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Genetic and Rare Diseases Information Center (GARD)

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Spinal muscular atrophy type 2


Other Names for this Disease
  • Muscular atrophy, spinal, infantile chronic form
  • Muscular atrophy, spinal, intermediate type
  • SMA2
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Overview



What is spinal muscular atrophy type 2?

What are the signs and symptoms of spinal muscular atrophy type 2?


What is spinal muscular atrophy type 2?

Spinal muscular atrophy type 2 (SMA II) is part of a group of disorders that affect the control of muscle movements. It is caused by a loss of specialized nerve cells, called motor neurons, in the spinal cord and the part of the brain that is connected to the spinal cord (the brainstem). The loss of motor neurons leads to weakness and wasting (atrophy) of muscles used for activities such as crawling, walking, sitting up, and controlling head movement. SMA II is characterized by muscle weakness that develops in children between ages 6 and 12 months. Children with SMA II can sit without support, although they cannot stand or walk unaided.[1] Finger trembling and general weakness are common. It is typically caused by mutations in the SMN1 gene and is inherited in an autosomal recessive manner.[2]
Last updated: 11/28/2011

What are the signs and symptoms of spinal muscular atrophy type 2?

The signs and symptoms of spinal muscular atrophy type 2 (SMA II) typically become apparent between 6 and 12 months of age, although poor muscle tone may be noticed at birth or within the first few months of life. Affected individuals may slowly gain some motor milestones, but usually do not have motor milestones beyond the ability to sit independently when placed in a sitting position. Finger trembling and general poor muscle tone are almost always present. Affected individuals generally lose the ability to sit independently by their mid-teens, on average. The life expectancy of affected individuals is not exactly known; some individuals may live into adolescence, while others may live to the third or fourth decade of life.[2] For information about the signs and symptoms of spinal muscular atrophy in general, click here.
Last updated: 11/28/2011

References
  1. Spinal muscular atrophy. Genetics Home Reference (GHR). December 2009; http://ghr.nlm.nih.gov/condition/spinal-muscular-atrophy. Accessed 5/13/2011.
  2. Thomas W Prior, Barry S Russman. Spinal Muscular Atrophy. GeneReviews. January 27, 2011; http://www.ncbi.nlm.nih.gov/books/NBK1352/. Accessed 11/28/2011.