Spinal muscular atrophy (SMA) is a group of neuromuscular disorders that result in the loss of motor neurons and progressive muscle wasting. The severity of symptoms and age of onset varies by the type. Some types are apparent at or before birth while others are not apparent until adulthood. All generally result in worsening muscle weakness associated with muscle twitching. Arm, leg and respiratory muscles are generally affected first. Associated problems may include problems with swallowing, scoliosis, ...
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