Spinal muscular atrophy (SMA) is a common, inherited, pediatric motor neuron disorder caused by insufficient SMN protein. As of yet, there is no good treatment for the disease. SMA has an incidence of ~1 in 10,000 newborns carrier frequency of 1 in 50, making it the most common inherited cause of infant mortality. Patients with severe SMA, or Werdnig-Hoffman disease, typically manifest weakness during the first 6 months of life. Such patients are so debilitated that they never sit independently, frequently succumbing to the disease before age 2 years. A much milder form of SMA, Kugelberg-Welander disease, with onset after 18 months of age, often during childhood and characterized by prolonged ambulation and a normal life expectancy, was described in 1956. In 1995 mutations in a novel gene, Survival of Motor Neuron 1 (SMN1), were determined to be the specific cause of SMA.
Carrier Frequency of Spinal Muscular Atrophy in a Large-scale Korean Population
