Overview Snapshot A 4-year-old boy is brought to his pediatrician by his mother for muscle weakness. She reports that he has trouble running with his friends and climbing the stairs. She also states that the patient has increased difficulty arising from a seated position on the ground and walks in a "waddling" way. On physical exam, there is significant proximal muscle weakness and pseudohypertrophy of the bilateral calves. He also has Gower sign. Laboratory testing is notable for a significantly elevated creatine kinase and aldolase. A sample is obtained for genetic analysis of the dystrophin gene. (Duchenne muscular dystrophy) Introduction Clinical definition inherited disorder of skeletal muscle leading to progressive muscle weakness Epidemiology incidence Duchenne muscular dystrophy login to view 1 more bullet Becker muscular dystrophy login to view 1 more bullet demographics male children login to view 1 more bullet Etiology X-linked recessive mutation in the dystrophin gene Duchenne muscular dystrophy login to view 2 more bullets Becker muscular dystrophy login to view 3 more bullets Pathogenesis normal biology dystrophin is one of the largest human genes and appears to be involved in login to view 3 more bullets dystrophin is expressed in cardiac, skeletal, and neural tissue pathology absent or decreased function of dystrophin leads to cycles of muscle fiber degeneration and regeneration login to view 1 more bullet Prognosis Duchenne muscular dystrophy mean age of death is 25-30 years of age and death results from login to view 2 more bullets Becker muscular dystrophy less severe than Duchenne muscular dystrophy Presentation Symptoms progressive muscle weakness most severe in the proximal muscles and lower extremity waddling gait Physical exam Gower sign a patient using their upper extremity to stand login to view 1 more bullet calf pseudohypertrophy lumbar lordosis hypo- or areflexia Studies Labs ↑ serum creatine kinase ↑ aldolase, alanine transaminase, and aspartate transaminase Genetic testing confirms the diagnosis Dystrophin analysis Duchenne muscular dystrophy complete or almost complete loss of dystrophin Becker muscular dystrophy dystrophin with abnormal molecular weight reduced quantity of dystrophin Biopsy muscle fibril degeneration, regeneration, and isolated fiber hypertrophy muscle replacement with fat and connective tissue performed if genetic testing is negative Differential Limb-girdle muscular dystrophy Spinal muscular atrophy Treatment Management approach treatment for both Duchenne and Becker muscular dystrophy is multidisciplinary to manage symptoms and complications Medical glucocorticosteroids indication login to view 1 more bullet drugs login to view 2 more bullets adverse effects login to view 3 more bullets Complications Muscular wheel chair bound Cardiac dilated cardiomyopathy arrhythmia Orthopedic fractures secondary to falling