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Diagnosis of Muscular Dystrophy

A preliminary diagnosis can be performed on the basis of past symptoms and characteristic traits: different dystrophies affect different muscle groups and have a different age of onset.

Unless there is a known risk of a baby inheriting muscular dystrophy from his parents, it's usually difficult to diagnose the illness before the age of 2 or 3. Children with this condition usually have difficulties walking, getting up or climbing the stairs. They also fall down more often than their peers, and may get up off the ground by putting their hands on their knees, and then on their thighs (this is known as the Gower sign).

A doctor will first try to diagnose the illness by observing the child's gait (the way he walks) and his posture: other frequent signs are very large calf muscles and a curved back (lordosis or scoliosis)

Children affected by DMD have a characteristic way of walking (sometimes referred to as "waddling"), and they later tend to walk with their heels off the ground - putting their weight on the front of their feet

Often, in muscular dystrophy there is a loss of muscle mass (muscle wasting): in some cases this may be hard to detect visually, because muscles often are replaced by connective tissue and fat (pseudohypertrophy)

A careful diagnosis also involves careful medical history and a thorough physical exam to determine the distribution of symptoms and to rule out other causes. Family history is very important, since all the muscular dystrophies are genetic - and usually inherited - conditions (though rarely there will be new mutations which are not detectable with family history). EMG are also useful: they stimulate muscles using electrical shocks and the reaction is abnormal in individuals with muscular dystrophy. Muscle biopsies are among the most reliable tests: they consist of taking a small piece of muscle and examining it with a microscope (fibers affected by MD are unusually large and interspersed with dead cells).

The golden standard for MD diagnosis, however, is a DNA test: in the past, these tests were performed on blood samples and allowed diagnosis by identifying a specific mutation of the dystrophin gene. There is now a new DNA test, called single condition amplification/internal primer (SCAIP) sequencing, which allows doctors to have a much more accurate picture of the entire dystrophin gene, so they can find multiple variations, providing more than just one type of diagnosis. In the next years this test should become more widely available to the general public

In any case, the two most reliable tests to diagnose a muscular dystrophy are a muscle biopsy or a DNA test (even if usually a blood test is sufficient)

The usual procedure is to first look for physical signs, then use a blood test. Blood tests work by determining the level of creatine phosphokinase (CPK): in children with the condition, these levels are usually 5 to 10 times greater than the maximum level found in normal individuals, but they can get as high as 100 times

Once the blood test has revealed an abnormally high level of CPK, further analysis may be performed with a muscle biopsy or a DNA test.

Other tests may include:

  • Serum CPK
  • EMG (electromyography)
  • ECG (electrocardiography)

Muscular dystrophies can also alter the results of several tests, including:

  • Myoglobin - urine/ serum
  • LDH
  • Creatinine
  • AST
  • Aldolase

As for cardiac activity, electrocardiograms and ultrasound may be useful in determining the functionality of the child's heart.

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