Table 1.

Summary of Repeat Range, Penetrance, Age of Onset, and Phenotypes

Phenotype	Most prominent clinical symptoms	Repeat range	Age of Onset	Life Span	Penetrance and Anticipation (Yes/No)
Pre-mutation	None	38–49	-	Normal	At increased risk of penetrance Uncertain
Late-onset DM1	Cataracts, hypersomnia, myotonia	100–600	>40 years	Normal	Full Penetrance Yes
Adult DM1	Myotonia, cardiac arrhythmias, hypersomnia, gastrointestinal difficulties, muscle weakness and wasting, cataracts, male hypogonadism, insulin resistance, cognitive challenges, left ventricular dysfunctions	250–750	20–40 years	Shortened	Full Penetrance Yes
Juvenile DM1	Similar symptoms as adult DM1 but more severe	400–800	10–20 years	Shortened	Full Penetrance Yes
Infantile DM1	Similar symptoms as congenital DM1 but less severe	500–1100	1 mo. – 10 years	Shortened	Full Penetrance Yes
Congenital DM1	Developmental defects, hypotonia, respiratory insufficiency, cardiac defects, severe cognitive challenges, facial dysmorphism, dysphagia	750–1400	Birth	At increased risk of infant mortality or shortened	Full Penetrance Yes
DM2	Proximal muscle weakness and wasting, cognitive challenges, cardiac arrhythmias, myalgic pain, hypertension	100–10,000	Adult	Normal	Uncertain