Duchenne muscular dystrophy is a genetic disorder which is diagnosed by the inability to produce the muscular protein dystrophin. The dystrophin gene is located on the X-chromosome. Males have only one X-chromosome, making them more susceptible to dystrophin damage, as they lack a second X-chromosome to make up for the damaged gene. A female may have the damaged gene but show no symptoms of disease because her other X-chromosome is dominant. These females are termed 'carriers'. The diagram on the right illustrates the percentage chance of giving birth to a son who suffers from DMD when the mother is a carrier of the gene. Dystrophin is an important muscle protein that acts as structural support, holding muscles together by maintaining the structural integrity of muscle cells. |  Figure 4: Inheritance pattern of recessive X-linked DMD
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Dystrophin's functions are also believed to include signalling between the inside and outside of muscle fibers. Without dystrophin, muscles fail to operate properly. This leads to progressive damage.
Duchenne is usually passed from parent to child during conception, however, random spontaneous genetic mutations can also occur during any pregnancy. This means a child can be born with DMD despite no previous family history existing. One in three cases of DMD occurs in this fashion.
