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

Approximately 700 adult participants (18 to 70 years old, inclusive) with DM1 will be enrolled at 15 centers (up to 70 patients will be recruited at each site). No treatment will be administered as part of this study. Participants will receive standard of care as determined by the investigators. Study visits occur at baseline/0 months, 12 months, and 24 months. Few restrictions are placed on participation in the study because the investigators aim to capture the full spectrum of disease severity. Muscle biopsy sub-study: Studies of splicing biomarkers in muscle biopsy samples will be conducted on a subset of 95 participants. These participants will have an additional study visit at 3 months. Longitudinal muscle biopsy sub-study: Up to 30 individuals who have had a prior muscle biopsy as part of a DMCRN study will be asked to undergo another biopsy greater than 24 months after the prior biopsy. These participants will have an additional ad hoc biopsy visit. COVID-19 sub-study: To evaluate severity of illness and response to COVID-19 vaccination in DM1 patients compared to corresponding data available about the general population, END-DM1 study participants will be asked to complete a one-time survey about COVID-19 experiences. A subset of those participants' blood samples will be analyzed to understand immunoglobulin response to infection and vaccination in DM1 patients. Actigraphy sub-study: To assess daily physical activity in individuals with DM1 and evaluate physical activity changes over a 12-24 month period related to disease progression, a subset of participants will be asked to wear a small, wireless activity monitor while performing functional assessments described in the main study. Those participants will be asked to wear the activity monitor for 7 days following their research visit. Those participants will be asked to complete additional questionnaires. Handheld Dynamometry sub-study: To evaluate additional muscle strength methods, a subset of participants will be asked to complete additional strength testing using either the MEDup or MicroFET handheld dynamometry device on the same day as their END-DM1 main study visit. Those participants will be asked to return to the clinic for a second visit within 10 days of the END-DM1 study visit to repeat the handheld dynamometry assessments and complete additional strength measures.