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Lise Caget Bodor Gergely. Spinal muscular atrophy. SMA. JPEMS 2014. Introduction. A heterogenous group of disorders . Various degrees of severity Collective incidence of 1/10,0 00 . Most common genetic cause of infant death. Signs&Symptoms. Areflexia.
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Lise Caget Bodor Gergely Spinal muscular atrophy SMA JPEMS 2014
Introduction • A heterogenous group of disorders. • Various degrees of severity • Collective incidence of 1/10,000. • Most common genetic cause of infant death.
Signs&Symptoms • Areflexia. • Overall muscle weakness, poor muscle tone. • Weight lower than normal. • Difficulty achieving developmental milestones. • Weak respiratory muscles.
Phisiopathology • The disease is characterized by degeneration of the anterior horn cells of the spinal cord (motorneurons).
Physiopathology • Denervation: the skeletal muscles loose their input from the central nervous system. • Denervated muscles undergo progressive atrophy. (Flaccid paralysis)
Physiopathology • The cell death is caused by the absence of two proteines. • SMNP: Survival motor neuron protein. • NAIP: Neuronal apoptosis inhibitory protein. Deleted in 45% of individuals with Type 1 SMA, and in up to 20% of those with Type 2 and Type 3.
SMA1 : Werdnig-Hoffmandisease • The most common and the most severe • Present at birth or in the first 6 months of life • Severe hypotonia and lack of spontaneous mouvement • Fetal mouvement reduced • Muscular weakness affects swallowing and respiratory functions • Death within the first two years of life.
SMA 2 • Less severe • Age of onset between 6 and 18 months • Muscle weakness and hypotonia • Kids can sit but they can't walk • Survival until early adult life
SMA 3: Kugelberg-Welander disease • Present after 18 months • Patients are able to walk • Progressive muscular weakness leads to use a wheelchair by early adult life • Recurrent respiratory infections and scoliosis due to the weakness of spinal muscles
SMA 4 • Adult type : usually manifests after 30 years • Gradual weakening of muscles • Requiring the patient to use a wheelchair for mobility • Rare complications • Normal life expectancy
References • http://jadonshope.org/index.php?page=the-genetics-of-sma • http://withfriendship.com/user/levis/muscle-atrophy.php • http://www.fightsma.org/ • Sian Ellard BSc PhD MRCPath, Peter D Turnpenny BSc MB ChB FRCP FRCPCH: Emery's Elements of Medical Genetics