can either be inherited or occur spontaneously during germline transmission, causing to a large reduction or absence of dystrophin, a protein that provides structural integrity in muscle cells. Dystrophin is responsible for connecting the actin cytoskeleton of each muscle fiber to the underlying basal lamina (extracellular matrix), through a protein complex containing many subunits. The absence of dystrophin permits excess calcium to penetrate the sarcolemma (the cell membrane). Alterations in calcium and signalling pathways cause water to enter into the mitochondria, which then burst. In skeletal muscle dystrophy, mitochondrial dysfunction gives rise to an amplification of stress-induced cytosolic calcium signals and an amplification of stress-induced reactive-oxygen species production. In a complex cascading process that involves several pathways and is not clearly understood, increased oxidative stress within the cell damages the sarcolemma and eventually results in the death of the cell. Muscle fibers undergo necrosis and are ultimately replaced with adipose and connective tissue. DMD is inherited in an X-linked recessive pattern. Females typically are carriers of the genetic trait while males are affected. A female carrier will be unaware she carries a mutation until she has an affected son. The son of a carrier mother has a 50% chance of inheriting the defective gene from his mother. The daughter of a carrier mother has a 50% chance of being a carrier and a 50% chance of having two normal copies of the gene. In all cases, an unaffected father either passes a normal Y to his son or a normal X to his daughter. Female carriers of an X-linked recessive condition, such as DMD, can show symptoms depending on their pattern of X-inactivation. DMD is extremely rare in females (about 1 in 50,000,000 female births). It can occur in females with an affected father and a carrier mother, in those who are missing an X chromosome, or those who have an inactivated X chromosome (the most common of the rare reasons). The daughter of a carrier mother and an affected father will be affected or a carrier with equal probability, as she will always inherit the affected X-chromosome from her father and has a 50% chance of also inheriting the affected X-chromosome from her mother. Disruption of the blood–brain barrier has been seen to be a noted feature in the development of DMD. Diagnosis Genetic counseling is advised for people with a family history of the disorder. DMD can be