Original Article
Congenital Myotonic Dystrophy: Canadian Population-Based Surveillance Study

https://doi.org/10.1016/j.jpeds.2012.12.070Get rights and content

Objectives

To determine the incidence and neonatal morbidity and mortality of congenital myotonic dystrophy (CDM) in Canada.

Study design

The study has 2 phases. A 5-year prospective monthly surveillance of incident cases of CDM conducted via the Canadian Pediatric Surveillance Program, from March 1, 2005-February 28, 2010, and a 5-year cohort study of eligible incident cases, which is ongoing and not the subject of this report.

Results

A total of 121 cases were reported, with 38 confirmed as CDM. The incidence of CDM in Canada is 2.1/100 000 (1/47 619) live births. The cases were reported from 8 provinces and 1 territory. The highest reported incidence was Ontario with 15, followed by British Columbia with 7, and Quebec with 6. External validation of cases was performed. The trinucleotide repeat level varied from 550-3100. Twenty-two (58%) of the children were the index cases for their families. Seventeen children are currently enrolled in the ongoing cohort study.

Conclusion

Surveillance and prospective examination of CDM at a population level is important, as the impact of this rare disease is systemic, chronic, and associated with significant morbidity and mortality throughout childhood.

Section snippets

Methods

A 5-year surveillance study, from March 1, 2005-February 28, 2010, was undertaken through the CPSP. This program is a partnership between the Canadian Pediatric Society and the Public Health Agency of Canada and has been successfully collecting data on rare diseases since 1996 (http://www.cps.ca/English/surveillance/cpsp/index.htm). The CPSP surveys over 2500 pediatricians and pediatric subspecialists each month through a mail out, which is a single-page form listing of all the rare diseases

Results

The average annual CPSP response rate during the study was 80% (range 69%-100%, Table I). Throughout the CPSP study, there were 121 cases reported. Of these, 38 met the inclusion criteria and were confirmed as incident cases. Table II demonstrates that one-third of the reported cases were duplicates, meaning 2 different pediatricians reported the same child. This was easily evident by timing of reporting, date of birth, and location. Two cases are still of unresolved (pending or unknown) status

Discussion

Our study indicates that the incidence of CDM in Canada is 2.1 children for every 100 000 live births (1/47 619 live births). This incidence figure is lower than previously reported; however the population-based active surveillance carried out in this study is an important methodologic advance over past incidence studies, described in more detail below. Although the incidence of CDM has been estimated at 1 in every 3500 to 16 000 births by others, these have not been national population-based

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    Funded by the William Singeris Center for Myotonic Dystrophy at the Child Health Research Institute. The authors declare no conflicts of interest.

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