DMPK and myotonic dystrophy type 1: The difference in the CTG repeat size of the DMPK between the transmitting parent and the affected child was also lower in DM1-MC (−235; −280–0) compared with DM1-Fm (866; 612–905; p = 0.015 and 0.019) and DM1-FC (605; 10–1393; p = 0.005) (Figure 3).