This educational activity is credited for 4 contact hours at completion of the activity.
This course is designed to offer healthcare professionals a concise overview of muscular dystrophy, outlining its various forms, diagnostic approaches, and available interventions aimed at managing the condition and improving patient quality of life.
Muscular dystrophy refers to a group of inherited disorders characterized by progressive and widespread muscle degeneration caused by a deficiency or absence of glycoproteins in the muscle cell membrane. Each type of muscular dystrophy presents with distinct inheritance patterns, ages of onset, clinical features, and rates of muscle deterioration. This course provides an overview of muscular dystrophy, the various types, diagnostic methods, and management strategies to support individuals affected by the condition.
Upon completion of this course, the learner will be able to:
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| Angiotensin-Converting Enzyme (Ace) Inhibitors | Medicines that help relax the veins and arteries to lower blood pressure. |
| Apoptosis | The death of cells which occurs as a normal and controlled part of an organism’s growth or development. |
| Atrophy | The decrease in size or wasting away of a body part or tissue, or the process of such a decrease. |
| Cardiomyopathy | An acquired or inherited disease of the heart muscle which makes it difficult for the heart to pump blood to other parts of the body. |
| Contractures | The result of stiffness or constriction in the connective tissues of the body. |
| CTG Trinucleotide | The DNA mutation responsible for causing any type of disorder categorized as trinucleotide repeat disorder. |
| Deoxyribonucleic Acid (DNA) | A polymer composed of two polynucleotide chains that coil around each other to form a double helix. |
| Dystrophia Myotonica Protein Kinase (DMPK) | An enzyme that in humans is encoded by the DMPK gene. |
| Dystrophin Gene | The largest known human gene. |
| Dystrophin-Glycoprotein Complex (DGC) Proteins | Situated at the sarcolemma, dynamically remodels during cardiac disease. |
| Endomysia | Specific proteins produced by the immune system in response to a particular threat. |
| Glycoproteins | Proteins which contain oligosaccharide chains covalently attached to amino acid sidechains. |
| Heterozygotes | An organism who has different genes for a specific trait from one parent and another. |
| Hypertrophy | The enlargement of an organ or tissue from the increase in size of its cells. |
| Kyphoscoliosis | Abnormal curvature of the spine in both the coronal and sagittal planes. |
| Lordosis | The excessive inward curvature of the spine. |
| mRNA | A type of single-stranded RNA involved in protein synthesis. |
| Multiplex Ligation-Dependent Probe Amplification (MPLA) | A variation of the multiplex polymerase chain reaction that permits amplification of multiple targets with only a single primer pair. |
| Muscular Dystrophy | Refers to a group of more than 30 genetic (inherited) conditions that affect the functioning of muscles. |
| Myoglobinuria | A condition where urine turns dark red or brown due to excess myoglobin, a protein that carries oxygen in muscles. |
| Myotonia | The impairment of relaxation of skeletal muscles after voluntary contraction or electrical stimulation. |
| North Star Ambulatory Assessment | A 17-item rating scale that is used to measure functional motor abilities in ambulant children with Duchenne muscular dystrophy (DMD). |
| Nuclear Protein Emerin | A protein that in humans is encoded by the EMD gene, also known as the STA gene. |
| Polymerase Chain Reactions (PCR) | Amplifies a specific region of a DNA strand (the DNA target). |
| Proximal Muscles | Muscles closest to the center of the body, such as the muscles in the shoulders, upper arms, hips, and thighs. |
| Ptosis | A condition in which there is drooping of upper eyelid either in one eye or both the eyes. |
| Rand Corporation | A research organization that provides fact-based, actionable solutions to improve policy and decision making. |
| Scoliosis | A condition characterized by sideways curvature of the spine or back bone, often noted during growth spurt just before a child attains puberty. |
| Somatic Cells | The building blocks of the body, except for the reproductive cells that create new life. |
| Udd Distal Myopathy | A condition that affects the muscles at the front of the lower leg. |
| Welander Distal Myopathy | An autosomal dominant disorder characterized by adult onset of distal muscle weakness predominantly affecting the distal long extensors of the hands, with slow progression to involve all small hand muscles and the lower legs. |
Muscular dystrophy refers to a group of inherited disorders that result in progressive degeneration of skeletal muscle due to the absence or deficiency of glycoproteins in the muscle cell membrane.¹ This degeneration typically begins in a specific group of muscles and gradually expands, leading to widespread muscle weakness over time.²
Muscular dystrophy (MD) is a non-infectious condition with numerous variants, each defined by its genetic origin, age of onset, and rate of progression.¹ Mutations in particular genes produce different forms of the disorder.¹ For example, the various types of MD impact different muscle groups, with symptoms emerging at various life stages and progressing with differing levels of severity.³ In more advanced stages, some types of MD may compromise the heart or respiratory muscles, posing serious health risks.²
Though considered rare, muscular dystrophies are serious conditions with limited prevalence data available.³ This course provides a comprehensive overview of muscular dystrophy, including its classifications, diagnostic methods, and strategies for effective management.
The manifestations of muscular dystrophy vary based on the age of onset, rate of symptom progression, and which muscle groups are primarily affected.⁴ Depending on the underlying genetic cause, some types extend beyond skeletal muscle involvement, with several forms exhibiting significant cardiac complications.⁴
Common types of muscular dystrophy include:
Duchenne Muscular Dystrophy (DMD)
DMD results from a mutation in the dystrophin gene located at Xp21 on the short arm of the X chromosome.¹ It is one of the most prevalent and severe forms, typically affecting boys in early childhood.² Symptoms usually emerge before age five and first involve the upper legs and arms.³
As the condition progresses, patients develop profound weakness in the limbs, trunk, and diaphragm, eventually leading to kyphoscoliosis and respiratory failure.⁴ Life expectancy often does not extend beyond the third decade due to respiratory complications.⁴
In females, DMD may occur due to X-inactivation, resulting in mosaic expression of the gene, which often provides partial protection against symptoms.¹
Becker Muscular Dystrophy (BMD)
BMD is linked to mutations in the dystrophin gene, the largest known human gene comprising 79 exons.¹ Although it shares genetic similarities with DMD, BMD manifests later in childhood and is less severe.² Most individuals retain normal life expectancy.
Myotonic Muscular Dystrophy
This form arises from impaired expression of the DMPK gene due to expanded CTG trinucleotide repeats in its 3′ untranslated region.¹ It follows an autosomal dominant inheritance pattern and affects approximately 8 per 100,000 individuals.³
Symptoms, including muscle weakness, typically begin in the face, neck, arms, hands, hips, and lower legs.³ While life expectancy is not always impacted, severe cases may shorten lifespan.²
Limb-Girdle Muscular Dystrophy (LGMD)
LGMD refers to a collection of disorders typically presenting in late childhood or early adulthood.¹,² It affects males and females equally and occurs in about 2 per 100,000 people.³
Variants result from mutations or deletions in several genes, including:
Muscle groups impacted include the upper arms and legs, heart, spine, hips, calves, and trunk.³ Disease progression varies significantly by subtype.²
Facioscapulohumeral Muscular Dystrophy (FSHD)
FSHD is caused by autosomal dominant deletions of 3.3 kb repeats on chromosome 4, specifically in the D4Z4 region in FSHD1, or in SMCHD1 for FSHD2.¹
It usually begins in childhood or adulthood and progresses slowly.² Initial muscle weakness typically affects the face, shoulders, and upper arms, with potential later involvement of the eyes, ears, and lower legs.³ FSHD is rarely life-threatening.
Emery-Dreifuss Muscular Dystrophy (EDMD)
EDMD is linked to X-linked recessive mutations in the emerin protein gene at Xq27-28, or autosomal mutations in lamin A/C on chromosome 1.¹
It primarily affects males and presents in childhood or early adulthood.² Life expectancy generally extends into midlife.² Inheritance patterns include X-linked, autosomal dominant, and autosomal recessive.
Oculopharyngeal Muscular Dystrophy (OPMD)
OPMD arises from an autosomal dominant GCG trinucleotide repeat expansion that impairs mRNA transport.¹ Symptoms typically emerge between ages 50–60, affecting the extraocular and pharyngeal muscles.¹,² Life expectancy is usually not affected.²
Congenital Muscular Dystrophy (CMD)
CMD is linked to mutations in genes encoding sarcolemmal proteins such as merosin, laminin-α2, collagen VI, integrin-α7, and glycosyltransferases.¹ It occurs in about 1 per 100,000 people, regardless of sex.³
CMD affects the neck, upper limbs, lungs, brain, heart, and spine.³
Distal Muscular Dystrophy
This class targets distal muscle groups—those in the hands, forearms, lower legs, and feet.⁶ It has a slow progression and does not affect cognitive function.⁶
The disorder can emerge in childhood or adulthood and is caused by mutations in at least eight genes, inherited via autosomal dominant or recessive patterns.⁶
Summary
There are more than 30 known types of muscular dystrophy.⁷ They differ based on genetic mutation, the severity of muscle degeneration, and the specific muscle groups involved.⁷
Duchenne Muscular Dystrophy (DMD)
DMD typically manifests in early childhood.⁸ Affected children show progressive weakness and muscle wasting in proximal muscles—those closest to the trunk—particularly in the upper legs, pelvic region, upper arms, and shoulders.⁸ Common clinical features include:⁷
As the disease advances, weakness extends to the lower legs, forearms, neck, and trunk.⁸ Involvement of respiratory muscles often leads to pneumonia, impaired coughing, and eventual respiratory failure.⁸
Becker Muscular Dystrophy (BMD)
BMD and DMD share similar inheritance patterns and muscle involvement.⁷ However, BMD is less severe and progresses more slowly.⁷ Muscle weakness typically begins around age 8, though in milder cases with limited cardiac involvement, onset may be delayed until age 15.⁹ Heart failure is the leading cause of death.⁹ Clinical signs resemble those of DMD but are milder and more variable.⁷
Myotonic Dystrophy
Myotonic dystrophy differs from other types in that it includes both muscle weakness and myotonia—difficulty relaxing muscles after contraction—along with multiple systemic symptoms.⁷ The initial weakness often affects facial muscles, the neck, hands, forearms, and feet.⁷
Approximately half of affected individuals display visible signs by age 20, while most develop symptoms by age 50.⁷ Presentation is highly variable, ranging from mild manifestations to severe muscle wasting and disability.⁷ Some may only develop cataracts as their sole symptom.⁷
Limb-Girdle Muscular Dystrophy (LGMD)
LGMD displays wide variability in age of onset, severity, and symptom progression, even among family members.¹⁰ Major signs include:
Additional features may include:¹⁰
Facioscapulohumeral Muscular Dystrophy (FSHD)
FSHD progresses slowly, and most patients retain the ability to walk and live a normal lifespan.⁷ Symptoms may appear anytime from infancy to the fifth decade.⁷ Characteristic signs include:
Emery-Dreifuss Muscular Dystrophy (EDMD)
EDMD presentation varies widely in onset, severity, and progression.¹¹ It is defined by a triad of:
Muscle weakness often advances during the first three decades and may become more pronounced thereafter.¹¹
Oculopharyngeal Muscular Dystrophy (OPMD)
OPMD is characterized by gradual weakening of the eye and throat muscles, and occasionally the pelvic and shoulder regions.¹² Common early symptoms include:
Congenital Muscular Dystrophy (CMD)
Symptoms generally present at birth or within the first few months.⁷
Typical signs include:
Some children may show improvement in motor function during early years, with slow or minimal disease progression.⁷
Distal Muscular Dystrophy
Distal muscular dystrophies include several subtypes, each with unique onset, progression, and muscle involvement.¹³
Duchenne Muscular Dystrophy (DMD)
Duchenne muscular dystrophy is a rare but one of the most common inherited muscle disorders, affecting roughly 1 in every 3,500 male births globally.⁸
Pathophysiology
DMD is characterized by the absence of both dystrophin and the dystrophin-glycoprotein complex (DGC), leading to increased fragility and permeability of muscle cell membranes, disturbances in calcium balance, and oxidative damage.¹⁴
Dystrophin, a large cytoskeletal protein, is essential for linking the cytoskeleton of muscle cells to the cell membrane and extracellular matrix. It is found in both muscle and non-muscle tissues and plays a critical structural role in muscle integrity.¹⁴
Without dystrophin and its associated proteins, muscle fibers become prone to necrosis. Over time, the regenerative capacity of muscles diminishes, and muscle tissue is replaced by connective and fat tissue.¹⁴
Diagnosis
Diagnosis of DMD is based on clinical examination, patient history, and specialized testing, including molecular genetic evaluations.⁸ If genetic analysis is inconclusive, a muscle biopsy can confirm the diagnosis through distinctive histological changes.⁸
Laboratory workup may include creatine kinase levels, genetic testing, and electrocardiography to assess for cardiomyopathy.¹⁴
Creatine Kinase (CK) Testing
CK levels in the blood become significantly elevated when muscles are damaged.⁸ In DMD, CK levels can be 10 to 20 times above the normal limit and often peak by age two, before symptoms appear.¹⁴ Even asymptomatic carriers may show elevated CK.¹⁴ As muscle tissue is replaced by fat and fibrous tissue with disease progression, CK levels typically decline. Other enzymes such as aldolase and AST may also be elevated.¹⁴
Muscle Biopsy
Histological findings include proliferation of endomysial connective tissue, degeneration and regeneration of muscle fibers, fiber necrosis, mononuclear infiltrates, and fat infiltration.¹⁴ Diagnostic methods include immunostaining, immunofluorescence, and Western blot.⁸ Commonly biopsied muscles include the quadriceps femoris and gastrocnemius.¹⁴
Genetic Testing
Genetic testing involves analyzing DNA for mutations such as deletions, duplications, or point mutations.⁸ DMD patients often show a near-complete absence of dystrophin gene expression.¹⁴ Immunoblotting helps assess disease severity; less than 5% of normal dystrophin is typically found in affected individuals.¹⁴
Techniques such as PCR and MPLA are used to detect mutations.¹⁴ Dystrophin immunocytochemistry can identify cases missed by PCR.¹⁴
Electrocardiogram (ECG)
ECG changes in DMD may include tall R waves in leads V1-V6 with an elevated R/S ratio, and deep Q waves in leads I, aVL, and V5-V6.¹⁴ Telemetry may detect supraventricular arrhythmias and conduction disturbances, with intra-atrial defects being more frequent than AV block or infranodal abnormalities.¹⁴
Prognosis
DMD carries a poor prognosis.¹⁴ Most patients become wheelchair-bound by age 12. Death typically occurs in adolescence or early adulthood due to respiratory or cardiac failure, with other potential causes including pneumonia, aspiration, or airway obstruction.¹⁴
Treatment and Management of Duchenne Muscular Dystrophy (DMD)
There is currently no medical cure for DMD, and the condition carries a poor prognosis.¹⁴ Treatment focuses on managing symptoms and improving quality of life through a multidisciplinary approach tailored to individual needs.⁸ Common interventions include:⁸
Glucocorticoid Therapy
Glucocorticoids help slow muscle fiber degeneration by reducing apoptosis in myotubes and limiting inflammation.¹⁴ This therapy has been shown to:
FDA-Approved Medications for DMD:
Orthopedic Interventions
Orthopedic strategies are designed to preserve mobility and posture.¹⁴
Pulmonary Care
Pulmonary assessments should begin before the patient transitions to exclusive wheelchair use and be repeated biannually after age 12 or when vital capacity drops below 80%.¹⁴
Exercise and Nutrition
Cardiac Management
To address cardiomyopathy:
Advancements in the Management of Duchenne Muscular Dystrophy (DMD)
Management strategies for DMD have advanced significantly in recent decades.¹⁵ Updated standards of care reflect thorough systematic reviews and consensus from international experts. These guidelines now encompass not only muscular issues but also multi-organ involvement and psychosocial support.¹⁵
International Standards of Care
Originally published in 2010 and later expanded, the international standards of care for DMD provide a comprehensive framework across all disease stages: diagnosis, early ambulatory, late ambulatory, early non-ambulatory, and late non-ambulatory.¹⁵
This initiative, supported by the US Centers for Disease Control and various advocacy organizations, gathered expert panels through RAND Corporation’s structured process. These standards serve as a universal baseline for diagnosis, monitoring, and treatment.¹⁵
Neuromuscular Management
A neuromuscular specialist plays a central role in guiding patients and families, defining care goals, and assisting with care transitions from pediatric to adult services.¹⁵ Key neuromuscular management practices include:
Rehabilitation Management
Ongoing, individualized rehabilitation involves multidisciplinary evaluations and standardized assessments such as the North Star Ambulatory Assessment and timed function tests.¹⁵
Respiratory Management
Orthopedic Management
Early and Late Ambulatory Stages:
Early Non-Ambulatory Stage:
Late Non-Ambulatory Stage:
Cardiac Management
Ambulatory Stages:
Post-Ambulation Loss:
Conclusion
Adherence to these structured standards of care is crucial to enhancing or preserving function and quality of life in DMD patients.¹⁵ Evidence shows that timely respiratory support, scoliosis management, and targeted cardiac therapies have significantly extended life expectancy. However, these advances can also result in prolonged survival with severe physical limitations. Ultimately, patients should be supported in making personal decisions regarding the continuation or withdrawal of treatment.¹⁵
Nursing Considerations for Patients with Duchenne Muscular Dystrophy (DMD)
Fatigue
Nursing strategies include:¹⁶
Impaired Physical Mobility
Nursing strategies include:¹⁶
Risk for Falls
Nursing strategies include:¹⁶
Risk for Injury
Nursing strategies include:¹⁶
Risk for Ineffective Breathing Patterns
Nursing strategies include:¹⁶
Over the past two decades, there has been a substantial increase in preclinical studies, animal-based research, and clinical trials related to Duchenne muscular dystrophy (DMD).¹⁵ Advancements in understanding the genetic and pathological mechanisms underlying the condition have led to exploration of several therapeutic strategies, including:¹⁵
As a result of these promising advances, the previously pessimistic outlook for managing DMD and similar genetic neuromuscular disorders is no longer warranted.¹⁵ Moreover, notable progress has been made in supportive and rehabilitative interventions.¹⁵
Despite these advancements, a definitive cure or method to halt disease progression remains elusive. Treatment continues to be focused on managing symptoms.¹⁵
Effective DMD management requires a coordinated interprofessional team that includes specially trained nurses and therapists.¹⁴ The overarching priority is to help patients maintain the highest possible quality of life.
To access Muscular Dystrophy: A Quick Overview, purchase this course or a Full Access Pass.
If you already have an account, please sign in here.
To access Muscular Dystrophy: A Quick Overview, purchase this course or a Full Access Pass.
If you already have an account, please sign in here.
