What are the symptoms of myotonic dystrophy?

Symptoms of myotonic dystrophy usually start when people are adolescents or young adults in their twenties or thirties. However, they can appear at any age, and vary in severity. Symptoms of myotonic dystrophy progress slowly. Myotonic dystrophy causes muscle weakness or wasting, especially in the muscles of the neck, face, and extremities, such as the lower legs, forearms, and hands. The faces of those with myotonic dystrophy appear hollow and droopy due to muscle weakness, and their eyelids may also begin to droop.
People with myotonic dystrophy often have myotonia, or prolonged stiffening of their muscles, because they are unable to voluntarily relax the muscles after a contraction. For example, they may not be able to release their grip on an object such as a drawer pull or doorknob.
They can also experience difficulty swallowing, due to weakening of the muscles used for swallowing. Muscles in the some internal organs, such as the intestines and uterus, also become weak. People with myotonic dystrophy may develop constipation or diarrhea, depending on the affected area of the digestive tract.
People with the most severe form of myotonic dystrophy may have cataracts, diabetes, mental retardation, daytime sleepiness, and difficulty sleeping at night. They may also have an irregular heartbeat, feel dizzy, or faint.