This condition is inherited in an X-linked recessive pattern meaning that the gene associated with this condition is located on the X chromosome. Because males only have one X chromosome, one altered copy of the gene is enough to cause the condition. Females, on the other hand, have two X chromosomes, making it unlikely that they will have two altered copies of the gene in order to inherit the condition. So remember, males are much more likely to inherit this disorder. The defect affects dystrophin, a protein involved in anchoring skeletal muscle cells to the basement membrane.
Skeletal muscles become progressively weaker. This weakness may result in chronic limb contractures due to limited use.
Children present with early motor problems, including a delay in walking, running, and climbing stairs.
This is a classic maneuver that children with muscular dystrophy employ in order to stand up. Due to lower limb muscle weakness, a child will align the torso parallel to the ground with hands and knees on the ground. Then, the child pushes up with their arms, essentially walking their hands backwards toward the lower limbs. The hands then push off the lower limbs, and the lower back muscles contract in order to erect the torso. These children often present with lordosis due to excessive use and bearing of weight of the lumbar region of the back.
Pseudohypertrophy of the calves is common in this disease. The pseudohypertrophy seen in this disease is due to fatty and connective tissue deposits replacing the muscle of the calves.
Weakness in the gluteus medius and maximus muscles in the legs and buttocks causes an inability to stabilize the pelvis when walking. These patients present with a classic waddle walk or gait.
In Duchenne muscular dystrophy, the child often loses the ability to ambulate on their own by age 12. These children become wheelchair-dependent and then bedridden. Suspect Becker Dystrophy if the child is still ambulating independently past 13 years of age.
The disease progresses to affect the heart and respiratory muscles (e.g., the diaphragm). The patient may ultimately require respiratory support as they lose the muscle strength to breathe on their own.
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