Symptoms usually begin very mildly in childhood. Cramps during exercise are often the only problem at first, but in some cases, boys may be late in learning to walk. Most people with Becker muscular dystrophy are not very athletic in childhood, and many struggle with school sport. Later, in their teens or 20s, some may find muscle weakness becoming more evident and causing difficulty in running, climbing stairs and getting up from the floor.
As muscle weakness progresses over time, it may involve the shoulders and arms, leading initially to difficulties in lifting heavy objects above waist level and then lifting the arms above shoulder level.
Over a period of many years, some muscles may become weak and wasted, especially certain muscles of the shoulders, upper arms and thighs. Other muscles that are less weak are often enlarged, and this is particularly noticeable in the calf muscles.
Typically, men with Becker muscular dystrophy may – in their 40s, 50s, or even later – become unable to walk, and require a wheelchair. In less frequent and more rapidly progressing cases of Becker muscular dystrophy, this may happen to men in their 20s or 30s.
It is important to be aware that some people with Becker muscular dystrophy may also have heart problems (cardiomyopathy), which can occur at any age. People might still be very mobile but have heart problems requiring treatment, or, as mentioned earlier, the heart problems might be the first sign of Becker muscular dystrophy.
Heart problems in Becker muscular dystrophy often do not cause any symptoms, but they can often be treated. It is therefore important for people with Becker muscular dystrophy to have regular heart monitoring by a specialist. Early treatment of heart problems (with drugs called ACE inhibitors and/or beta-blockers) can protect the heart muscle.
People with Becker muscular dystrophy can also have problems with breathing. This is more likely to be the case, however, in people who are wheelchair users and in later stages of the condition.
The muscles of facial expression, speech and swallowing, and the involuntary muscles (for example those of the bowel and the bladder) are not affected in Becker muscular dystrophy.
People with Becker muscular dystrophy have a higher risk of complications during general anaesthesia. This can be because of their heart and breathing problems, or because of a reaction to some general anaesthetics. It is important, therefore, that people with Becker muscular dystrophy inform doctors of their condition if a general anaesthetic is required.
Some people with Becker muscular dystrophy can show learning and/or behavioural difficulties. As learning difficulties are not progressive, it is important they are identified and addressed promptly (e.g. at school), to offer the child the support he will need to reach his full potential to develop his skills. Family support is essential, and specialists may need to be consulted to address specific issues of learning and behaviour.