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WHAT IS DUCHENNE MUSCULAR DYSTROPHY?

 

Duchenne muscular dystrophy (DMD) is one of a group of rare inherited diseases that cause the muscles to become weak.

 

• DMD only affect boys and is the most common type of muscular dystrophy; the condition is diagnosed in about one in 3000 babies. There are some rare types of muscular dystrophy that affect girls, but these tend to be forms of the disease that have much milder symptoms. 
• Muscular dystrophy arises because of a gradual deterioration in the fibres that make up muscles. 
• The condition is inherited as parents pass on an abnormal gene to their children. 
• Girls can carry and pass on the abnormal gene that is responsible for duchenne muscular dystrophy. 

Duchenne muscular dystrophy causes the muscles to weaken, making walking progressively more difficult. A wheelchair is often necessary by nine to twelve years of age.

 

Other types of muscular dystrophy

 

These are rare and have slightly different symptoms from DMD

 

Becker muscular dystrophy: this affects boys but is rarer than DMD. Although a child has the disease from birth, the symptoms may become apparent only between the ages of 11 and 15. The muscle weakness often becomes debilitating when a person is in his 40s or 50s.

 

Childhood muscular dystrophy: this condition can affect girls as well as boys, and more common if parents are blood relatives.

 

Limb-girdle muscular dystrophy: this type of muscular dystrophy is also seen in both girls and

boys, but it affects different muscles in the body.

 

Emery-Dreifuss muscular dystrophy: this has similar symptoms to the other types, but may also affect the heart.

 

Initial signs and symptoms

 

In DMD, the symptoms usually become apparent at around 18 months when the child fails to start walking. Parents may then notice signs that indicate that the child is having difficulty moving around.

 

The first clue that something is wrong may be that the child fails to meet milestones and is not starting to walk at the normal age.  

If a child is walking, he may 'waddle' and fall over a lot more than is normal for a toddler. 

A characteristic sign of DMD is obvious when a child is getting up to a standing position from sitting on the floor. He will 'walk' his hands up his legs to achieve a standing position (doctors call this Gower's sign). 

The muscles in the calf at the back of the leg may appear firm and slightly larger than normal, although they are in fact weak and don't function properly. Muscles in the back, legs and pelvic area are also weak. 

Children with DMD often have difficulty reaching developmental milestones. A child with DMD may have difficulty in learning to walk, and may 'waddle' and fall over more than he should.

 

How DMD is diagnosed

 

A doctor may suspect that a child has muscular dystrophy from his symptoms. He may then refer the child to a specialist pediatrician.

 

Blood tests: an enzyme called. creatine phosphokinase is normally present in healthy muscle. In muscular dystrophy it is present in very high levels.

 

Muscle tests: electromyography (EMG) is a test that measures the electrical activity in muscles. In a child with muscular dystrophy the results are abnormal. 

 

Biopsy:  this involves examining a tiny piece of muscle tissue under a microscope. Usually, dystrophin will be seen around the muscle fibres. In DMD, there is a jack or complete absence of dystrophin. This test is usually carried out under a light general anaesthetic in babies.

 

Doctors may wish to carry out tests on the heart to check whether it has been damaged.

 

If a specialist suspects that a child has DMD, he may carry out a blood test to ascertain if the child has a higher level of the enzyme creatine phosphokinase in his blood.

 

How DMD is inherited

DMD is inherited via a faulty gene on the X chromosome

 

In almost every cell in the human body is a nucleus that contains 46 chromosomes. Within each chromosome there are thousands of genes. Chromosomes and genes are made from a substance called DNA, which passes on characteristics from generation to generation.

 

• Each gene contains a 'blue print' for the manufacture of a particular protein. Proteins are the basic building-blocks of the body. 
• DMD is the result of a faulty gene on the X chromosome, which is present in both males and females. This gene is responsible for producing the protein dystrophin, which forms healthy muscle. 
• Girls can inherit the faulty gene, but do not usually develop the condition as they have two X chromosomes, one of which has a 'normal' chromosome that compensates for the abnormal chromosome. 
• Research indicates that, in boys, the faulty gene may be the result of a change in the gene after birth, and is not necessarily inherited. 

Later symptoms

 

As DMD progresses, the symptoms often become more severe, as the muscles become less and less able to provide normal movement.

 

The muscles in the arms can make picking up or holding objects firmly difficult. 

Contractures develop in the muscles in the limbs and the joints become stiff. This most commonly affects the ankles, hips and knees, which often become deformed. 

The muscles that hold the spine erect start to waste, causing it to curve (scoliosis).

Walking tends to progressively become more difficult. 

Some children have learning difficulties and find it increasingly difficult to keep up at school. 

WHAT CAN BE DONE TO HELP

 

There is currently no cure for DMD. Treatment involves assessing a child's ability and helping him to get the most out of life.

 

• Physiotherapy is vital to help a child move around and remain active, keeping limbs supple and preventing muscle wastage. Splints can be applied to limbs to prevent contractures developing, and limb exercises help to keep joints flexible and muscles strong. 
• Walking aids can be beneficial to a child who is walking but is not stable. 
• Occasionally, a child with muscular dystrophy has learning difficulties and may need specialist educational input. 
• It is important to remember that the siblings of children with DMD may sometimes feel neglected and also need some attention. 

For  More  Information:  Please  consult  your  physician  on  your  next  visit.