The following information may help to address your question:
Duchenne muscular dystrophy (DMD) is a type of dystrophinopathy, which is a group of muscle diseases caused by mutations in the DMD gene, which encodes the protein dystrophin; the other dystrophinopathies are Becker muscular dystrophy (BMD) and DMD-associated dilated cardiomyopathy (DCM). Although these disorders are caused by mutations in the same gene, they do differ with regard to age of onset, course and pace of progression, symptoms, and life expectancy. DMD and BMD primarily affect the skeletal muscles, while DCM primarily affects the heart.
Conditions that may be part of the differential diagnosis of the dystrophinopathies include: