Becker Muscular Dystrophy
Becker muscular dystrophy (BMD) is a more mild variant of Duchenne muscular dystrophy. The progression of Becker muscular dystrophy is similar to DMD, but the voluntary muscles retain more function than muscles do in DMD. Unfortunately, the heart muscle doesn't appear to be more mildly affected than the hearts of Duchenne muscular dystrophy patients. BMD patients tend to present with the same cardiac issues. Becker muscular dystrophy begins showing symptoms later than DMD, with the onset occurring in adolescence and late childhood. Though the disease is progressive, BMD progresses more gradually than Duchenne muscular dystrophy. It's also harder to predict the course.
Like with DMD, individuals with BMD often have enlarged calves, and the weakness occurs in the same areas first. Becker muscular dystrophy is also caused by abnormalities in dystrophin. Duchenne muscular dystrophy patients produce little to no dystrophin in their body, but individuals with BMD do synthesize dystrophin, though it's just partly functional. BMD patients have a shorter form of dystrophin, which can't provide the same function as normal dystrophin, but offers protection from the same weakness seen in DMD.