Table 2.

Correlation of Phenotype and CTG Repeat Length in Myotonic Dystrophy Type 1

PhenotypeClinical SignsCTG Repeat Size 1, 2Age of OnsetAverage Age of Death
Mutable normal
(premutation) 		None35-49NANA
Mild
  • Cataracts
  • Mild myotonia
50-~15020-70 yrs60 yrs to normal life span
Classic
  • Weakness
  • Myotonia
  • Cataracts
  • Balding
  • Cardiac arrhythmia
~100-~1,00010-30 yrs48-55 yrs
Congenital
  • Infantile hypotonia
  • Respiratory deficits
  • Intellectual disability
  • Classic signs in adults
>1,000 3Birth to 10 yrs45 yrs 4

NA = not applicable

1.

CTG repeat sizes are known to overlap between phenotypes.

2.

Normal CTG repeat size is 5-34.

3.

Redman et al [1993] reported a few individuals with congenital DM1 with repeats between 730 and 1,000.

4.

Does not include neonatal deaths

From: Myotonic Dystrophy Type 1

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