Table 2

Comparative features of myotonic dystrophy type 1 (DM1) and type 2 (DM2) (adapted from Washington Neuromuscular website http://neuromuscular.wustl.edu/)

FeatureDM 1DM 2
General
 EpidemiologyWidespreadEuropean
 Onset age (years)0 to adult8–60
 Anticipation+Mild
 Congenital form+
Muscle
 Weakness
  Face++++
  Ptosis++++
  Sternomastoid++++
  Proximal legsLate+++
  Distal+++Hands
  Any location++
 Muscle pain++++
 Myotonia++
 Calf hypertrophy+
Systemic
 Cataracts+++++
 Balding++++
 Cardiac arrhythmias++++
 Gonadal failure++++
 Hypersomnia++++
 Hyperhidrosis++++
 Cognitive disorder+ to ++++
Laboratory
 Hyperinsulinaemia+++++
 EMG: myotonia++
 Chromosome19q13.33q21
 Mutated geneDMPKZNF9
 Mutation typeCTG repeatsCCTG repeats
 Repeat size50–4000mean ∼5000