Muscular dystrophy, Duchenne and Becker type

A genetic disorder characterized by progressive muscle degeneration and weakness

Duchenne and Becker Muscular Dystrophy
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Synonyms	N/A
Pronounce	N/A
Specialty	N/A
Symptoms	Muscle weakness, difficulty walking, scoliosis
Complications	N/A
Onset	Childhood (Duchenne), Adolescence or adulthood (Becker)
Duration	Lifelong
Types	N/A
Causes	Genetic mutations in the dystrophin gene
Risks	N/A
Diagnosis	Genetic testing, muscle biopsy
Differential diagnosis	N/A
Prevention	N/A
Treatment	Physical therapy, corticosteroids, cardiac care
Medication	N/A
Prognosis	Variable, depends on type and management
Frequency	Duchenne: 1 in 3,500 male births, Becker: 1 in 18,000 male births
Deaths	N/A

Muscular dystrophy, Duchenne and Becker type are two closely related genetic disorders characterized by progressive muscle degeneration and weakness. Both conditions are caused by mutations in the dystrophin gene, which is located on the X chromosome. This gene is responsible for producing dystrophin, a protein that helps stabilize and protect muscle fibers.

Pathophysiology

Duchenne and Becker muscular dystrophies are X-linked recessive disorders, meaning they primarily affect males, while females can be carriers. The difference between the two lies in the nature of the mutations in the dystrophin gene. In Duchenne muscular dystrophy (DMD), the mutations typically result in little to no functional dystrophin being produced, leading to more severe symptoms. In Becker muscular dystrophy (BMD), the mutations allow for some functional dystrophin, resulting in a milder phenotype.

Clinical Presentation

Duchenne Muscular Dystrophy

DMD is the more severe form and usually presents in early childhood. Symptoms often begin between ages 2 and 5 and include:

• Delayed motor milestones
• Difficulty running and jumping
• Frequent falls
• Waddling gait
• Enlarged calf muscles (pseudohypertrophy)

As the disease progresses, children with DMD may develop scoliosis, respiratory difficulties, and cardiomyopathy. Most individuals with DMD require a wheelchair by their early teens and have a shortened life expectancy, often living into their 20s or 30s.

Becker Muscular Dystrophy

BMD is milder and has a later onset, typically in adolescence or early adulthood. Symptoms are similar to DMD but progress more slowly. Individuals with BMD may remain ambulatory into their 30s or 40s and have a longer life expectancy, often into middle age.

Diagnosis

Diagnosis of Duchenne and Becker muscular dystrophies involves a combination of clinical evaluation, family history, and diagnostic tests. Key diagnostic tools include:

• Creatine kinase (CK) levels: Elevated CK levels indicate muscle damage.
• Genetic testing: Identifies mutations in the dystrophin gene.
• Muscle biopsy: May be used to assess dystrophin levels and muscle pathology.

Management

There is currently no cure for Duchenne or Becker muscular dystrophy, but various treatments can help manage symptoms and improve quality of life:

• Physical therapy: Helps maintain muscle strength and flexibility.
• Corticosteroids: Can slow muscle degeneration and improve strength.
• Cardiac care: Regular monitoring and treatment for cardiomyopathy.
• Respiratory support: Non-invasive ventilation may be needed as the disease progresses.

Research and Future Directions

Research is ongoing to find more effective treatments and potential cures for Duchenne and Becker muscular dystrophies. Approaches being explored include gene therapy, exon skipping, and stem cell therapy.

Also see

• Muscular dystrophy
• Dystrophin
• X-linked recessive inheritance
• Gene therapy