky Hagen M, Hohl U, et al. Oculopharyngeal muscular dystrophy – an under-diagnosed disorder?External Swiss Med. Wkly. Oct 1 2005;135(39-40):574-586.

4. Bouchard JP, Brais B, Brunet D, Gould PV, Rouleau GA. Recent studies on oculopharyngeal muscular dystrophy in QuebecExternal. Neuromuscul. Disord. Oct 1997;7 Suppl 1:S22-29

5. Brais B. Oculopharyngeal muscular dystrophy. Handbook of clinical neurology. 2011;101:181-192

How common is this type?
In 2009, 4 out of 2.99 million individuals of all ages were reported to have EDMD in Northern England.1  This means that less than 1 out of every 100,000 people were affected that year.

Are males or females more likely to be affected?
Males

When does muscle weakness typically begin?
Between 5-15 years

Which muscles usually show weakness first? 
Upper arms, lower legs

What other parts of the body can be affected?
Heart, spine

For more information, please see the summary provided by the National Institutes of Health on Emery-Dreifuss Muscular DystrophyExternal

References:

1. Norwood FL, Harling C, Chinnery PF, Eagle M, Bushby K, Straub V. Prevalence of genetic muscle disease in Northern England: in-depth analysis of a muscle clinic populationExternal. Brain. Nov 2009;132(Pt 11):3175-3186.

2. Emery AE. Emery-Dreifuss muscular dystrophy – a 40 year retrospectiveExternal. Neuromuscul. Disord. Jun 2000;10(4-5):228-232.

3. Miller RG, Layzer RB, Mellenthin MA, Golabi M, Francoz RA, Mall JC. Emery-Dreifuss muscular dystrophy with autosomal dominant transmissionExternal. Neurology. Aug 1985;35(8):1230-1233.

Connect with an organization focused on the type of muscular dystrophy that affects you or someone in your family.

Read about CDC’s Muscular Dystrophy Surveillance Tracking and Research Network, known as MD STARnet. Learn more about CDC’s other muscular dystrophy projects.