Duchenne and Becker muscular dystrophy

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Target exams

Red flags

• A boy with a creatine kinase above 10,000 units per litre has a dystrophic process until genetic testing proves otherwise
• Never give suxamethonium or volatile anaesthetic agents to a boy with a dystrophinopathy, because the risk is anaesthesia-induced rhabdomyolysis and hyperkalaemic arrest
• A glucocorticoid-treated boy who is acutely unwell or perioperative needs stress-dose hydrocortisone, because chronic steroids suppress the adrenal axis
• A DMD boy with new breathlessness, orthopnoea, or morning headaches has ventilatory failure until his peak cough flow and overnight oximetry are checked
• Any dilated cardiomyopathy in a boy or young man needs a creatine kinase and dystrophin analysis, because Becker may present with heart failure before weakness
• Loss of the ability to walk, rise from the floor, or climb stairs in a previously steady boy signals the transition into the non-ambulatory phase and prompts wheelchair and scoliosis planning

Life stages

Care settings

Clinical exam formats

Board mappings

• Recognises Duchenne muscular dystrophy in a boy with delayed motor milestones, calf pseudohypertrophy, Gowers sign, and a creatine kinase above 10,000 units per litre
• States that Duchenne and Becker muscular dystrophy are X-linked recessive dystrophinopathies caused by mutations in the DMD gene with absent or reduced dystrophin
• Identifies glucocorticoids as the disease-modifying backbone and names prednisolone 0.75 mg per kg per day or deflazacort 0.9 mg per kg per day
• Explains the reading-frame hypothesis, the dystrophin-associated glycoprotein complex, and the degeneration-regeneration-fibrosis cascade that produces progressive weakness
• Coordinates the multidisciplinary care of glucocorticoids, cardiac surveillance with angiotensin-converting-enzyme inhibition, and respiratory surveillance with spirometry and non-invasive ventilation
• Selects precision therapies by mutation, including exon-skipping antisense oligonucleotides, nonsense-readthrough, and AAV micro-dystrophin gene therapy, and appraises the FOR-DMD and EMBARK trials
• The creatine kinase is markedly elevated, typically above 10,000 units per litre, and the diagnosis is confirmed by genetic testing with multiplex ligation-dependent probe amplification
• Prednisolone 0.75 mg per kg per day or deflazacort 0.9 mg per kg per day is started at the motor plateau and delays loss of ambulation
• Suxamethonium and volatile anaesthetic agents are contraindicated because of anaesthesia-induced rhabdomyolysis and hyperkalaemic arrest
• Assesses the boy with a dystrophinopathy across the gait, the Gowers sign, the timed function tests, the contractures, and the cardiorespiratory surveillance
• Counsels the family on the genetic inheritance, the disease trajectory, the glucocorticoid benefits and adverse effects, and the transition to adult neuromuscular services
• Builds the multidisciplinary plan that runs neurology, cardiology, respiratory, rehabilitation, endocrine, and psychosocial care together
• Level 1: Recognition of the boy with a high creatine kinase, delayed motor milestones, and pseudohypertrophy who needs urgent genetic testing
• Level 2: Application of glucocorticoid therapy, cardiac and respiratory surveillance, and bone protection in the ambulatory and non-ambulatory phases
• Level 3: Coordination of the neuromuscular multidisciplinary team, precision genetic therapies, and the transition across the lifespan
• The genetics, the dystrophin protein, the reading-frame hypothesis, and the Duchenne versus Becker severity gradient
• The creatine kinase, the genetic confirmation, and the glucocorticoid doses and their adverse effects
• The cardiac and respiratory surveillance thresholds and the precision therapies of exon-skipping and gene therapy
• Structured assessment of the boy with a dystrophinopathy across the gait, the Gowers sign, the timed function, and the contractures
• Communication of the diagnosis, the inheritance, the prognosis, and the multidisciplinary plan with the family
• Recognition and management of the cardiac and respiratory complications across the disease trajectory
• Duchenne muscular dystrophy as an X-linked recessive dystrophinopathy presenting with delayed motor milestones, pseudohypertrophy, Gowers sign, and a creatine kinase above 10,000
• Genetic confirmation, glucocorticoid therapy, and the cardiac, respiratory, and bone surveillance that define modern care
• The precision therapies of exon-skipping, nonsense-readthrough, and AAV gene therapy selected by mutation
• Recognition of the dystrophinopathies and the priority of an early creatine kinase and genetic confirmation
• Application of glucocorticoids, cardiorespiratory surveillance, and bone protection across the disease trajectory
• Coordination of the neuromuscular multidisciplinary team and the transition to adult services
• Canadian approach to the dystrophinopathies with an early creatine kinase and multiplex ligation-dependent probe amplification
• Glucocorticoid therapy with prednisolone or deflazacort, cardiac and respiratory surveillance, and bone health
• Precision genetic therapies and the appraisal of the FOR-DMD and EMBARK trial evidence