Is MECP2 duplication syndrome inherited ?
MECP2 duplication syndrome is inherited in an X-linked pattern. The gene associated with this condition is located on the X chromosome, which is one of the two sex chromosomes. In males (who have only one X chromosome), a duplication of the only copy of the MECP2 gene in each cell is sufficient to cause the condition. In females (who have two X chromosomes), a duplication of one of the two copies of the gene typically does not cause the disorder. Females usually do not have signs and symptoms of MECP2 duplication syndrome because the X chromosome that contains the duplication may be turned off (inactive) due to a process called X-inactivation.  Early in embryonic development in females, one of the two X chromosomes is permanently inactivated in somatic cells (cells other than egg and sperm cells). X-inactivation ensures that females, like males, have only one active copy of the X chromosome in each body cell. Usually X-inactivation occurs randomly, such that each X chromosome is active in about half of the body cells. Sometimes X-inactivation is not random, and one X chromosome is active in more than half of cells. When X-inactivation does not occur randomly, it is called skewed X-inactivation.  Research shows that females with an MECP2 gene duplication have skewed X-inactivation, which results in the inactivation of the X chromosome containing the duplication in most cells of the body. This skewed X inactivation ensures that only the chromosome with the normal MECP2 gene is expressed. This skewed X-inactivation is why females with an MECP2 gene duplication typically do not have any features related to the additional genetic material.