Estab Biomarkers and Clinical Endpoints in Myotonic Dystrophy Type 1 (END-DM1)

Inclusion criteria: * Age 18 to 70 (inclusive) * Competent to provide informed consent * Clinical diagnosis of DM1 based on research criteria1 or positive genetic test * Comment: The clinical research criteria require myotonia, muscle weakness in a characteristic distribution, and history of similar findings in a first degree relative. Genetic testing confirmed the diagnosis of DM1 in \> 99% of individuals who satisfied these criteria.2 Exclusion criteria: * Symptomatic renal or liver disease, uncontrolled diabetes or thyroid disorder, or active malignancy other than skin cancer. * Current alcohol or substance abuse * Concurrent enrollment in clinical trial for DM1, or participation in trial within 6 months of entry. * Concurrent pregnancy or planned pregnancy during the course of the study. * Concurrent medical condition that would, in the opinion of the investigator or clinical evaluator, compromise performance on study measures. * Note: non-ambulatory participants are not excluded, but are limited to \<15% of enrollment. Inclusion criteria for participants in the muscle biopsy sub-study: • Of the 95 patients undergoing the tibialis anterior muscle biopsy, at least half will have at least moderate weakness of ankle dorsiflexion, defined as MRC score ≤ 4+. This is in order to obtain a muscle tissue sample in a person more severely affected with myotonic dystrophy. Approximately 10 patients at each site will undergo the muscle biopsy. Exclusion criteria for 95 participa…