Myotonic dystrophy type 1: A comparison between the adult- and late-onset subtype.

Although muscular phenotype was milder in late-onset compared with adult-onset DM1, the prevalence of conduction delay was comparable. Moreover, subtype was unable to predict the presence of cardiac conduction delay. Although adult-onset patients had an increased risk of having an NIV indication, 17% of late-onset patients required NIV. Despite different muscular phenotypes, screening for multiorgan involvement should be equally thorough in late-onset as in adult-onset DM1.