How Fabry disease is inherited
Fabry disease is an inherited disorder, with the genetic alteration (called a mutation) being found on the X chromosome (see genetic characteristics).
DNA, the building block of cells, is made up of 23 pairs of chromosomes. The chromosome pair that determines our gender contains either two X chromosomes for a female or an X and a Y chromosome for a male. Daughters (XX) inherit an X chromosome from their mother and an X chromosome from their father. Therefore, all daughters of an affected man will inherit one altered X chromosome from their father and one normal X chromosome from their mother. The presence of one normal and one altered X chromosome means that symptoms of Fabry disease may not appear, or if they do, it will usually be later than in males. The symptoms of Fabry disease may also be less severe, which means females may be more difficult to identify. All of the sons of an affected man will inherit the Y chromosome from their father and the X chromosome from their mother and so will not be affected.
This was once thought a typical ‘X linked recessive condition’ and in theory this is the case, but there are examples whereby a ‘spontaneous mutation’ has occurred meaning there has been no heriditary pattern within that particular family. There is significant research and data to show that women who were always classed as ‘carriers’ therefore not having the disease can be significantly affected and have symptoms as severe as males with Fabry disease.
Example of the inheritance of Fabry disease from an affected male.
In the situation where it is the mother who has Fabry disease, there is a 50% chance that each child born will also have Fabry disease. If boys inherit the altered X chromosome from their mother, they will develop symptoms, but if they inherit the normal X chromosome from their mother, they will not. If girls inherit the altered X chromosome then they may or may not show symptoms of Fabry disease.
Example of the inheritance of Fabry disease from an affected female.