Duchenne and Becker Muscular Dystrophy - Description

Page Contents

• Other Names
• ICD-9
• Description
• Genetics
• Prognosis
• Prevalence
• Pearls And Alerts
• Helpful Articles

Other Names

dystrophinopathy (Duchenne, Becker, and Intermediate muscular dystrophies are somewhat arbitrary categories of dystrophinopathy)
pseudohypertrophic muscular dystrophy

ICD-9

359.1, hereditary progressive muscular dystrophy

For additional ICD9 codes for associated conditions, see DMD-ICD9 ( 65 KB) .

Description

Duchenne (DMD), Becker (BMD), and Intermediate (IMD) muscular dystrophy represent varying clinical presentations of an X-linked, progressive symmetric muscle weakness caused by a relative or absolute absence of dystrophin, a muscle protein. The weakness, which is greater proximally than distally, occurs because muscles are gradually replaced with fatty connective tissue (see Muscle biopsy images, DMD (Wash U)). DMD refers to the earliest, and most severe presentation; BMD to presentation later in childhood; and IMD to cases intermediate in severity between DMD and BMD.

Boys with DMD will present in the preschool years with muscle weakness, difficulty walking, and large calves. The weakness worsens over the subsequent few years, resulting in inability to ambulate by 8 to 13 years of age. Treatment with steroids can prolong the ability to walk by several years. Muscle weakness continues to progress and respiratory weakness leads to difficulty breathing. Susceptibility to respiratory infection and progressive deterioration of pulmonary function generally lead to premature death, usually in the twenties. Cardiomyopathy may also occur and is generally progressive. With steroid treatment and proactive care of heart and lungs, affected boys should be able to walk and live longer. Orthopedic manifestations of DMD, such as toe-walking, contractures of the ankles, knees, and hips, and scoliosis, are common. Bowel and bladder function are often mildly affected, with constipation and urinary urgency being frequent symptoms. Mild to moderate developmental delay is common but not universal.

Boys with BMD will present with weakness later in childhood, adolescence, or even young adulthood. Progression is much slower and life expectancy is longer. Cardiac problems are common in boys and adults with BMD.

Genetics

DMD, BMD, and IMD are X-linked and caused by mutations in the gene for dystrophin, which is very large and there are many possible mutations, including various deletions, duplications, and point mutations. Some are more common than others. Although some mutations are known to be associated with a milder (Becker-like) or more severe (Duchenne-like) phenotype, this is not true of all the known mutations. [Flanigan: 2009] Because of the complex genetics of the disease and that one third of cases are thought to be due to new mutations, there is often no family history of DMD. See the Genetics of Duchenne muscular dystrophy, Dystrophinopathies (GeneReviews), and Muscular dystrophy, Duchenne type (OMIM).

Prognosis

Boys with DMD usually become non-ambulatory by 12 years of age and die in their mid-twenties of respiratory complications. Treatment with steroids starting in early childhood improves life expectancy, as does comprehensive, proactive medical care. Individuals with BMD often walk into their thirties and life expectancy is longer, often into the 40s or later. Up to 50% of individuals with BMD die of cardiac complications. Cardiac death is less common in individuals with DMD (20%), but likely to become more common as pulmonary complications are increasingly prevented. [Darras: 2008]

Prevalence

DMD occurs in approximately 1 in 3,500 male births. It is the most common X-linked disease, occurring only in males (although there are occasional female carriers who demonstrate some manifestations). It is also the most common childhood muscular dystrophy. [Dubowitz: 1995] BMD and IMD are much less common; differences in definitions of these clinical presentations make prevalence data problematic.

Pearls And Alerts

Helpful Articles

PubMed search on Duchenne muscular dystrophy: review articles over the last 5 years

Bushby K, Bourke J, Bullock R, Eagle M, Gibson M, and Quinby J.
The multidisciplinary management of Duchenne muscular dystrophy.
Current Paediatrics. 2005;15:292-300. / Full Text

Duchenne and Becker Muscular Dystrophy Module Authors

The authors listed above are responsible for the overall Duchenne and Becker Muscular Dystrophy Module. Authors contributing to individual pages in the module are listed on those pages.

Page Bibliography

Darras, BT, Korf, BR, and Urion, DK.
Dystrophinopathies.
GeneReviews (NIH); (2008) http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=dbmd.

Dubowitz, Victor.
Muscle Disorders in Childhood.
2nd ed. London: W.B. Saunders Company Ltd; 1995. 0702-014370
This reference focuses on the clinical assessment, diagnosis, management, and prognosis of all forms of muscle diseases that affect children. Includes a readable account of relevant genetics, biochemistry, and molecular biology, in addition to numerous case histories.

Flanigan KM, Dunn DM, von Niederhausern A, Soltanzadeh P, Gappmaier E, Howard MT, Sampson JB, Mendell JR, Wall C, King WM, Pestronk A, Florence JM, Connolly AM, Mathews KD, Stephan CM, Laubenthal KS, Wong BL, Morehart PJ, Meyer A, Finkel RS, Bonnemann CG, Medne L, Day JW, Dalton JC, Margolis MK, Hinton VJ, Weiss RB.
Mutational spectrum of DMD mutations in dystrophinopathy patients: application of modern diagnostic techniques to a large cohort.
Hum Mutat. 2009;30(12):1657-66. PubMed abstract