Duchenne muscular dystrophy is a different inherited degenerative muscle disease. It predominantly affects males, as the gene involved is located on the X chromosome. If a mother is a carrier, she has a normally functioning copy of the dystrophin gene on one of her X chromosomes and a faulty copy on her second X chromosome. She passes on only one of these genes to her offspring each time, and there is thus a ½ or 50% chance of the male children of a carrier being affected. Females have a ½ or 50% chance of being carriers, as they also inherit a normal gene from their fathers.
Female carriers generally do not have features of DMD, although occasionally they can develop mild to moderate muscle weakness. Female carriers of DMD are also at increased risk of developing a cardiomyopathy, irrespective of whether they have muscle weakness. Thus a baseline cardiac evaluation by a cardiac specialist is recommended, including clinical evaluation, ECG and echocardiography. This should be repeated every five years.