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Duchenne muscular dystrophy
This condition predominantly affects males and leads to difficulties with movement, eventually impacting heart and breathing functions. It results from genetic changes that prevent the body from producing functional dystrophin, a crucial muscle protein.
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Overview
Duchenne muscular dystrophy (DMD) is a severe, progressive genetic condition that primarily affects muscles throughout the body. It leads to muscle weakness and wasting, which means that muscles gradually become weaker and lose tissue over time. While DMD primarily affects skeletal muscles, which are responsible for movement, it can also impact the heart muscle (cardiomyopathy) and muscles involved in breathing [PMID:33675087]. The condition is much more common in males than in females.
Symptoms typically appear in early childhood, often between the ages of 2 and 3 years. Children with DMD may experience difficulties with walking, running, and climbing stairs. The muscle weakness progresses, leading to loss of mobility and, in later stages, affecting heart and respiratory function. The severity and rate of progression can vary, but DMD generally follows a predictable course.
Living with DMD involves ongoing medical care and support. The NHS provides a pathway for diagnosis and management, focusing on multidisciplinary care to address the various aspects of the condition and support individuals and their families.
Symptoms & clinical features
The initial symptoms of Duchenne muscular dystrophy often become noticeable in early childhood. Affected boys may have difficulty achieving developmental milestones such as walking independently. When they do learn to walk, they might have a waddling gait and fall frequently [PMID:33675087].
Other early signs can include trouble standing up from a sitting or lying position, often using their hands to 'climb up' their legs (a manoeuvre known as Gowers' sign). Calf muscles might appear unusually large, which is due to muscle tissue being replaced by fat and connective tissue, a process called pseudohypertrophy. As the condition progresses, muscle weakness affects the arms, neck, and other areas, leading to further loss of mobility.
In later stages, muscle weakness can affect the diaphragm and other muscles needed for breathing, potentially leading to respiratory problems. The heart muscle can also be affected, leading to cardiomyopathy, which requires regular monitoring and management. Some individuals with DMD may also experience learning or behavioural difficulties, though these vary in severity.
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Affected organs
Duchenne muscular dystrophy primarily affects muscles throughout the body. The most visibly impacted are the skeletal muscles, which are the voluntary muscles responsible for movement. This leads to progressive weakness and wasting in the limbs and trunk.
Beyond skeletal muscles, the heart muscle is commonly affected, leading to a condition called cardiomyopathy. This can weaken the heart's ability to pump blood effectively, and regular cardiac monitoring is an essential part of managing DMD. The respiratory muscles, including the diaphragm, are also affected, which can lead to breathing difficulties over time. In some cases, the condition may also have an impact on brain function, potentially leading to cognitive and behavioural differences.
Risks & severity
Duchenne muscular dystrophy is considered a severe condition with a progressive course. The exact prevalence is estimated to be between 1 in 3,500 and 1 in 5,000 live male births [PMID:33675087]. Symptoms typically emerge in early childhood, often between ages 2 and 3. Most affected boys require a wheelchair for mobility by their early teens. The progression of muscle weakness is relentless, eventually affecting the heart and respiratory system.
While the condition is severe, significant advancements in medical care mean that individuals with DMD are living longer and with improved quality of life. Management strategies focus on slowing progression, treating symptoms, and preventing complications. There is a spectrum of severity, even within DMD, though it is generally understood as a severe condition leading to significant disability.
Genetic causes
Duchenne muscular dystrophy is caused by pathogenic variants in the DMD gene, which stands for dystrophin. This gene is one of the largest known human genes and contains the instructions for making a protein called dystrophin. Dystrophin is crucial for the normal function and integrity of muscle cells [PMID:33675087].
Within muscle cells, dystrophin acts like a shock absorber or a structural anchor. It connects the internal framework (cytoskeleton) of the muscle cell to the outer cell membrane and the surrounding extracellular matrix. This connection is vital for maintaining the stability of muscle fibres during contraction and relaxation. Without functional dystrophin, muscle cells become fragile and are easily damaged during normal activity [PMID:25642647].
The ongoing damage to muscle fibres leads to a cycle of degeneration and regeneration. Over time, the muscle's ability to regenerate is exhausted, and muscle tissue is replaced by fibrous tissue and fat, leading to the characteristic muscle weakness and wasting seen in DMD. Pathogenic variants in DMD can include deletions, duplications, or point changes that prevent the production of any functional dystrophin.
- DMD dystrophinThe DMD gene provides instructions for producing dystrophin, a protein essential for maintaining the structural integrity of muscle fibres, particularly in skeletal and heart muscles.
Inheritance pattern
Duchenne muscular dystrophy has an X-linked recessive (XLR) inheritance pattern. This means the DMD gene is located on the X chromosome, one of the two sex chromosomes. Females have two X chromosomes, while males have one X and one Y chromosome.
Because males only have one X chromosome, if they inherit an X chromosome with a pathogenic variant in the DMD gene, they will develop the condition. Females, having two X chromosomes, are typically 'carriers' if they have one affected X chromosome and one unaffected X chromosome. Carriers generally do not show symptoms of DMD, or they may experience milder symptoms like muscle weakness or heart problems (carrier cardiomyopathy) due to a phenomenon called skewed X-inactivation. A carrier mother has a 50% chance of passing the pathogenic variant to each child. Her sons have a 50% chance of developing DMD, and her daughters have a 50% chance of being carriers. Affected males do not pass the condition to their sons, but all their daughters will be carriers.
X-linked recessive: sons of a carrier mother have a 50% chance of being affected. Daughters have a 50% chance of being carriers.
Diagnosis & testing
The diagnosis of Duchenne muscular dystrophy often begins when parents or healthcare professionals notice developmental delays or muscle weakness in a young boy. Initial investigations may include a blood test to measure the level of creatine kinase (CK), an enzyme that is typically very high in individuals with DMD due to muscle damage.
Confirmation of DMD requires genetic testing, which looks for pathogenic variants in the DMD gene. This testing is crucial for a definitive diagnosis and for understanding the specific genetic change, which can be important for management and potential treatment options. Genetic testing for DMD is available through the NHS Genomic Medicine Service (GMS), often following a referral from a paediatrician or neurologist to a clinical genetics service. Relevant R-codes for genetic testing would typically include R103 (Inherited muscular dystrophy). A genetic counsellor can explain the testing process, results, and implications for the individual and family.
Management & lifestyle
While there is currently no cure for Duchenne muscular dystrophy, management focuses on slowing disease progression, treating symptoms, and enhancing quality of life. This involves a multidisciplinary team approach, often including neurologists, cardiologists, respiratory specialists, physiotherapists, occupational therapists, and genetic counsellors.
Corticosteroids, such as prednisolone, are often prescribed to help preserve muscle strength and function, although they also have potential side effects that need careful management. Physical therapy and occupational therapy are vital to maintain mobility, prevent contractures, and adapt to changing physical needs. Regular cardiac monitoring and early intervention for cardiomyopathy are crucial. Respiratory support, including non-invasive ventilation, may become necessary as breathing muscles weaken.
Genetic counsellors play a key role in providing information about the condition, inheritance patterns, and reproductive options for families. Emerging therapies, including gene-specific treatments for certain types of DMD variants, are also becoming available through NHS pathways, offering new avenues for managing the condition. Individual medical management plans are tailored to the specific needs of each patient.
UK care pathway
In the UK, the care pathway for individuals with Duchenne muscular dystrophy is integrated within the NHS Genomic Medicine Service. If DMD is suspected, a referral to a paediatrician or neurologist is typically the first step. They will then assess the need for genetic testing, which falls under specific NHS R-codes, such as R103 for inherited muscular dystrophies.
Once a diagnosis is confirmed, individuals and their families are usually referred to a clinical genetics service. This service provides expert advice, helps interpret genetic test results, and offers genetic counselling. Genetic counsellors are essential for explaining the inheritance pattern, discussing the implications for family members, and providing support. Management involves a multidisciplinary team, with care coordinated through specialist centres.
Frequently asked questions
How common is Duchenne muscular dystrophy?
Duchenne muscular dystrophy is a rare condition, primarily affecting males. It is estimated to occur in approximately 1 in 3,500 to 1 in 5,000 live male births.
Can females be affected by Duchenne muscular dystrophy?
While Duchenne muscular dystrophy primarily affects males, females can be carriers of the condition. In rare cases, female carriers may experience milder symptoms such as muscle weakness or heart problems, but typically they do not develop the full condition.
When do symptoms usually start?
Symptoms of Duchenne muscular dystrophy typically become noticeable in early childhood, often between the ages of 2 and 3 years. Initial signs may include difficulties with walking, running, or climbing stairs.
Is there a cure for Duchenne muscular dystrophy?
Currently, there is no cure for Duchenne muscular dystrophy. However, ongoing medical care and management, including therapies and supportive treatments, aim to slow the progression of the disease and improve quality of life. New genetic therapies are also emerging.
How is Duchenne muscular dystrophy diagnosed?
Diagnosis typically involves a blood test to check for high levels of creatine kinase, followed by genetic testing to identify specific pathogenic variants in the DMD gene. This genetic testing is usually confirmed through NHS Genomic Medicine Services.
References
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- Owens AT, Jessup M. Cardioprotection in Duchenne muscular dystrophy. European heart journal. 2021. PMID: 33748844
- Lee-Gannon T, Jiang X, Tassin TC. Biomarkers in Duchenne Muscular Dystrophy. Current heart failure reports. 2022. PMID: 35386072
- Desguerre I. Duchenne muscular dystrophy in 2025. Archives de pediatrie : organe officiel de la Societe francaise de pediatrie. 2025. PMID: 41391903