What is Duchenne- and Becker muscular dystrophy?
Duchenne and Becker MD are both X-linked recessive disorders. Both conditions are caused by mutations in the dystrophin gene, which encodes the protein dystrophin. A certain part of the DNA is missing, doubled, or changed so the code cannot be read properly by the body. Males have only one copy of the X chromosome from their mother and one copy of the Y chromosome from their father, that is why mainly man/boys are affected. A woman who has a genetic change in one of her two copies is said to be ‘a carrier’ of Duchenne muscular dystrophy. However, Duchenne and Becker can occur when the gene mutates spontaneously.
Difference between Duchenne and Becker
Where Duchenne patients have a complete lack of the gene that produces dystrophin, Becker patients have lower levels or a shorter version of this muscle-protecting protein. Duchenne symptoms start to show when patients are babies or children. People with Becker have less severe symptoms that will often only show later in life when they become adults. This is why Becker can be seen as a milder form of Duchenne. However, some patients are already showing symptoms at a younger age.
Average age of diagnosis
In most countries, the average age of diagnosis of DMD is above 4 years of age and the diagnostic delay around 2.5 years. Parents see symptoms much earlier and some symptoms are already visible when the children are very young. Lack of awareness of DMD in (first line) health care professionals seeing these children is a major factor that contributes to this delay.
With the current standards of care, people with Duchenne can live into their early 30s and beyond. However, still a certain percentage of boys with DMD die in their late teens, mainly due to cardiac complications. The average life expectancy of Becker patients is somewhere between 40 and 50 years. However, with clinical care continuing to improve, as well as clinical trials, research and new therapies, the quality and quantity of life with Duchenne and Becker are enhanced each year.
Depending on a lot of factors including the type of mutation, Duchenne and Becker are different for every person. Even a sibling, having the same mutation, can have a different progression. The different stages in which Duchenne and Becker people are divided are based on whether patients are able to walk (ambulant) or not (early loss of ambulation, late loss of ambulation).