DMCRN-02-001: Assessing Pediatric Endpoints in DM1

Inclusion Criteria:

• CDM group:

• Age neonate to 3 years 11 months at enrollment.

• A diagnosis of CDM, which is defined as children having symptoms of myotonicdystrophy in the newborn period (<30 days), such as hypotonia, feeding orrespiratory difficulty, requiring hospitalization to a ward or to the neonatalintensive care unit for more than 72 hours; and a genetic test confirming anexpanded trinucleotide (CTG) repeat in the DMPK gene in the child or mother. Anexpanded CTG repeat size in the child is considered greater than 200 repeats orE1-E4 classification (E1= 200-500, E2=500-1,000, E3=1,000-1,500, E4>1,500).

• Guardian is willing and able to sign consent and follow study procedures

• ChDM Group:

• Age 1 to 4 years 11 months at enrollment.

• A diagnosis of ChDM, which is defined as symptoms associated with DM1, absenceof symptoms at birth, and a genetic test confirming an expanded trinucleotide (CTG) repeat in the DMPK gene in the child or mother.12 An expanded CTG repeatsize in the child is considered greater than 200 repeats or E1-E4classification (E1= 200-500, E2=500-1,000, E3=1,000-1,500, E4>1,500).

• Guardian willing and able to sign consent and follow study procedures

Exclusion Criteria: (Both groups)

• Any other non-DM1 illness that would interfere with the ability or results of thestudy in the opinion of the site investigator

• Significant trauma within one month

• Internal metal or devices (exclusion for DEXA component)

• History of bleeding disorder or platelet count <50,000

• History of reaction to local anesthetic