DMPK and myotonic dystrophy type 2: Conversely to MC, myotonic dystrophy is an autosomal dominant multisystemic disease due to expansion of nucleotide repeats in the DMPK (DM1 or Steinert disease) or ZNF9 (DM2 or proximal myotonic myopathy or PROMM) genes (Meola, 2013; Meola and Cardani, 2014).