Myotonic Muscular Dystrophy

          The most common form of muscular dystrophy in adults, both men and women and it usually appears any time from early childhood to adulthood. In rare cases, it appears in newborns.Myotonic dystrophy is characterized by progressive muscle wasting and weakness. People with this disorder often have prolonged muscle contractions (myotonia) and are not able to relax certain muscles after use. For example, a person may have difficulty releasing their grip on a doorknob or handle. Also, affected people may have slurred speech or temporary locking of their jaw. This symptom is usually worse in cold temperatures. The disease causes muscle weakness and also affects the central nervous system, heart, gastrointestinal tract, eyes, and hormone-producing glands. In most cases, daily living isn't restricted for many years. Those with myotonic muscular dystrophy have a decreased life expectancy.Myotonic dystrophy affects at least 1 in 8,000 people worldwide.

http://ghr.nlm.nih.gov/condition/myotonic-dystrophy

http://www.webmd.com/children/understanding-muscular-dystrophy-basics