{"id":2154,"date":"2009-12-31T17:11:40","date_gmt":"2009-12-31T22:11:40","guid":{"rendered":"http:\/\/insidesurgery.com\/?p=2154"},"modified":"2009-12-31T17:28:23","modified_gmt":"2009-12-31T22:28:23","slug":"duchennes-muscular-dystrophy","status":"publish","type":"post","link":"https:\/\/insidesurgery.com\/2009\/12\/duchennes-muscular-dystrophy\/","title":{"rendered":"Duchenne’s Muscular Dystrophy"},"content":{"rendered":"

Pathophysiology<\/strong><\/p>\n

1)<\/strong> progressive muscle degeneration occurring in boys, due to absent dystrophin 2)<\/strong> Becker’s muscular dystrophy – less severe clinically; considered a variant of Duchenne’s (dystrophin is present but is smaller than normal)<\/p>\n

Signs and Symptoms<\/strong><\/p>\n

1)<\/strong> infants normal at birth, but within 4 years muscle weakness begins (especially in pelvic and shoulder girdles) 2)<\/strong> pseudohypertrophy of calf muscles 3)<\/strong> gait becomes clumsy (or ambulation is never obtained 4)<\/strong> Gowers’ sign 5)<\/strong> contractures in heel cords 6)<\/strong> progressive, painful scoliosis 7)<\/strong> cardiomyopathy 8)<\/strong> respiratory difficulties occur increasingly through teen years 9)<\/strong> patients are usually wheelchair boung by age 12 and usually die by age 21 (often due to pulmonary infection)<\/p>\n

Characteristic Test Findings<\/strong><\/p>\n

Laboratory<\/em> – 1)<\/strong> increased serum CK 2)<\/strong> prenatal and carrier genetic diagnoses are available<\/p>\n

Histology\/Gross Pathology<\/strong> <\/p>\n

1)<\/strong> breakdown of sarcolemma 2)<\/strong> degeneration and necrosis of muscle fibers 3)<\/strong> type 1 and 2 myofibrils attempt to repair and regenerate 4)<\/strong> eventual fibrosis and loss of skeletal muscle fibers 5)<\/strong> diminished\/absent dystrophin in muscle fibers 6)<\/strong> replacement of muscle fibers with fibrofatty connective tissue 7)<\/strong> sparing of muscle spindle fibers 8)<\/strong> abnormal presence of dystrophin cerebral cortex muscle<\/p>\n

Biochemistry<\/strong><\/p>\n

1)<\/strong> missing dystrophin results in inability of actin to bind to extracellular matrix 2)<\/strong> abnormal calcium influx across defective surface membrane elicits excessive contraction and eventual necrosis<\/p>\n

Inheritance\/Epidemiology<\/strong><\/p>\n

1)<\/strong> 70% X-linked; 30% sporadic 2)<\/strong> mulitple defects in gene (Xp21) have been described 3)<\/strong> occurs in 1\/3500 male births<\/p>\n

Treatment<\/strong><\/p>\n

1)<\/strong> palliative treatment with glucocorticoids slows progression for several years 2)<\/strong> gene therapy trials offer possible long-term palliation<\/p>\n

Tips for USMLE<\/strong><\/p>\n

1)<\/strong> Gowers’ sign is using hands to push up from floor 2)<\/strong> if the question mentions greatly increased serum CK, think Duchenne’s 3)<\/strong> if the question describes a previously normal 3 year-old boy whose gait has become more clumsy and whose calves seem to be overly muscular, think Duchenne’s<\/p>\n","protected":false},"excerpt":{"rendered":"

Pathophysiology 1) progressive muscle degeneration occurring in boys, due to absent dystrophin 2) Becker’s muscular dystrophy – less severe clinically; considered a variant of Duchenne’s (dystrophin is present but is smaller than normal) Signs and Symptoms 1) infants normal at birth, but within 4 years muscle weakness begins (especially in pelvic and shoulder girdles) 2) […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_exactmetrics_skip_tracking":false,"_exactmetrics_sitenote_active":false,"_exactmetrics_sitenote_note":"","_exactmetrics_sitenote_category":0,"_genesis_hide_title":false,"_genesis_hide_breadcrumbs":false,"_genesis_hide_singular_image":false,"_genesis_hide_footer_widgets":false,"_genesis_custom_body_class":"","_genesis_custom_post_class":"","_genesis_layout":"","footnotes":""},"categories":[63],"tags":[814,810,812,809,813,815,811],"yoast_head":"\nDuchenne's Muscular Dystrophy - InsideSurgery Medical Information Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/insidesurgery.com\/2009\/12\/duchennes-muscular-dystrophy\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Duchenne's Muscular Dystrophy - InsideSurgery Medical Information Blog\" \/>\n<meta property=\"og:description\" content=\"Pathophysiology 1) progressive muscle degeneration occurring in boys, due to absent dystrophin 2) Becker’s muscular dystrophy – less severe clinically; 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