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Population-Based Prevalence of Myotonic Dystrophy Type 1 Using Genetic Analysis of Statewide Blood Screening Program
Nicholas E Johnson1,2, Russell J Butterfield3,4, Katie Mayne3,4
1From the Department of Neurology (N.E.J.), Virginia Commonwealth University, Richmond; and Departments of Pediatrics (R.J.B., K.M., T.N., C.I., M.L.F.) and Nicholas.johnson@vcuhealth.org.
Neurology
|January 21, 2021
Summary
The genetic prevalence of myotonic dystrophy type 1 (DM1) is up to five times higher than previously estimated. This finding suggests that DM1 is likely underdiagnosed, highlighting the need for increased awareness and diagnostic efforts.
Area of Science:
- Genetics
- Neurology
- Public Health
Background:
- Myotonic dystrophy type 1 (DM1) is a genetic disorder caused by a CTG repeat expansion in the DMPK gene.
- Previous population estimates for DM1 prevalence range from 5 to 20 per 100,000 individuals.
- The actual prevalence may be higher due to potential underdiagnosis of this multisystemic disorder.
Purpose of the Study:
- To determine the genetic prevalence of CTG repeat expansions in the DMPK gene within an unbiased newborn cohort.
- To compare the observed prevalence with existing population estimates for DM1.
Main Methods:
- A cross-sectional study analyzed deidentified dried blood spots from consecutive births in New York (2013-2014).
- Triplet-repeat primed PCR and melt curve analysis screened for CTG repeat expansions in the DMPK gene.
- Expansion confirmation involved PCR fragment sizing via capillary electrophoresis, with prevalence calculated for repeat sizes ≥50.
Main Results:
- Out of 50,382 births, 24 individuals had a CTG repeat expansion ≥50, indicating DM1.
- The study found a DM1 prevalence of 4.76 per 10,000 births (1 in 2,100), significantly higher than prior estimates.
- An additional 96 samples (19.1 per 10,000) showed premutation range CTG expansions (35-49 repeats).
Conclusions:
- The prevalence of CTG repeat expansions in the DMPK gene is up to five times higher than previously reported.
- These findings suggest that DM1 is likely underdiagnosed in the general population.
- Increased awareness and improved diagnostic strategies are warranted for this multisystemic condition.
