OverviewMuscular dystrophy is a genetic abnormality resulting in the gradual weakening of the muscles of the body. As the weakness progresses, disability ensues. Duchenne muscular dystrophy (DMD) isthe most common and severe form of muscular dystrophy. It usually affects boys, although very rarely it also affects girls. Patients are likely to require a wheelchair at a young age and are unlikelyto survive longer than 20-30 years of life. CausesDMD is an X-linked recessive disease usually affecting boys. While this mode of inheritance makes up the majority of cases, in around 30% of casessporadic mutations may be responsible. Rarely, females can be affected with a mild form of the disease, but more often they are often silent carriers of the mutation. DMD is caused by a mutation in thedystrophin gene, which encodes for the protein dystrophin. The absence of this protein in DMD leads to muscle necrosis and ultimately replacement of muscle fiber with adipose and fibrotic tissue. The image opposite shows a light micrograph of a section through muscle tissue of a patient affected by duchenne muscular dystrophy. In this section, some of the muscle fibers, shown in dark purple,have been replaced by fibrous tissue, shown in light purple. SymptomsDMD manifests in childhood with the majority of diagnoses made between the ages of 3 and 5 years.
In boys with delayed motorskills, the possibility of muscular dystrophy being responsible should be suspected. Delayed speech or walking, toe-stepping gait and difficulty in climbing stairs are all suggestive of a diagnosis ofmuscular dystrophy.
On clinical examination, proximal muscle-wasting can be observed with pseudohypertrophy (increased in size without hypertrophy) of the calves. The child should be observed forGower’s sign, which is seen when the child attempts to stand from either the squatting or kneeling position; the child subsequently has to 'walk' his hands up his legs in order to attain a vertical...
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