Muscular Dystrophy Health Article

Facioscapulohumeral muscular dystrophy

FSH varies in its severity and age of onset, even among members of the same family. Symptoms most commonly begin in the teens or early twenties, though infant or childhood onset is possible. Symptoms tend to be more severe in those with earlier onset. The condition is named for the regions of the body most severely affected by the condition: muscles of the face (facio-), shoulders (scapulo-), and upper arms (humeral). Hips and legs may be affected as well. More than half of children with FSH may develop partial or complete sensorineural deafness.

The first symptom noticed is often difficulty lifting objects above the shoulders. The weakness may be greater on one side than the other. Shoulder weakness also causes the shoulder blades to jut backward, called scapular winging. Muscles in the upper arm often lose bulk sooner than those of the forearm, giving a "Popeye" appearance to the arms. Facial weakness may lead to loss of facial expression, difficulty closing the eyes completely, and inability to drink through a straw, blow up a balloon, or whistle. Persons with FSH may not be able to wrinkle their foreheads. Contracture of the calf muscles may cause foot-drop, leading to frequent tripping over curbs or rough spots. People with earlier onset often require a wheelchair for mobility, while those with later onset rarely do.

Myotonic dystrophy

Symptoms of myotonic dystrophy include facial weakness and a slack jaw, drooping eyelids (ptosis), and muscle wasting in the forearms and calves. Persons with myotonic dystrophy have difficulty relaxing their grasp, especially if the object is cold. Myotonic dystrophy affects heart muscle, causing arrhythmias and heart block, and the muscles of the digestive system, leading to motility disorders and constipation. Other body systems are affected as well. Myotonic dystrophy may cause cataracts, retinal degeneration, mental deficiency, frontal balding, skin disorders, testicular atrophy, sleep apnea, and insulin resistance. An increased need or desire for sleep is common, as is diminished motivation. Severe

disability affects some people with this type of dystrophy within 20 years of onset, although most do not require a wheelchair even late in life. The condition is extremely variable. Some individuals show profound weakness as newborns (congenital myotonic dystrophy), others show mental retardation in childhood, many show characteristic facial features and muscle wasting in adulthood, while the most mildly affected individuals show only cataracts in middle age with no other symptoms.

Oculopharyngeal muscular dystrophy

OPMD usually begins in a person's thirties or forties, with weakness in the muscles controlling the eyes and throat. Symptoms include drooping eyelids, difficulty swallowing (dysphagia), and weakness progresses to other muscles of the face, neck, and occasionally the upper limbs. Swallowing difficulty may cause aspiration, or the introduction of food or saliva into the airways. Pneumonia may follow.

Distal muscular dystrophy

DD usually begins in the twenties or thirties, with weakness in the hands, forearms, and lower legs. Difficulty with fine movements such as typing or fastening buttons may be the first symptoms. From that point, symptoms slowly progress and the condition usually does not affect life span.

Congenital muscular dystrophy

CMD is marked by severe muscle weakness from birth, with infants displaying "floppiness" (very poor muscle tone). They often have trouble moving their limbs or head against gravity. Mental function is normal but some are never able to walk. They may live into young adulthood or beyond. In contrast, children with Fukuyama CMD are rarely able to walk, and have severe mental retardation. Most children with this type of CMD die in childhood.

Diagnosis

The diagnosis of muscular dystrophy involves a careful medical history and a thorough physical exam to determine the distribution of symptoms and to rule out other causes. Family history may give important clues, since all the muscular dystrophies are genetic conditions, although no family history will be evident in the event of new mutations. With autosomal recessive inheritance, a family history may also be negative for muscular dystrophy.

Lab tests may include:

• Blood level of the muscle enzyme creatine kinase (CK). CK levels rise in the blood due to muscle damage, and may be seen in some conditions even before symptoms appear.
• Muscle biopsy, in which a small piece of muscle tissue is removed for microscopic examination. Changes in the structure of muscle cells and presence of fibrous tissue or other aberrant structures are characteristic of different forms of muscular dystrophy. The muscle tissue can also be stained to detect the presence or absence of particular proteins, including dystrophin.
• Electromyogram (EMG). This electrical test is used to examine the response of the muscles to stimulation. Decreased response is seen in muscular dystrophy. Other characteristic changes are seen in muscular dystrophy.
• Genetic tests. Several of the muscular dystrophies can be positively identified by testing for the presence of the altered gene involved. Accurate genetic tests are available for DMD, BMD, DM, several forms of LGMD, and EDMD. Genetic testing for some of these conditions in future pregnancies of an affected individual or parents of an affected individual can be performed before birth through amniocentesis or chorionic villus sampling. Prenatal testing can only be undertaken after the diagnosis in an affected individual has been genetically confirmed and the couple has been counseled regarding the risks of recurrence.
• Other specific tests as necessary. For EDMD, DMD and BMD, for example, an electrocardiogram may be needed to test heart function, and hearing tests are performed for children with FSH.

For most forms of muscular dystrophy, accurate diagnosis is not difficult when performed by someone familiar with the range of conditions. There are exceptions, however. Even with a muscle biopsy, it may be difficult to distinguish between FSH and another muscle condition, polymyositis. Childhood-onset LGMD is often mistaken for the much more common DMD, especially when it occurs in boys. BMD with an early onset appears very similar to DMD, and a genetic test may be needed to accurately distinguish them. The muscular dystrophies may be confused with conditions involving the motor neurons, such as spinal muscular atrophy; conditions of the neuromuscular junction, such as myasthenia gravis; and other muscle conditions, as all involve generalized weakness of varying distribution.

Prenatal diagnosis (testing of the baby while in the womb) can be performed for those types of muscular dystrophy where the specific disease-causing gene alteration has been identified in a previously affected family member. Prenatal diagnosis can be accomplished by utilizing DNA extracted from tissue obtained by chorionic villus sampling or amniocentesis.