Becker muscular dystrophy is the same basic disease as Duchenne muscular dystrophy, except it is less common and the symptoms are milder and slower to progress. It also only affects males, and occurs in about 1/30,000. Symptoms often begin during adolescence. Once symptoms begin, they follow a slower, but similar, course to that of Duchenne muscular dystrophy. Patients continue to be able to walk through late teens to early adulthood. Enlarged calves (pseudohypertrophy) and the breakdown of heart muscle (cardiomyopathy) are much the same as in those with Duchenne muscular dystrophy. Learning disabilities are less common in Becker MD. Many patients die, due to complications, in their mid-to-late 20s. Less than half of those with Becker MD survive to 40 years of age. Those that do are typically severely disabled.