Muscular dystrophy

Muscular dystrophy is a rare group of more than 30 inherited muscle diseases in which the muscle fibers are extremely susceptible to damage. As the disease gets more severe over time, even just doing everyday tasks may be a struggle.

This neuromuscular disease causes the muscles, primarily voluntary muscles, to become progressively weaker. In the late stages of muscular dystrophy, fat and connective tissue often replace muscle fibers and in some types of muscular dystrophy, even the heart muscles, other involuntary muscles and other organs are affected. Although experts are still debating about the possible cause, the most common types of muscular dystrophy appear to be due to a genetic deficiency of the muscle protein which is called dystrophin.

Unfortunately, there's no cure for muscular dystrophy, but there are certain medications and therapy that can slow the course of the disease and make your life easier. These dystrophies weaken the muscles slowly and over time, so children, teens, and adults who have the disease can gradually lose the ability to do the things that they used to take for granted, like walking or even just sitting up. 

Mechanism of muscle damage

Muscles, just like any other tissue, need many different kinds of proteins to stay healthy. The ones involved with the muscular dystrophy disease are the kind that the human body actually creates naturally on its own. This process is genetically controlled because genes are telling the body how to make the proteins your muscles so desperately need. In people with MD, however, these genes carry wrong information so the body is not able to make these proteins properly.

Without these important proteins, the muscles will start to break down and weaken over time. At first those with MD may have no trouble doing daily tasks, but after a while, they may become imbossible.

Signs and symptoms of muscular dystrophy

Because there are many different types of muscular dystrophies signs and symptoms vary according to the type. However there are are three cardinal signs of MD:

• Muscle weakness
• Apparent lack of coordination
• Progressive crippling and contractures of the muscles 

Different types of muscular dystrophy

Duchenne muscular dystrophy

This form of dystrophy is the most severe form of dystrophinopathy.

Research shows that signs and symptoms of Duchenne usually appear between the ages of 2 and 5. It first affects the muscles of the pelvis, upper arms and upper legs. Unfortunately most kids with this kind of dystrophy will die by their late teens or early 20s, often from pneumonia, respiratory muscle weakness or cardiac complications.

Signs and symptoms of Duchenne may include:

• Frequent falls
• Large calf muscles
• Difficulty getting up from a lying or sitting position
• Weakness in lower leg muscles, resulting in difficulty running and jumping
• Mild mental retardation

Becker's muscular dystrophy

Becker's muscular dystrophy is a milder form of dystrophinopathy.
Signs and symptoms of Becker's MD are similar to those of Duchenne. In general, the onset of the signs and symptoms appear later.

Myotonic dystrophy - Steinert

This type of dystrophy is known as Steinert's disease. It produces stiffness of muscles and an inability to relax muscles at will. Although this form of dystrophy can affect children, it often doesn't affect people until adulthood.

Besides myotonia, signs and symptoms of adult-onset myotonic dystrophy may include:

• Weakening of voluntary muscles that control your arms and legs
• Weakening of head, neck and face muscles
• Weakening of muscles involved in breathing and swallowing
• Fainting or dizziness, which may indicate that the disease is interfering with the conduction of electrical signals that keep the heart rate normal.
• Weakening of muscles of hollow internal 
• Difficulty sleeping well at night and daytime sleepiness, and inability to concentrate 
• Frontal balding in men
• Clouding of the lenses of the eyes 
• Mild diabetes

Facioscapulohumeral muscular dystrophy

Also known as Landouzy-Dejerine disease, this form involves progressive muscle weakness, usually in this order:

• Face
• Shoulders
• Abdomen
• Feet
• Upper arms
• Pelvic area
• Lower arms

Limb-girdle muscular dystrophy

Muscles usually affected first by this form of muscular dystrophy include hips and shoulders. It then slowly progresses to the arms and legs. 

Congenital muscular dystrophy

Signs of congenital MD may include:

• General muscle weakness
• Joint deformities

Experts are saying that this form is apparent at birth and progresses slowly. More serious forms of these congenital MDs may involve severe mental and speech problems as well as seizures.

Oculopharyngeal muscular dystrophy

This type affect eyelids and throat muscles. Symptoms include

• drooping of the eyelids
• weakness of the muscles of the eye, face and throat
• difficulty swallowing

Distal muscular dystrophy

This type of dystrophy involves the muscles farthest away from the center of the body. These muscles include those on the hands, forearms, feet and lower legs. This form of dystrophy generally begins in adulthood between the ages of 40 and 60.

Emery-Dreifuss muscular dystrophy - EDMD

This form of muscular dystrophy usually begins in the muscles of the:

• Shoulders
• Upper arms
• Shins

EDMD is another form of muscular dystrophy that mostly affects boys. It involves muscles in the shoulders, upper arms, and shins, and it often causes joint problems (joints can become tighter in people with EDMD). The heart muscle may also be affected.

Screening and diagnosis

A simple but careful review of family's history of muscle disease can help doctor reach a diagnosis. 

Blood tests
Damaged muscles release enzymes such as creatine kinase (CK) into the blood. High blood levels of this enzyme suggest a muscle disease such as muscular dystrophy.

Electromyography
Electromyography is performed using a thin-needle electrode which is being inserted through skin into the muscle to be tested. These electrodes measure electrical activity while the patient is gently tightening and relaxing the muscle. Changes in the pattern of electrical activity can confirm a muscle disease. 

Ultrasonography
Ultrasonography represents one of the newest diagnostic methods. It involves high-frequency sound waves which are used to produce precise images of tissues and structures within body. This method represents a noninvasive way of detecting certain muscle abnormalities, even in the early stages of the disease.

Muscle biopsy
Muscle biopsy is also a very good diagnostic tool. A small piece of muscle is taken for laboratory analysis.

Genetic testing
As we mentioned before, blood samples are examined for mutations in the gene that produces dystrophin. These tests examine the portions of the dystrophin gene responsible for most cases of Duchenne and Becker's muscular dystrophies. They also identify deletions or duplications on the dystrophin gene in about two-thirds of people with Duchenne and Becker's MDs.