EDMD has several forms. All of them are caused by changes (mutations) in one of three genes that each make a protein in muscle cells. These proteins are part of the envelope (membrane) around the nucleus in muscle cells. The nucleus is the sac within cells that contains the genes. A mutation in any one of these proteins can cause EDMD.
Parents can pass EDMD down to their children in different ways:
X-linked chromosome
The most common form of EDMD is X-linked. This means that the changed gene is on the X chromosome. Chromosomes contain genes and are in the nucleus of your cells. Only boys get this form of EDMD. Girls have two X chromosomes, one from each parent. Boys get one X chromosome from their mother and a Y chromosome from their father. Because a boy has only one copy of the changed gene, a mutation means that he will not have enough of the protein to keep his muscles working well. A girl with the gene defect usually gets enough normal protein from her other X chromosome. But she will be a carrier for the mutation and can pass it on to her children.
Autosomal dominant
Another form of EDMD affects both boys and girls, and either parent can pass this form down to their children. The term for this kind of inherited pattern is autosomal dominant. In this case, a parent with the disease has a 1 in 2 chance of passing it on to each of their children.
Autosomal recessive
A rare form of EDMD happens when a child inherits a mutated gene from both parents ( autosomal recessive). Both boys and girls may have this form.
All three forms of EDMD have similar symptoms. Researchers are still trying to understand the connections between these defective proteins and the muscle weakness in EDMD.