Phenotypic variability and molecular genetics in proximal myotonic myopathy

Myotonic dystrophy type 2 (DM2) is an autosomal dominant inherited disorder with (CCTG)n repeat expansion in intron 1 of the CNBP gene.

We studied the first 16 Greek DM2 patients who had undergone thorough evaluation.

The age at diagnosis ranged from 38 to 69 years. The initial symptoms were proximal weakness, myalgias, and myotonia. Clinical myotonia was elicited in 10 patients, whereas electromyographic myotonic discharges were observed in almost all patients. Subcapsular cataract was frequently present, but cardiac arrhythmias were rare.

In this study of Greek DM2 patients, proximal weakness was the most common initial symptom. Myalgias were also reported in a few patients, yet myotonia was not a major complaint. Although DM2 is considered relatively benign, there are patients who may be affected severely. Thus, a high index of suspicion must be maintained to make a timely diagnosis, especially in those of reproductive age.