Muscular dystrophy refers to a group of genetic diseases that prevent the muscles from developing properly. The muscle fibers are more easily damaged and do not get repaired fully, meaning the muscles weaken faster. In the skeletal muscles, this typically leads to limbs being fixed in position and to using a wheelchair; in other parts of the body, it can cause difficulties in breathing or swallowing. The most common type, Duchenne muscular dystrophy, accounts for half of all cases. Most people with Duchenne are male; about one in 3,600 boys are born with the disease. Duchenne is a hereditary disease that, due to the genetics of the condition, seldom affects girls.
Duchenne symptoms generally appear before the age of six. Boys with the condition tend to walk late, and have trouble standing up, climbing stairs, and running. Not only do these children start walking late, they gradually lose the ability to walk after developing the skill, often by the time they reach their teens. Duchenne boys usually have across-the-board motor skill deficiencies, as well as an increased risk of neurological and learning difficulties. Duchenne does not affect the ability to feel pain or other sensations, though it is generally not painful itself. The condition also affects breathing, and men with Duchenne are not expected to live much past 40—often, 30—due to respiratory difficulties.
Treatment for the forms of muscular dystrophy is the subject of ongoing research. A study involving nanoparticles to deliver a medicine called rapamycin the function of the faulty protein—as opposed to other treatment approaches that focused on the protein itself—has proven successful in experimental animals.
"The nanoparticles tend to penetrate and be retained in areas of inflammation," study author author Samuel A. Wickline, M.D., said in a statement. "Then they release the rapamycin over a period of time, so the drug itself can permeate the muscle tissue." Rapamycin cannot be administered orally because in small doses, it is ineffective in the muscles, while in large doses, it has too drastic a suppressive effect on the immune system to be safely administered. When smaller doses are targeted to muscle tissue directly, it might be possible to see an effect without compromising the patient’s safety.