DMPK and myotonic dystrophy type 1: The current study sought to (a) ascertain if increasing disease severity (as measured by the muscle impairment rating scale (MIRS)) in DM1 from the EU FP7 OPTIMISTIC cohort are associated with changes in the blood transcriptome and (b) establish if these changes in mRNA expression and associated biological pathways were also observed in an independently performed DMBDI microarray dataset in blood (with equivalent MIRS/DMPK repeat length).