Spinal Muscular Atrophy

Reference work entry

Spinal muscular atrophy (SMA) is a disorder characterized by degeneration of lower motor neurons and occasionally bulbar motor neurons leading to progressive limb and trunk paralysis as well as muscular atrophy. It is a clinically and genetically heterogeneous group of neuromuscular diseases. It is the second most common lethal autosomal recessive disorder after cystic fibrosis in Caucasian populations with an overall incidence of 1 in 10,000 live births and a carrier frequency of approximately 1 in 50 (Biros and Forrest 1999).

Synonyms and Related Disorders

Adult SMA; Arthrogryposis multiplex congenita-SMA; Congenital axonal neuropathy; Dubowitz disease; Kugelberg-Welander disease; Werdnig-Hoffman disease

Genetics/Basic Defects

  1. 1.
    1. a.

      Autosomal recessive in most cases (SMA1, SMA2, SMA3)

    2. b.

      Autosomal dominant in both juvenile and adult form, representing 2% of infantile and about 30% of adult SMA

  2. 2.

    Caused by mutation or deletion of Survival Motor Neuron-1 (SMN1)

  3. 3.



Spinal Muscular Atrophy Survive Motor Neuron Lower Motor Neuron Anterior Horn Cell Spinal Muscular Atrophy Patient 
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