Becker muscular dystrophy
Becker muscular dystrophy is a milder, later-onset X-linked dystrophinopathy causing progressive proximal weakness and dilated cardiomyopathy from partially functional dystrophin. Diagnosis rests on elevated creatine kinase and confirmatory dystrophin genetic testing, and management centers on cardiac surveillance with ACE-inhibitor and beta-blocker therapy, physical therapy, and genetic counseling rather than the glucocorticoid regimen used in Duchenne muscular dystrophy.
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What this article covers
- Overview
Definition: Becker muscular dystrophy is an X-linked recessive dystrophinopathy caused by in-frame mutations in the dystrophin gene (DMD) that produce a partially functional, reduced-quantity or…
- Epidemiology
Incidence: Becker muscular dystrophy is less common than Duchenne muscular dystrophy, affecting roughly 1 in 18,000 to 30,000 male births.
- Risk factors
Male sex: X-linked recessive inheritance means male offspring of a carrier mother have a 50% chance of inheriting the mutated allele and being affected.
- Pathophysiology
Dystrophin's structural role: dystrophin anchors the intracellular cytoskeleton to the extracellular matrix through the dystrophin-glycoprotein complex at the muscle cell membrane, stabilizing the sarcolemma during repeated contraction.
- Clinical features
Proximal, symmetric weakness: progressive weakness of the hip and shoulder girdle muscles, more pronounced than distal weakness, with difficulty climbing stairs, rising from a squat, or raising the arms overhead.
- Differential diagnosis
Duchenne muscular dystrophy: the allelic, more severe dystrophinopathy from out-of-frame mutations, distinguished by earlier onset (before age 5), rapid progression, loss of ambulation by age 10 to…
- Diagnosis
Basis of diagnosis: confirmed by identifying an in-frame deletion, duplication, or point mutation in the dystrophin gene in a male patient with a compatible picture (proximal weakness, calf…
- Management
First step, baseline multidisciplinary evaluation: referral to a neuromuscular specialist, cardiologist, and physical/occupational therapist at diagnosis to establish baseline function, initiate…
- Complications
Dilated cardiomyopathy and heart failure: the leading cause of morbidity and mortality in Becker muscular dystrophy, which can progress even in patients with well-preserved skeletal muscle strength.
- Prognosis
Longer survival than Duchenne muscular dystrophy: life expectancy in Becker muscular dystrophy is meaningfully longer, often into the fifth or sixth decade or beyond, though it remains reduced…
- Prevention
No primary prevention of the genetic mutation: there is no way to prevent the underlying DMD gene mutation once inherited, given its X-linked genetic basis.
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