Which age groups have the highest prevalence of spinal muscle atrophy (SMA)?

Updated: May 04, 2020
  • Author: Ashish S Ranade, MBBS, MS, MRCS; Chief Editor: Jeffrey A Goldstein, MD  more...
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The three different types of SMA that occur in the pediatric population are genetically similar but differ with respect to patient age at presentation and clinical course, as follows:

  • Type I (Werdnig-Hoffmann disease) - This acute infantile SMA is usually identified in patients from birth to age 6 months; it is the most severe and common form of the disease, accounting for 60% of all cases of SMA, and it is often fatal early in life
  • Type II - This chronic infantile SMA is diagnosed in infants aged 6-24 months
  • Type III (Kugelberg-Welander disease) - This type of SMA is diagnosed in children aged 2-15 years

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