Intron 2 retention in RFC1 pre-mRNA across various tissues has been identified in patients, which is known as a common event associated with other disease-causing guanine-cytosine-rich intronic expansions, like myotonic dystrophy type 2 and C9orf72-amyotrophic lateral sclerosis (4). This evidence concerns the gene RFC1 and Proximal myotonic myopathy.