What is Becker muscular dystrophy?

Becker muscular dystrophy (BMD) is a genetic condition that causes a weakness in the muscles that progresses over time leading to increasing disability. Caused by a mutation in the dystrophin gene, it is a disease closely related to Duchenne muscular dystrophy, although it is less common. The progression and severity of the disease can vary significantly from person to person.

What causes Becker muscular dystrophy?

BMD is a genetic condition where a mutation occurs in the dystrophin gene located on the X-chromosome. The genetic mutation results means less dystrophin protein is produced and/or the dystrophin protein is smaller, and only partially functional. Dystrophin is vital in maintaining the integrity of muscles, and these changes mean muscle fibres break down and muscles gradually weaken. As the dystrophin gene is on the X-chromosome, BMD almost only affects males (females have two X-chromosomes and so one can compensate for the faulty one). While females who have one affected gene usually won’t show symptoms, they can be carriers of the disease and, therefore, the disease may be passed onto their children. The mutation can also arise spontaneously and does so in up to a third of all cases.

What are the signs and symptoms of Becker muscular dystrophy?

The symptoms of BMD can be mild initially, presenting with a delay in learning to walk, muscle cramps after exercise or generally struggling with sports. Later, those in their teens or 20s, may begin to experience more difficulty running, climbing stairs, and getting up from the floor. As muscles weaken, symptoms may manifest in the shoulders and arms and individuals may have trouble lifting objects above waist level and/or lifting their arms above shoulder level. Muscles that are weakened are often enlarged in people with BMD, this is particularly noticeable in the calf muscles.

Some people with BMD may also have heart problems (such as cardiomyopathy) and this can occur at any age. In BMD, heart problems often do not cause any symptoms and can often be treated.

How does the disease progress?

Some people with BMD will eventually require a wheelchair, this is usually between the ages of 40 to 50 (but could also happen earlier with more rapidly progressing cases). On the other hand, there are people with BMD who never lose the ability to walk and live into their 70s or 80s.