Morris syndrome is caused by a genetic mutation in the AR (androgen receptor) gene located on the X chromosome. It is a genetic disease linked to the X chromosome. Its inheritance is recessive in the case of women (46,XX), so these women can be carriers. However, in the case of the male sex (46,XY), the disease manifests itself giving rise to Morris syndrome.
Affected girls can inherit their mother's altered X chromosome if she is a carrier. The AR gene mutation may also appear de novo in the egg before fertilization or in the embryo during the early stages of development.