Distal Muscular Dystrophy
What is Distal Muscular Dystrophy?
Distal MD is the rarest type of muscular dystrophy. This form of MD is actually a group of autosomal-dominant inherited diseases that have in common their weakening effects on the distal muscles. The distal muscles are those of the extremities, (distal meaning farthest from the center) and include muscles in the hands, forearms, lower legs and feet. The onset of Distal MD is generally between the ages of 40 and 60, and the primary symptom is weakness in the hands and other affected muscles.
Although its course can be variable, Distal MD is generally slower in progression than other dystrophies. It is also generally less severe and affects fewer muscles than other dystrophies.
After carefully evaluating a patient’s medical history, the doctor will perform a thorough physical exam to rule out other causes. If MD is suspected, there are a variety of laboratory tests that can be used to solidify a diagnosis. These tests may include:
Blood tests: When blood tests are performed to test for MD, the doctors are looking for an enzyme called creatine kinase (CK). This enzyme rises in the blood due to muscle damage or deterioration and may reveal some forms of MD before any physical symptoms appear.
Muscle biopsy: During a muscle biopsy, a small piece of muscle tissue is removed and then examined under a microscope. If MD is present, changes in the structure of muscle cells and other characteristics of the different forms of MD can be detected. The sample can also be stained to detect the presence or absence of particular proteins.
Electromyogram (EMG): An EMG is a test that measures the muscle’s response to stimulation of its nerve supply (nerve conduction study) and the electrical activity in the muscle (needle electrode examination). Both components of the EMG are very useful in diagnosing MD.
Genetic tests: Several of the muscular dystrophies can be positively diagnosed by testing for the mutated gene involved. These include Duchenne, Becker, Distal and some forms of Limb-girdle and Emery-Dreifuss dystrophies.
There is no cure for muscular dystrophy, although some drugs still in the trial stage have shown promise in slowing or delaying the progression of the disease. For the time being, treatment is aimed at preventing complications due to the effects of weakness, decreased mobility, contractures, scoliosis, heart defects and respiratory weakness.
Physical therapy: Physical therapy, especially regular stretching, is important in helping to maintain the range of motion for affected muscles and to prevent or delay contractures. Strengthening other muscles to compensate for weakness in affected muscles may be of benefit also, especially in earlier stages of milder MD. Regular exercise is important in maintaining good, overall health, but strenuous exercise may damage muscles further. For patients whose leg muscles are affected, braces may help lengthen the period of time that they can walk independently.
Surgery: If a patient’s contractures have become more pronounced, surgery may be used to relieve the tension by cutting the tendon of the affected muscle then bracing it in a normal resting position while it regrows. Other surgeries are used compensate for shoulder weakness in facioscapulohumeral MD (FSH MD), and to keep the breathing airway open for people with distal MD who sometimes experience sleep apnea. Surgery for scoliosis is often needed for patients with Duchenne MD.
Occupational therapy: Occupational therapy involves employing methods and tools to compensate for a patient’s loss of strength and mobility. This may include modifications at home, dressing aids, wheelchair accessories and communication aids.
Nutrition: Nutrition has not been shown to treat any conditions of MD, but it is essential to maintaining good health.
Cardiac care: Arrhythmias are often a symptom with Emery-Dreifuss and Becker MD and may need to be treated with special drugs. Pacemakers may also be needed in some cases and heart transplants are becoming more common for men with Becker MD.
Respiratory care: When the muscles of the diaphragm and other respiratory muscles become too weak to function on their own, a patient may require a ventilator to continue breathing deeply enough. Air may also be administered through a tube or mouthpiece. It is therefore very important to maintain healthy lungs to reduce the risk of respiratory complications.
Like many other disorders, understanding and education about muscular dystrophy is the most important tool with which to manage and prevent complications. The following organizations can provide more information about muscular dystrophy:
Progression: Distal muscular dystrophy is slowly progressive, and not life-threatening.
- OMIM Link