Korean J Pediatr.  2019 Feb;62(2):55-61. 10.3345/kjp.2018.06919.

Genotype-phenotype correlations in pediatric patients with myotonic dystrophy type 1

Affiliations
  • 1Department of Pediatrics, Yonsei University College of Medicine, Seoul, Korea. ymleemd@yuhs.ac

Abstract

PURPOSE
Myotonic dystrophy, also known as dystrophia myotonica (DM), is an autosomal dominant disorder with 2 genetically distinct forms. DM type 1 (DM1) is the more common form and is caused by abnormal expansion of cytosine/thymine/guanine (CTG) repeats in the DM protein kinase (DMPK) gene. Our study aimed to determine whether the age of onset is correlated with CTG repeat length in a population of pediatric patients with DM1.
METHODS
We retrospectively identified 30 pediatric patients with DM1 that underwent DMPK testing, of which the clinical data of 17 was sufficient. The cohort was divided into 2 subgroups based on the clinical phenotype (congenital-onset vs. late-onset) and number of CTG repeats ( < 1,000 vs. ≥1,000).
RESULTS
We found no significant difference between the age of onset and CTG repeat length in our pediatric patient population. Based on clinical subgrouping, we found that the congenital-onset subgroup was statistically different with respect to several variables, including prematurity, rate of admission to neonatal intensive care unit, need for respiratory support at birth, hypotonia, dysphagia, ventilator dependence, and functional status on last visit, compared to the late-onset subgroup. Based on genetic subgrouping, we found a single variable (poor feeding in neonate) that was significantly different in the large CTG subgroup than that in the small CTG subgroup.
CONCLUSION
Clinical variables exhibiting statistically significant differences between the subgroups should be focused on prognosis and designing tailored management approaches for the patients; our findings will contribute to achieve this important goal for treating patients with DM1.

Keyword

Myotonic dystrophy type 1; Genotype; Phenotype; CTG repeat; Age of onset

MeSH Terms

Age of Onset
Cohort Studies
Deglutition Disorders
Genetic Association Studies*
Genotype
Humans
Infant, Newborn
Intensive Care, Neonatal
Muscle Hypotonia
Myotonic Dystrophy*
Myotonin-Protein Kinase
Parturition
Phenotype
Prognosis
Retrospective Studies
Ventilators, Mechanical
Myotonin-Protein Kinase
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