Congenital and childhood myotonic dystrophy: Current aspects of disease and future directions

Table 1 Myotonic dystrophy type 1 clinical phenotypes

Phenotype	Clinical characteristics	CTG repeat length	Age of onset (yr)
Premutation	Not applicable	38-49	Not applicable
Mild/late onset adult	Mild myotonia	50-100	20 to 70
	Cataracts
Classical adult	Myotonia	50-1000	10 to 30 (median 20 to 25)
	Muscle weakness
	Cataracts
	Conduction defects
	Insulin resistance
	Respiratory failure
Childhood onset	Facial weakness	> 800	1-10
	Cognitive defects
	Psychosocial issues
	Incontinence
Congenital	Hypotonia	> 1000	Birth
	Respiratory distress
	Cognitive defects
	Motor and developmental delay
	Feeding difficulties