What is DMD?

Duchenne Muscular Dystrophy (DMD) is a rare, progressive, muscle-wasting disease in which those diagnosed are unable to produce dystrophin, a protein essential for the repair and stability of muscle fibers. Without dystrophin, muscle cells are damaged and replaced with connective tissue. DMD is the most common and leading fatal genetic disorder in children, affecting approximately 1 in 5,000 male births with an estimated 300,000 sufferers worldwide today. Currently, there is no cure; DMD is 100% fatal.

DMD is found primarily in boys. The dystrophin gene, which regulates dystrophin production, is located on the X-chromosome. Males, who each have one X- and Y-chromosome, are at risk for X-chromosome related disorders. Duchenne may be unknowingly passed from mother to child. Women can be carriers, but not manifest any symptoms likely due to their second, compensating X-chromosome. In approximately 35% of cases, however, DMD occurs because of a random, spontaneous mutation at formation of the dystrophin gene during pregnancy. Therefore, any child is at risk for having DMD.

DMD is generally diagnosed between the ages of 3-5 when boys start showing muscle weakness and delayed development. It is then that parents or caregivers notice some early signs of DMD such as speech delay, enlarged calf muscles, and challenges with physical tasks such as running, stair-climbing, riding a bike, and balance. Nearly 30% of the time, boys with DMD also have neurological disorders such as autism, ADHD, and other behavior or learning disabilities that make it difficult for them socially and emotionally in school. This stems from the fact that a small amount of dystrophin is located in the brain.

As the disease progresses, boys living with DMD typically lose the ability to walk between the ages of 8-12. Physical activity can be greatly limited throughout childhood. Parents and caregivers may choose to avoid some physical activity during early stage in order to preserve good muscle fiber for as long as possible. In addition to skeletal muscle strength and function, care for DMD includes a focus on heart and lung preservation. Young men living with Duchenne typically lose their lives in their mid-20’s from heart or lung failure, although it is important to note that progression can vary greatly.

The journey with Duchenne, however, doesn’t have to be like this. Thanks to the hard work and dedication of doctors, scientists, and parent organizations like Little Hercules Foundation, more clinical trials and potential treatment options exist today than ever before. Little Hercules Foundation was founded with the hope to be able to re-write ‘What is DMD’ for this generation of DMD patients and all those in the future. Click here to learn more about current research and development.


DMD Statistics


Dystrophin Gene

DNA is found in every cell in our body.  Think of it as a home owner’s manual for your body, whose content is the genetic information that make us who we are.  Our body works to read the instructions each day by flipping through all the chapters in the manual, or sections of the DNA known as genes.  Within each gene are exons that fit together in a sequential order to produce one set of instructions for that particular gene.  The mRNA delivers these instructions to another part of the cell so that it makes necessary proteins and amino acids for the body to function properly.

Duchenne muscular dystrophy is caused by an imperfection in the exons of the dystrophin gene.  The dystrophin gene (shown below) is comprised of 79 exons that are each shaped differently and fit together like a puzzle.  It is the largest known gene in the human body.  A genetic mutation in one or more of these exons can interrupt the mRNA’s ability to read the dystrophin gene’s instructions.  With altered instructions, the gene produces little to no dystrophin for the body. 

The most common DMD mutation is a deletion of one or more exons.  The missing pieces disable the existing exons from fitting together properly.  Mutations can also include duplications, where there are two or more of the same exon, or stop codon, where small alterations exist on an exon making it imperfect. 

Knowing the specific mutation is crucial to identifying whether existing therapies or potential therapies still in clinical development may help.

Refer to the links under General Duchenne Resources on our Resources page to learn more about genetic mutations, resources for testing, or how different mutations coordinate with the therapeutic pipeline.

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