What is Duchenne muscular dystrophy?
Duchenne muscular dystrophy (DMD) is a genetic condition which causes progressive muscle degeneration and weakness. DMD is caused by mutations in the Dystrophin gene, and is one of four diseases known as the dystrophinopathies. The condition usually only affects males, and symptoms are usually observed in early childhood – typically between the ages of 2 and 3.
What causes Duchenne muscular dystrophy?
DMD is caused by a mutation in the gene called Dystrophin located on the X-chromosome. The mutation prevents the production of dystrophin protein, and its absence results in progressive muscle weakness as muscle cells break down and are gradually lost.
DMD is a genetic condition which can be inherited from the mother or be caused by a spontaneous mutation in a child’s genes (de novo mutation). As the dystrophin gene is on the X-chromosome, DMD almost only affects males (females have two X-chromosomes and the second copy can compensate for the faulty one). Females with one affected gene (called carriers) can pass the mutated gene to their children; Females with one affected gene (called carriers) can pass the mutated gene to their children; female carriers are at risk of developing heart problems and, therefore, should be monitored by a cardiologist.
What are the signs and symptoms of Duchenne muscular dystrophy?
The first signs and symptoms of DMD usually occur in early childhood: growth rate is typically slower than normal and those with DMD are usually late walkers. In toddlers, enlarged calf muscles may be evident due to abnormalities in muscle tissue.
Young children may have difficulty running, climbing stairs, and getting up from the floor to an upright position. When walking, affected boys may display a waddling gait and walk on their toes or the balls of their feet. Difficulties with balance and raising upper limbs may also be a sign of muscle weakness.
A lack of dystrophin can weaken the muscles that operate the lungs and diaphragm which can lead to respiratory issues and symptoms such as shortness of breath, headaches, and difficultly concentrating or staying awake. Children who use wheelchairs tend to have poor pulmonary function.
DMD causes heart problems including cardiomyopathy and conduction abnormalities. The heart should be closely monitored by a paediatric cardiologist as problems can occur without any symptoms.
Although serious cognitive disability is not common, boys with DMD may have some degree of learning disability affecting attention focusing, verbal learning and memory and/or emotional interaction. If a child is diagnosed with a learning disability, educational and psychological intervention can be put in place to support boys and their families.
How does the disease progress?
It is common for boys diagnosed with DMD to begin using a wheelchair by the age of 11. At first a wheelchair may only be used for long distances, however, later it is likely that affected boys will need to use a wheelchair full time.
As the disease progresses, muscle weakness means that maintaining a good posture is increasingly difficult, therefore, complications are more likely. DMD is a severe disease that shortens life expectancy, however, the high standards of care now available for patients means that many young men with DMD reach adulthood.