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Becker Muscular Dystrophy (BMD)

Signs and Symptoms

The pattern of muscle loss in BMD usually begins with the hips and pelvic area, the thighs, and the shoulders. To compensate for weakening muscles, a person with BMD may walk with a waddling gait, walk on his toes, or stick out his abdomen. The onset of symptoms may vary from 5 to 60 years of age.1

The rate of muscle degeneration varies a great deal from one person to another. Typically, patients with BMD maintain the ability to walk at least until age 16 and mostly well through adult life.

Pain and sensation

Because muscular dystrophy doesn’t affect nerves directly, touch and other senses remain normal, as does control over the smooth, or involuntary, muscles of the bladder and bowel, and sexual functions.

Muscle deterioration in BMD usually is not painful in itself. Some people report muscle cramps at times; these usually can be treated with over-the-counter pain relievers.

The heart

Like muscles in the limbs, heart muscles also can be weakened by lack of dystrophin. Most  patients diagnosed with BMD develop cardiomyopathy — heart muscle weakness — because of a deficiency of dystrophin. The muscle layer (myocardium) of the heart deteriorates, just as the skeletal muscles do.

Most patients diagnosed with BMD show muscle weakness as their initial symptoms, before they present cardiac symptoms. However, there are rare cases in scientific literature of patients presenting cardiac symptoms first.2,3

Eclectrocardiology reveals cardiac involvement in 60% to 70% of BMD patients and, sometimes, it can be a predominant feature of the disease. All four of the heart’s chambers are involved in fibrosis, and heart failure can rapidly progress.4,5

Damage done by BMD to the heart can become life-threatening as early as the teen years. Some people with BMD have mild skeletal muscle involvement but severe cardiac problems. It has been suggested that, as patients with BMD remain able to perform strenuous exercise, this high physical activity may be harmful for the cardiac muscle cells with the abnormal dystrophin. For these reasons, everyone with BMD should be monitored by a cardiologist. See the Medical Management section for more information on managing heart problems in BMD.

To view a presentation by cardiologist Elizabeth McNally about the heart in BMD, see the August 2012 video Cardiac Complications and Management in BMD.

Breathing and coughing

Respiratory muscles often stay strong in BMD for many years, but eventually, they may become weaker than is optimal for breathing and coughing (to clear secretions from the respiratory tract).

To view a presentation by pulmonary medicine specialist Lisa Wolfe at Northwestern University in Chicago, see the August 2012 video Lung Health in Neuromuscular Disease.

Cognition

Doctors believe that dystrophin abnormalities in the brain may cause cognitive and behavioral deficits and other neuropsychiatric disturbances.6 Intellectual disability or cognitive impairment are not common or severe in patients diagnosed with BMD in comparison to those diagnosed with DMD. About 10% of patients have an IQ lower than 70.7,8 For more on coping with intellectual effects, see Medical Management.

References

  1. Bradley, W. G., Jones, M. Z., Mussini, J. -M & Fawcett, P. R. W. Becker-type muscular dystrophy. Muscle Nerve (1978). doi:10.1002/mus.880010204
  2. Ho, R., Nguyen, M.-L. & Mather, P. Cardiomyopathy in becker muscular dystrophy: Overview. World J. Cardiol. (2016). doi:10.4330/wjc.v8.i6.356
  3. Ruiz-Cano, M. J. et al. Successful heart transplantation in patients with inherited myopathies associated with end-stage cardiomyopathy. Transplant. Proc. (2003). doi:10.1016/S0041-1345(03)00515-3
  4. Melacini, P. et al. Myocardial involvement is very frequent among patients affected with subclinical Becker’s muscular dystrophy. Circulation (1996). doi:10.1161/01.CIR.94.12.3168
  5. Yazawa, M. et al. A family of becker’s progressive muscular dystrophy with severe cardiomyopathy. Eur. Neurol. (1987). doi:10.1159/000116122
  6. Ricotti, V. et al. Neurodevelopmental, emotional, and behavioural problems in Duchenne muscular dystrophy in relation to underlying dystrophin gene mutations. Dev. Med. Child Neurol. (2016). doi:10.1111/dmcn.12922
  7. Bushby, K. M. D. & Gardner-Medwin, D. The clinical, genetic and dystrophin characteristics of Becker muscular dystrophy - I. Natural history. J. Neurol. (1993). doi:10.1007/BF00858725
  8. Daoud, F. et al. Analysis of Dp71 contribution in the severity of mental retardation through comparison of Duchenne and Becker patients differing by mutation consequences on Dp71 expression. Hum. Mol. Genet. (2009). doi:10.1093/hmg/ddp320

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