Adult-Onset Myotonic Dystrophy: DM1
With adult-onset DM1, symptoms can appear from late adolescence through old age, and usually worsen over time. Depending on severity of symptoms, patients with adult DM1 may be categorized as having either the mild or classical form of the disease.
Mild
Individuals with the mild form of adult-onset DM1 are often not aware they have the disorder. Muscle symptoms (if any) may be attributed to general stiffness or arthritis. Non-muscle symptoms tend to be moderate and are often diagnosed and treated as independent issues (e.g., cataracts or frontal balding in men).
These individuals are unlikely to be diagnosed as having myotonic dystrophy unless a family member is identified with a more severe form of the disease and testing is initiated.
Classical
Individuals with classical adult-onset DM1 often first receive medical attention because of muscle weakness and myotonia (difficulty relaxing a muscle) in the arms, face, and legs. Muscle wasting (atrophy) and persistent muscle pain may also be present, particularly in later life.
Development of facial muscles and the skull are usually set by age 25. If muscle wasting occurs after this age in an adult with DM1, the face can become drawn-out, droopy, or malnourished looking. Due to muscle weakness, eventually some people lose their ability to smile. Experienced doctors can often predict the diagnosis of DM1 solely based on facial appearance.
Other muscle issues can result in a range of complications. Mobility can be restricted and assistive devices such as leg or neck braces, canes, walkers, and wheelchairs may be required for affected individuals to navigate safely. Motor disabilities can become severe by the fifth or sixth decade of life. Many patients may experience problems with speech or swallowing, in part due to issues with face, jaw and esophageal muscles. Muscle pain can also become a persistent issue.
Non-muscular issues are common in many systems (e.g. cardiac, respiratory, GI and endocrine systems), although most people will not experience symptoms in all of these areas. Symptoms may include cataracts, insulin resistance, excessive daytime sleepiness, and declining cognitive function. Chest infections are common and may trigger respiratory failure. Serious cardiac problems can also occur. Such respiratory and heart issues are the main causes of mortality in individuals with this form of myotonic dystrophy.
Although no disease-altering therapies exist, early diagnosis and symptomatic treatment greatly improve the quality of life for individuals affected with this disorder. Regular monitoring of systems can identify potentially life-threatening conditions and allow patients to avoid or reduce complications seen as the disease progresses.
More technical information on the symptoms, diagnosis and management of Adult-Onset Myotonic Dystrophy: DM1 can be found by clicking here.