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. Mobility problems are usually noticed by age 15.²

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 living with BMD report muscle cramps and pain with strenuous physical activity.³

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.^4,5,6

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.^7,8

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. 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 Dr. Barry Byrne about the cardiac involvement in BMD, see the video Becker Muscular Dystrophy and Cardiac Involvement.

Breathing and coughing

Respiratory muscles often stay strong in BMD for many years, but eventually, the diaphragm and other respiratory muscles can weaken resulting in difficulties for breathing and coughing. A 2021 natural history study of respiratory function in adults with BMD found that patients experienced a loss in breathing function over time and showed that the decline accelerated significantly after loss of ambulation.⁹ The study highlights the need for careful monitoring of respiratory function in BMD patients, particularly in those who have lost the ability to walk independently.

Individuals with BMD should work with a respiratory specialist to regularly monitor their breathing function. Medical equipment may be needed as the condition progresses.

To view a presentation on specialized care in BMD by neurologist Dr. Hoda Abdel-Hamid from the Children’s Hospital of Pittsburgh, see the video Care Considerations in Becker Muscular Dystrophy.

Cognition

Doctors believe that dystrophin abnormalities in the brain may cause cognitive and behavioral deficits and other neuropsychiatric disturbances.¹⁰ People with BMD might have higher rates of autism, attention-deficit/hyperactivity disorder (ADHD), depression, anxiety, or obsessive-compulsive disorder (OCD) compared to the general population.^11,12 It's important to assess these cognitive and emotional issues when diagnosing BMD. If a person with BMD has trouble in school, they should also be evaluated for cognitive issues. These evaluations should be done by a neuropsychologist, a specialist trained to assess mental and cognitive functions, using tests that look at social skills, emotional well-being, and behavior.

Natural history of BMD

Few studies have tracked the long-term progression of BMD over time.^13,14 Findings from a 3-year longitudinal natural history study, published in 2024,¹⁴ found that certain mutations in the dystrophin gene (deletion mutations in dystrophin exons 45–47 or 45–48) were most common in people with BMD. Disease progression was highly variable, though progression of some specific outcomes was influenced by age and mutation groups. Importantly, the study found that most of the disease progression in BMD occurs in adulthood. Breathing function was found to decline over the lifespan, while motor functions were generally stable until later ages, when these functions declined.¹⁴

Outcome measures for BMD

Natural history studies help to better understand how diseases like BMD progress. This understanding can improve patient care and help with the design of clinical trials.

Natural history studies detail long-term changes in functional abilities of affected people. Using these documented changes in functional abilities (also known outcome measures) for comparison, researchers can evaluate treatment effects and determine who qualifies for trials and how many participants are needed.

The North Star Ambulatory Assessment (NSAA) and North Star Assessment for Limb-Girdle muscular dystrophies (NSAD) are two outcome measures used to track changes in functional abilities over time in people with BMD.¹³ Decreases in NSAA and NSAD scores denote the progression of BMD, which is evident through the sequential loss of abilities. Some functions, like standing from a chair, are affected earlier, while others, like lifting the head, decline later, compared to Duchenne muscular dystrophy (DMD). This information is crucial for designing meaningful clinical trials and understanding the significance of changes in clinical outcomes for BMD, a serious condition with no approved treatments.

Studies have aimed to identify the best outcome measures for future clinical trials in BMD. One study assessed BMD patients using muscle magnetic resonance imaging (MRI), patient-reported outcomes, and various clinical tests for motor function and muscle strength. This study found MRI measurement of fat in thigh muscles as a good way to track muscle changes in BMD patients, and identified the 32-item Motor Function Measurement (MFM-32) as the best assessment to detect changes in muscle function in adults with BMD.¹⁵

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. What is Becker Muscular Dystrophy: https://www.mda.org/sites/default/files/2021/07/BMD_FactSheet_Jun2021.pdf. Published June, 2021. Accessed October 28, 2023.
3. Magot A, Wahbi K, Leturcq F, Jaffre S, Péréon Y, Sole G; French BMD working group. Diagnosis and management of Becker muscular dystrophy: the French guidelines. J Neurol. 2023 Oct;270(10):4763-4781. doi: 10.1007/s00415-023-11837-5. Epub 2023 Jul 9. PMID: 37422773.
4. Ho, R., Nguyen, M.-L. & Mather, P. Cardiomyopathy in becker muscular dystrophy: Overview. World J. Cardiol. (2016). doi:10.4330/wjc.v8.i6.356
5. 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
6. Finsterer J, Stöllberger C. Cardiac involvement in Becker muscular dystrophy. Can J Cardiol. 2008 Oct;24(10):786-92. doi: 10.1016/s0828-282x(08)70686-x. PMID: 18841259; PMCID: PMC2643160.
7. 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
8. Yazawa, M. et al. A family of becker’s progressive muscular dystrophy with severe cardiomyopathy. Eur. Neurol. (1987). doi:10.1159/000116122
9. De Wel B, Willaert S, Nadaj-Pakleza A, Aubé-Nathier AC, Testelmans D, Buyse B, Claeys KG. Respiratory decline in adult patients with Becker muscular dystrophy: A longitudinal study. Neuromuscul Disord. 2021 Mar;31(3):174-182. doi: 10.1016/j.nmd.2020.12.010. Epub 2020 Dec 26. PMID: 33454189.
10. 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
11. Pascual-Morena C, Cavero-Redondo I, Reina-Gutiérrez S, Saz-Lara A, López-Gil JF, Martínez-Vizcaíno V. Prevalence of Neuropsychiatric Disorders in Duchenne and Becker Muscular Dystrophies: A Systematic Review and Meta-analysis. Arch Phys Med Rehabil. 2022 Dec;103(12):2444-2453. doi: 10.1016/j.apmr.2022.05.015. Epub 2022 Jul 15. PMID: 35839922.
12. Pascual-Morena C, Martínez-Vizcaíno V, Saz-Lara A, López-Gil JF, Fernández-Bravo-Rodrigo J, Cavero-Redondo I. Epileptic disorders in Becker and Duchenne muscular dystrophies: a systematic review and meta-analysis. J Neurol. 2022 Jul;269(7):3461-3469. doi: 10.1007/s00415-022-11040-y. Epub 2022 Mar 1. PMID: 35229191.
13. Bello L, Campadello P, Barp A, Fanin M, Semplicini C, Sorarù G, Caumo L, Calore C, Angelini C, Pegoraro E. Functional changes in Becker muscular dystrophy: implications for clinical trials in dystrophinopathies. Sci Rep. 2016 Sep 1;6:32439. doi: 10.1038/srep32439. PMID: 27582364; PMCID: PMC5007528.
14. Clemens PR, Gordish-Dressman H, Niizawa G, Gorni K, Guglieri M, Connolly AM, Wicklund M, Bertorini T, Mah J, Thangarajh M, Smith EC, Kuntz NL, McDonald CM, Henricson E, Upadhyayula S, Byrne B, Manousakis G, Harper A, Iannaccone S, Dang UJ. Findings from the Longitudinal CINRG Becker Natural History Study. J Neuromuscul Dis. 2024;11(1):201-212. doi: 10.3233/JND-230178. PMID: 37980682; PMCID: PMC10789327.
15. De Wel B, Iterbeke L, Huysmans L, Peeters R, Goosens V, Dubuisson N, van den Bergh P, Van Parijs V, Remiche G, De Waele L, Maes F, Dupont P, Claeys KG. Lessons for future clinical trials in adults with Becker muscular dystrophy: Disease progression detected by muscle magnetic resonance imaging, clinical and patient-reported outcome measures. Eur J Neurol. 2024 Jul;31(7):e16282. doi: 10.1111/ene.16282. Epub 2024 Mar 20. PMID: 38504654; PMCID: PMC11235693.

Last update: September 2024
Reviewed by Sumit Verma, MD; Emory University School of Medicine