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Spinal Muscular Atrophy

  • Hans Scheffer
Part of the Methods in Molecular Medicine™ book series (MIMM, volume 92)

Abstract

The spinal muscular atrophies are a clinically and genetically heterogeneous group of neuromuscular disorders caused by degeneration of anterior horn cells. In proximal spinal muscular atrophy (SMA), the muscles of the extremities closest to the trunk are affected earlier and more severely. SMA is clinically classified into four types: acute or Werdnig-Hoffmann disease, intermediate, mild or Kugelberg-Welander disease, and adult (SMA types I, II, III, and IV, respectively) (1,2). The clinical criteria are summarized in Table 1. With an estimated incidence of ∼1/10,000 (3, 4, 5, 6, 7), and a carrier frequency of 1/40–1/60 (8,9), the SMAs are among the most frequent autosomal recessive hereditary disorders, and the incidence appears to be similar in different populations studied.
Table 1

Criteria for Clinical Classification of SMA Patients

Clinical subtype

Age of Onset (in months)

Motor milestones

Death (in years)

SMA type I SMA type II SMA type III

<6 <18 >18

Never sit unaided Never walk unaided Stand unaided

<2 >2 adult

Keywords

Gene Conversion Spinal Muscular Atrophy Carrier Testing Spinal Muscular Atrophy Patient SMN1 Gene 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Humana Press Inc. 2004

Authors and Affiliations

  • Hans Scheffer
    • 1
  1. 1.Department of Human Genetics, DNA Diagnostic DivisionUniversity Medical Centre NijmegenNijmegenThe Netherlands

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