- spinal muscular atrophy
- (SMA)a hereditary condition in which cells of the spinal cord die and the muscles in the arms and legs become progressively weaker. The gene responsible has been located: in affected children it is inherited as a double recessive. SMA usually develops between the ages of 2 and 12. Eventually the respiratory muscles are affected and death usually results from respiratory infection. Most affected individuals are wheelchair-bound by the age of 20 and few survive beyond the age of 30. Infantile spinal muscular atrophy is an acute aggressive form of the condition (see Werdnig-Hoffmann disease).
Medical dictionary. 2011.