The average age at diagnosis of BMD was 11 years, but the range is very wide – sometimes the diagnosis can be made in early childhood or in adulthood. Symptoms usually begin in childhood very lightly. often cramps on exercise are the only problem at first, but some boys are affected late in learning to walk. Most people with BMD are not very athletic in childhood, and many are struggling with school sports. Later, in adolescence or twenty years, muscle weakness becomes more apparent causing difficulty in walking fast, running and climbing stairs. Still later it may be difficult to lift heavy objects above waist level.
Men with Becker MD can typically become unable to walk in their forties or 50 years or even later but there are alternatives less frequent and more rapidly progressive Becker dystrophy in which this can occur in their twenties or thirties. Over a period of several years, some muscles become weak and waste, including some shoulder muscles, arms and thighs, while others who are less poor are often extended – usually particularly visible in the muscles of calf.
The muscles of facial expression, speech and swallowing and involuntary muscles (such as those of the bowel and bladder) are not affected in Becker MD. It is important to be aware that some people with BMD can have problems with their heart and long-term respiratory muscles. Often these do not cause symptoms and look at these problems, which can often be treated, is an important reason to stay in touch with a specialist clinic.