Science News: Myotonic Muscular Dystrophy Type 2 in CT, USA: A Single-Center Experience With 50 Patients

Submitted by: Francisco Gomez, MD

Roy B, Wu Q, Whitaker CH, Felice KJ. Myotonic muscular dystrophy type 2 in CT, USA: A single-center experience with 50 patients. J Clin Neuromuscul Dis. 2021;22(3):135-146. doi:10.1097/CND.0000000000000340

Summary: Myotonic muscular dystrophy type 2 (DM2) is a an autosomal dominant genetic disease stemming from expansion of the first intron of the Cellular Nucleic acid Binding Protein (CNBP) gene which encodes for a zinc finger protein. This disease tends to course with wasting muscle weakness, characteristic myotonia, and cataracts.

The authors report a 27 year, single center case series involving 50 patients diagnosed with Myotonic Dystrophy type 2, reporting incidence and prevalence of several findings:

Age of onset ranged 15-72 years, with an average time from clinical debut to diagnosis of 7.4 years, furthermore:
•    18% presented with clinical myotonia, however, electromyographic myotonia was found in 97% of patients.
•    62% debuted with proximal extremity weakness.
•    30% presented generalized weakness while 20% exhibited no weakness at all.
•    There was no correlation between number of repeats and pathologic changes, however there was a correlation noted between degree of muscle weakness and muscle pathologic changes.
•    A 1% yearly decline in Medical Research Council scores was observed in 21 patients followed for 2 or more years.