What Is Muscular Dystrophy

Overview

Muscular Dystrophy (MD) is a collective name for a group of rare genetic neuromuscular diseases that progressively weaken and irreparably damage the muscles. While the National Institutes of Heath (NIH) has identified approximately 30 variations of MD , there are nine common types of the condition which will be explored in this article.¹

Each type of muscular dystrophy affects different muscle groups, and therefore there is variation in the conditions’ presentation and severity. While a cure for the disease is yet to be discovered, numerous treatment options aid in managing the devastating symptoms of MD. These will also be outlined in this article.

This article will enhance your understanding of Muscle dystrophy by explaining the disease’s cause, the associated signs and symptoms, treatment strategies and answering frequently asked questions about the condition.

Causes of muscular dystrophy

Being a genetic disorder, muscular dystrophy is caused by a mutation in any gene involved in proper muscle functioning. 

Muscle functioning is an integral aspect of life regulated by numerous proteins and, therefore, genes.² Consequently, many possible mutations could cause muscular dystrophy. This inheritance pattern is why there are multiple forms of this disease.

An additional result of this factor is the inheritance mode of these genetic mutations. Typically, genetic mutations are inherited from either one or both parents. So while one can inherit an MD causative mutation in both these ways, this mutation can arise spontaneously. 

This trait makes this rare genetic disease even more sporadic in presentation.

Signs and symptoms of muscular dystrophy

The best indication of the onset of muscular dystrophy is progressive muscular weakness. Given the established variation in muscular dystrophy, this weakness will be observed in different muscle groups and arise at different ages. Therefore, after an overview of the general symptoms of MD, this section will explore specific manifestations of the leading forms of muscular dystrophy.

General symptoms of Muscular dystrophy:

• Muscle weakness
• Muscle cramping
• Difficulty moving
• Loose or stiff joints
• An atypical waddling walk
• Learning disabilities
• Scoliosis
• Breathing difficulty
• Swallowing difficulty
• Cardiovascular complications

Duchenne muscular dystrophy (DMD)

DMD is the most prevalent form of muscular dystrophy. This disease variation is observed in early childhood, in toddlers as young as two years. It is classified as dystrophinopathy because it is caused by a mutation in an X chromosome gene associated with the expression of dystrophin.³ Dystrophin is a protein that plays an integral role in muscle integrity. This protein is a primary component of skeletal and cardiac muscles; therefore, dystrophinopathies like DMD have severe impacts.⁴ As this is an X-linked disorder, Duchenne muscular dystrophy is more typical in males than females.³

This form of MD is characterised by progressive degeneration of the proximal muscles, which are those localised to the centre of the body (i.e. the muscles of the upper arms, shoulders, pelvis and legs). Therefore, common symptoms of Duchenne-type muscular dystrophy include muscle weakness, impaired mobility and a distinct waddling gait. As the child ages, they will experience pulmonary impairments due to weakened cardiac and respiratory muscles.^{3, 5} 

Without intervention, children can live with DMD into their teenage years. However, medical advancements, which will be explored later on in this article, can significantly increase their lifespans.

Becker muscular dystrophy

BMD is another dystrophinopathy similar to but less severe than DMD. BMD symptoms appear later than in DMD and are milder in comparison.⁶ This is because the genetic mutation causing BMD reduces dystrophin functionality instead of completely stopping it (which is the case with DMD). ^{6, 7} The signs of this form of muscular dystrophy are the same as with DMD, with the main difference being the age of symptom onset, as BMD can arise anywhere from 5 to 60 years.^{6, 8} People with this type of muscular dystrophy have a longer life expectancy into their mid-adulthood. Still, there is research into improving their quality of life and extending their lifespans.

Myotonic muscular dystrophy

This form of muscular dystrophy is caused by a dominantly inherited mutation in either the DMPK gene or the CNBP gene. The proteins produced by these genes are integral in heart and skeletal muscles and brain cells' functioning. Therefore, myotonic muscular dystrophy results in limited mobility and impaired electrical conduction necessary for cardiac contraction, breathing, swallowing, bowel movement, and optic and neurological functioning. Distinct symptoms of this variant include a diminished appearance of the muscles in the face, jaw, neck and hands, myotonia (muscle stiffness), slurred speech, dysphagia (difficulty swallowing), cataracts, bowel problems, cardiac arrhythmia and personality issues. ⁹

Congenital muscular dystrophy (CMD)

This rare form of muscular dystrophy has the earliest onset, with symptoms observed at birth.¹⁰ Congenital MD is caused by a mutation in the genes-producing proteins of the extracellular matrix, which is an integral element of muscle cells.¹¹ This mutation limits muscle functioning resulting in muscle and joint weakness, scoliosis, respiration challenges and intellectual disabilities.¹⁰ 

Limb girdle muscular dystrophy (LGMD)

Limb-girdle muscular dystrophies are a diverse category of this disorder, given that there are different LGMD subtypes. The main muscle groups affected are those in the pelvis and the shoulders, so the main symptom of this form of MD is the distinct waddling gait.¹² Age of onset varies with the subtypes; however, LGMD is typical in adolescence.

Facioscapulohumeral muscular dystrophy (FSHD)

Facioscapulohumeral muscular dystrophy is the progressive degeneration of muscles in the face, shoulders and upper arms. The symptoms typically become apparent in the teenage years, including raised arms and a distorted wing-like appearance of the shoulder blades. FSHD is caused by a mutation affecting the expression of the double homeobox protein.^{13, 14}

Distal muscular dystrophy 

This rare muscle dystrophy affects the distal muscles of the lower arms and legs. Typical onset is between 40 to 60 years, and because of the affected muscle groups, symptoms include difficulty walking and gripping things.¹⁵ Like with Limb-girdle MD, distal muscular dystrophy has a range of subtypes with further unique presentations.

Oculopharyngeal muscular dystrophy

This is another rare form of MD that affects the eyes' ocular muscles and the throat's pharyngeal muscles. Symptoms include dysphagia, difficulty moving the eyes, droopy eyelids and weak limbs.¹⁶

Emery dreifuss muscular dystrophy

Emery-Dreifuss muscular dystrophy is an X-linked genetic disorder that results in muscle weakness and contractures.¹⁷ Consequently, people with this form of MD find it challenging to raise their arms and lift objects. Walking is also tricky for them as the disease progresses. Furthermore, there is a cardiovascular effect of Emery-Dreifuss MD in some patients, which results in an unusual heart rate.¹⁸

Management and treatment of muscular dystrophy

Typical of many genetic conditions, there is no cure for muscular dystrophy. However, different approaches are developed to address the symptoms and ongoing research into effective treatment methods, specifically gene-based therapies like exon skipping.

• Physical therapy: if started early, physical therapy can significantly improve muscle strength and flexibility, making the approach effective in managing MD
• Mobility assistance: muscular dystrophy restricts mobility, so doctors recommend low-impact exercise, occupational therapy and using mobility devices like wheelchairs or crutches to simplify movement
• Speech therapy: Speech therapy is especially beneficial for managing Facioscapulohumeral muscular dystrophy. This approach will equip patients with techniques and equipment to improve their speaking ability
• Respiratory therapy: Respiratory therapy is recommended as a preventative approach against the pulmonary impact of Muscular dystrophy. Low-impact exercise is initially recommended; however, some people require ventilators to support breathing when the disease progresses
• Corrective surgery: This approach effectively addresses symptoms like scoliosis, cataracts, joint tightness or eyelid drooping
• Simplifying swallowing: Dysphagia is a common symptom of different forms of MD, so approaches that address swallowing concerns are effective management strategies. Swallowing can be facilitated through specific exercises changing food consistency, and surgical intervention where necessary   
• Pharmaceutical interventions: A range of drugs can be used to manage the symptoms of muscular dystrophy. For instance, beta blockers or pacemakers effectively address heart problems, Glucocorticoids or creatine supplements improve respiratory function and muscle strength, and anticonvulsants treat muscle spasms¹⁹

FAQs

How is muscular dystrophy diagnosed?

Following a consultation with your GP, your doctor could recommend these approaches to diagnose muscular dystrophy: enzyme or genetic testing, muscle biopsies, heart or lung monitoring tests or electromyography.

How can I prevent muscular dystrophy?

As it is a genetic condition, if you are predisposed to getting muscular dystrophy, you, unfortunately, cannot prevent the disease. Living a healthy lifestyle can make the condition more manageable.

When should I see a doctor?

You should see a doctor if you experience progressive muscle weakness.

Summary

Overall, muscular dystrophy is a rare genetic disease that causes progressive muscle weakness thereby affecting mobility. The condition has variable forms affecting different proteins and muscle groups so the disease presentation consequently varies from person to person. Although there is no established cure for the disease, there is promising research in the field and a range of management strategies to address and manage muscular dystrophy symptoms.