Authors' recommendations: Duchenne muscular dystrophy (DMD) and Becker muscular dystrophy (BMD) are neuromuscular diseases caused by variants in the dystrophin (DMD) gene, which is located on the X chromosome at band p21. Since DMD and BMD are inherited in an X-linked manner, the conditions primarily affect males (since they have only 1 X chromosome and therefore just 1 copy of the DMD gene). Most carrier females (who have 2 X chromosomes with 1 normal copy of DMD and 1 with a gene variant) are asymptomatic. The incidence of DMD and BMD in boys is approximately 1 in 3500 and 1 in 18,500, respectively. Dystrophin is a cytoskeletal protein that helps maintain muscle membrane stability. Variants in DMD are associated with 3 main disease presentations, DMD, BMD, and DMD-associated dilated cardiomyopathy (DCM). DMD typically presents from 2 to 5 years of age with waddling gait; difficulty running, jumping, and climbing; lumbar lordosis (increased curving of the spine); and calf hypertrophy (enlargement of the calf muscles). The weakness and wasting of the muscles are progressive and symmetrical, affecting the lower limbs and proximal muscles before the upper limbs and distal muscles. Joint contractures are also present early, later leading to asymmetric spinal deformities. Reduced mobility leads to decreased bone density and an increased risk of fractures. Boys with DMD are typically wheelchair-bound by 12 years of age. Cardiomyopathy is present in one-third of affected boys by 14 years of age, and in all by age 18. Many boys with DMD also have nonprogressive cognitive impairment characterized by deficits in working memory and executive function. Most affected men die in their 20s, usually due to respiratory complications and less frequently DCM. BMD is characterized by similar muscle wasting and weakness; however, the onset is later, from adolescence to adulthood, with most men remaining ambulatory at least into their 20s. BMD displays a wider range of clinical presentation than DMD. Heart failure from DCM is the most common cause of death and usually occurs in the 40s or 50s. Cognitive impairment is less frequent in BMD and, if present, less severe than in DMD. The distinction between DMD and BMD is typically based on the age of wheelchair dependency, with BMD wheelchair dependency occurring after age 16. DMD-associated DCM is characterized by left ventricular dilation and congestive heart failure. There is no cure for DMD or BMD with primarily symptomatic treatment to improve quality of life and impact survival. Studies suggest a positive impact of corticosteroids (in slowing the decline in muscle strength and function in DMD); other treatments include pharmacologic interventions, cardiac medical therapy, pulmonary ventilation, nutrition management, orthesis (device used in orthopedics such as a brace), physical therapy, psychosocial support, and surgery for tendon retractions and scoliosis. There are ongoing clinical trials for genetic approaches to decrease disease severity.

Project Status: Completed

Year Published: 2014

URL for published report: The report may be purchased from: http://www.hayesinc.com/hayes/crd/?crd=17263

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: United States

Organisation Name: HAYES, Inc.

Contact Address: 157 S. Broad Street, Suite 200, Lansdale, PA 19446, USA. Tel: 215 855 0615; Fax: 215 855 5218

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Contact Email: saleinfo@hayesinc.com

Copyright: 2014 Winifred S. Hayes, Inc