Duchenne muscular dystrophy (DMD) is a progressive genetic disorder that gradually weakens the body’s muscles.
It is the most common muscle pathology of childhood. 1 in 3,300 live born males in all races live with Duchenne. It is caused by a mutation of a gene on the X chromosome, which provides the instruction for the production of the protein Dystrophin. This protein is located inside the muscle cell membrane. When it is absent, the muscle cells collapse and die and Duchenne muscular dystrophy develops.
What causes DMD?
Within our gene makeup, there is an important muscle protein called dystrophin, which is one of the largest genes found to date. Dystrophin acts as the glue that holds muscles together. Without dystrophin, muscles are not able to operate properly and will eventually suffer progressive damage.
Each gene codes for a specific and unique protein. These proteins build the body, and keep it running smoothly. There are thought to be roughly 100,000 genes in each human, and as many proteins. Dystrophin is only one of them. In DMD, the gene that codes for dystrophin mutates and the body is unable to produce this protein.
Dystrophin’s main function is to serve as a “connector” in the cell’s structural support system. When dystrophin is faulty, two things happen. First, muscles cannot contract normally, which leads to weakness. Second, as a muscle cell contracts, its delicate membrane tears, spilling the contents of the cell into the surrounding fluid.
Not only do vital substances leak out of muscle fibers, but harmful substances pour in. As with any injury to the body, immune cells arrive to remove the damaged cells. The injured muscle cells are “cleared away” and are replaced with hard, fibrous or rubbery scar tissue.
What are the symptoms?
Symptoms of DMD usually appear between ages two and five years and may include difficulty: running, jumping, climbing and rising from the floor; frequent falls, enlarged calf muscles, toe walking and delays in language acquisition. The first muscles affected are those around the hips and upper thigh. Weakness gradually progresses to include all skeletal muscles, the muscles of respiration and the heart. Most kids with DMD are confined to a wheelchair by the age of 12. The symptoms progress as follows:
- Tightening of joints and tendons is another symptom boys with DMD may suffer from. This is called contracture. It typically affects the ankles first, followed by the hips and knees, and finally, the joints of the upper limbs. Physical therapy is used to help offset this.
- Scoliosis is a curvature of the spine. If severe, scoliosis can be disfiguring and eventually limit the function of the lungs and upper limbs. Young men who have DMD often require surgery to help straighten their spines. In this major operation, doctors insert a metal rod to keep the spine straight.
- Speech, behavioral, and cognitive deficits are more common in boys who have DMD due to dystrophin abnormalities in the brain. About one third of young men with DMD have some degree of a learning disability. Unlike progressive muscle weakness, when a learning disability does occur in a boy with DMD, it does not worsens as time goes on.
- As boys with DMD grow into teenagers, respiratory muscle function may begin to decline enough to change the way lungs pull air in and push it out. As DMD progresses, the diaphragm becomes weakened and breathing becomes more difficult. At the same time, muscles responsible for coughing are also growing weaker and are not able to support the diaphragm. This may allow a simple cold to quickly progress into pneumonia in young men with DMD.
- During the teen years, young men with DMD will often develop heart problems as the muscle layer of the heart begins to deteriorate. This puts the young men at risk of a heart attack.
Scientists believe there will be a cure for DMD in your lifetime… The goal is to find a cure in time for the generation of boys who are now living with this disease…