Duchenne Muscular Dystrophy (DMD) is a X-linked disorder caused by mutation in the dystrophin gene, which codes for the protein dystrophin. Phenotypical presentation of DMD is almost exclusive to males. Symptoms usually appear prior to the age of 6 in boys. At first, he may not be able to stand well & his calf muscles may become enlarged. Eventually, he will need leg braces and then a wheelchair. Cognitively, the brain usually remain intact. The average life expectancy is around 25 years.