Development of Quantitative Muscle Imaging as a Biomarker of Disease Endpoints in Myotonic Dystrophy

Inclusion Criteria:

DM subjects

* Age 18 - 65 years
* Diagnosis of DM1 or DM2 by clinical or genetic criteria. If DM1 or DM2 was diagnosed by clinical criteria, a first-degree relative must have genetic testing confirmation and sign a genetic consent form to release their genetic information
* Clinically affected, as defined by muscle weakness or myotonia
* Ambulate independently (a walker is not permitted)
* Able to provide informed consent for participation in the study

Control subjects

* Age 18 - 65 years old
* Healthy as defined by no significant medical or neurological conditions
* Able to provide informed consent for participation in the study

Exclusion Criteria:

* Cardiac pacemaker, defibrillator, metal implants, or other contraindications for MRI
* Use of anabolic or catabolic agents within one year of entry
* History of lumbar spine or leg surgery, lumbar radiculopathy, or peripheral neuropathy
* BMI \> 35 because obesity compromises positioning on the MR scanner
* Pregnancy
* For muscle biopsy, history of bleeding disorders or on anticoagulation. Subjects taking nonsteroidal anti- inflammatory agents will be asked to discontinue these medications 7 days prior to muscle biopsy.