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Health and Disease

Muscular Dystrophy (MD): About the Conditions Centered Around Muscle Weakness

Muscular dystrophy is a group of rare conditions that causes progressive muscle weakness and degeneration. It most commonly affects young boys, but it can affect others of any age as well.

By Michelle Li

Published 10:41 PM EST, Wed March 10, 2021

Introduction

Muscular dystrophy (MD) is a group of conditions that causes muscle weakness and degeneration. It is an inherited disorder in which symptoms gradually worsen over time (Quercia). Age of onset varies depending on the type of muscular dystrophy, ranging from childhood to the later stages of life. The severity, rate of progression, and pattern of affected muscles also vary with the type of MD. Many individuals with muscular dystrophy lose the ability to walk and, unfortunately, live shorter lives than average due to the condition (“Muscular Dystrophy: Hope in Research”). There are no cures for any forms of muscular dystrophy, but treatments such as physical therapy and braces aim to improve muscle function and slow deterioration.

The first reported case of muscular dystrophy in the 1830s was of two brothers that were experiencing progressive muscle weakness that began around age 10. They developed general weakness and muscle damage, and it was observed that the damaged muscle tissue was replaced with fat and connective tissue. At the time, it was mistakenly thought that these were symptoms of tuberculosis. In the years that followed, more cases of boys developing muscle weakness and dying at an early age were reported. As more cases were studied and observed, the different types of muscular dystrophy were classified, and its genetic link was discovered (“Muscular Dystrophy: Hope in Research”).

Types of Muscular Dystrophy

Duchenne muscular dystrophy (DMD) was named after Guillaume Duchenne, a French neurologist who gave a detailed account of 13 boys with the disorder in the 1860s (“Muscular Dystrophy: Hope in Research”). Duchene muscular dystrophy is the most common—accounting for 50% of MD cases—and the most severe type of muscular dystrophy. It affects one in every 3,500 males (Bosworth). It most commonly affects young boys and is much rarer for females. Symptoms begin to appear in the early toddler years and become apparent with difficulty walking, an affected gait, loss of reflexes, frequent falls, etc. Progressive muscle-weakening begins in the legs before spreading to the upper arms. This results in the loss of the ability to walk and often the use of a wheelchair by early adolescence. Those with DMD also experience muscle wasting, a decrease in muscle mass and strength due to lack of physical activity. Eventually, the cardiac muscles are weakened, which leads to breathing problems and fatal infections. The average life expectancy of individuals with DMD is the late teens or early twenties, but this has improved significantly with some living in their 30s and 40s (Bosworth).

Becker muscular dystrophy shares some similarities with Duchenne MD but is less severe. It affects one in every 30,000 males with most experiencing symptoms at 11 years old to as late as 25 years old (Bosworth). Similar to Duchenne muscular dystrophy, a symmetrical progression of muscle weakness is usually noticed in the upper arms, legs, and pelvis. The rate of progression is slower than that of DMD, so some retain the ability to walk until their mid-thirties or never need to use a wheelchair. Cardiac complications are also often fatal for those with Becker MD, although the average life expectancy is the mid-forties (Bosworth).

Emery-Dreifuss muscular dystrophy also develops in children, most commonly boys, at a young age. Compared to Duchenne muscular dystrophy, they experience slower and less severe muscle weakness in their arms and legs. Prior to significant muscle weakness, those with Emery-Dreifuss MD also experience contractures—tightening of muscles that prevent normal movement—in the spine, neck, elbows, knees, and ankles; this results in locked elbows or rigid spines (“Muscular Dystrophy: Hope in Research”).

Limb-girdle muscular dystrophy affects both males and females with symptoms appearing in late childhood to early adulthood. Individuals experience muscle weakness and wasting of the muscles around the hip and shoulder areas, known as the limb-girdle area; this spreads to the neck and legs. They may have difficulty rising from chairs or have an affected gait. Different types of Limb-girdle MD have also been identified with different rates of progression and severity, ranging from symptoms that develop slowly and interfere minimally with life to more severe muscle damage and inability to walk (“Muscular Dystrophy: Hope in Research”).

Facioscapulohumeral muscular dystrophy also develops in both males and females beginning in late childhood to early adulthood. It affects about one in every 20,000 people (Quercia). This type of muscular dystrophy causes asymmetric muscle weakness in the face, shoulders, and upper arms. Muscles around the eyes and ears are commonly weakened before the shoulders and upper arms. This can also affect an individual’s appearance through slanted shoulders, a crooked smile, flattened facial features, etc (“Muscular Dystrophy: Hope in Research”). 

Myotonic dystrophy, the most common form of muscular dystrophy in adults, causes muscle weakness in the face, feet, and hands for males and females. In addition to progressive weakness, people with myotonic dystrophy also experience an inability to relax muscles after a contraction. Symptoms can appear from birth to adulthood (“Muscular Dystrophy: Hope in Research”). 

Oculopharyngeal muscular dystrophy affects those in their forties or fifties. The first symptom is drooping eyelids and weakness around the muscles in the face and throat. Additionally, the tongue may also be affected. These symptoms result in issues with vision (such as double vision), difficulty swallowing, and changes in an individual’s voice (“Muscular Dystrophy: Hope in Research”). 

Distal muscular dystrophy is characterized by muscle weakness in the muscles of the forearms, hands, lower legs, and feet (distal muscles). While this group of dystrophies is less severe and progresses slowly, it results in difficulties in extending fingers and, similarly to other muscular dystrophies, walking (“Muscular Dystrophy: Hope in Research”).

Lastly, congenital muscular dystrophy is defined by muscle weakness at birth. Failure to meet motor function and muscle control landmarks are usually the first signs of this muscular dystrophy. Those with congenital muscular dystrophy have trouble sitting or standing without support and may never learn to walk (“Muscular Dystrophy: Hope in Research”).

Michelle Li, Youth Medical Journal 2021

References

Bosworth, Michelle Q., MS, and Rebecca J. Frey, PhD. “Duchenne and Becker Muscular Dystrophy.” The Gale Encyclopedia of Genetic Disorders, edited by Tracie Moy and Laura Avery, 4th ed., vol. 1, Gale, 2016, pp. 579-85. Gale Health and Wellness, link.gale.com/apps/doc/CX3630400165/HWRC?u=mlin_m_newtnsh&sid=HWRC&xid=14e7d476. Accessed 14 Feb. 2021.

“Muscular Dystrophy: Hope Through Research.” National Institute of Neurological Disorders and Stroke, ninds.nih.gov/Disorders/Patient-Caregiver-Education/Hope-Through-Research/Muscular-Dystrophy-Hope-Through-Research. Accessed 14 Feb. 2021.

Quercia, Nada, and Karl Finley. “Muscular Dystrophy.” The Gale Encyclopedia of Medicine, edited by Jacqueline L. Longe, 6th ed., vol. 6, Gale, 2020, pp. 3510-18. Gale in Context: Science, link.gale.com/apps/doc/CX7986601264/SCIC?u=mlin_m_newtnsh&sid=SCIC&xid=5502bdc3. Accessed 14 Feb. 2021.

By Michelle Li

Michelle Li is a high school junior in Massachusetts. She hopes to pursue medicine in the future and is especially interested in pediatrics.

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