DMD, Duchenne Muscular Dystrophy
DMD, Duchenne Muscular Dystrophy: Is the most common fatal genetic disorder diagnosed during early childhood, affecting approximately 1 out of every 3,500 boys and 20,000 babies born each year. DMD is a recessive X-linked form of muscular dystrophy,
affecting around 1 in 3,600 boys, which results in muscle degeneration and eventual death. The disorder is caused by a mutation in the dystrophin gene, located on the human X chromosome, which codes for the protein dystrophin, an important structural component within muscle tissue that provides structural stability. While both sexes can carry the mutation, females rarely exhibit signs of the disease.
Symptoms usually appear in male children before age 6 and may be visible in early infancy. Even though symptoms do not appear until early infancy, laboratory testing can identify children who carry the active mutation at birth.
Progressive proximal muscle weakness of the legs and pelvis associated with a loss of muscle mass is observed first. Eventually this weakness spreads to the arms, neck, and other areas. Early signs may include enlargement of calf and deltoid muscles, low endurance, and difficulties in standing unaided or inability to ascend staircases.
As the condition progresses, muscle tissue experiences wasting and is eventually replaced by fat and fibrotic tissue (fibrosis). By age 10, braces may be required to aid in walking but most patients are wheelchair dependent by age 12.
Later symptoms may include abnormal bone development that lead to skeletal deformities, including curvature of the spine. Due to progressive deterioration of muscle, loss of movement occurs, eventually leading to paralysis. Intellectual impairment may or may not be present but if present, does not progressively worsen as the child ages. The average life expectancy for patients afflicted with DMD is around 25.
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