In many families, it is inherited as a sex-linked (X-linked) trait and therefore only affects males and is carried by unaffected females. All the sons of an affected male will be unaffected but all his daughters will be carriers. With regard to the offspring of a woman who is a carrier, on average each of her daughters has a 50:50 chance of also being a carrier, and on average each of her sons has a 50:50 chance of being affected.
The condition can also be inherited as an autosomal dominant trait, which affects both males and females. Here the genetic risks are different. As in all autosomal dominant disorders on average each son or daughter of an affected parent has a 50:50: chance of also becoming affected. In the case of the recessive form, both parents are normal but there is a 1 in 4 chance of any future children also being affected.
To make matters even more complicated, sometimes in x-linked and dominant cases there is no family history of the disorder, only one individual in the family being affected. In these cases the disease has arisen as the result of a new mutation in the affected individual but who may then later transmit the disorder to his or her children.
For these various reasons it is very important to seek the professional advice of a neuromuscular specialist or medical geneticist if you are at all concerned about the risks to your children and other relatives.