RTT suspected children recommended testing process: 1, suspected children first karyotype analysis to exclude other basic chromosomal abnormalities; 2, MECP2 gene coding region sequencing; 3, if no findings, continue the above gene duplication and deletion detection; 4, still no findings, other testing means. The problem of detecting mutations in the parents of children with RTT: RTT can be inherited from both parents to the fetus, but the chances are very low. For example, gonadal chimerism in both parents; or the presence of non-random inactivation of the X chromosome in mothers with MECP2 mutations. In the case of germline chimerism, germ cells can be tested; in the case of maternal inheritance, this can be confirmed by testing the mother’s peripheral blood. Because of the low probability of all of these, specific germ cell testing is not usually required for both parents of children with RTT, and a peripheral blood mutation test is usually sufficient. The majority of RTT is a new mutation in the child and is not inherited from the parents. Therefore, parents of children with RTT should not be overly concerned about having a second child. Parents who have normal peripheral blood tests for RTT do not need to have an interventional prenatal diagnosis specifically for RTT because of the risk of miscarriage associated with interventional prenatal diagnosis; if an interventional prenatal diagnosis is needed for other reasons, the addition of a mutation locus test may help to relieve tension. Relationship between RTT and gender: Although the majority of children are female, a small number of boys are affected. The predominance of females over males is mainly related to the mechanism of the disease. Methodology of RTT genetic testing: Rett genetic testing is a research project and is done directly in our laboratory for a small cost of reagents, usually two-way sequencing and/or MLPA to ensure accuracy of results, with a reporting time of 2-3 weeks. Results from outside hospitals can be used as a reference, but must be revalidated if prenatal diagnosis is involved. Problems with interpretation of MECP2 gene test results: Because our hospital often detects mutations that have not been reported internationally and whose pathogenicity is not confirmed, or some mutations whose pathogenicity is in doubt, further verification and detailed explanation to the parents of the child is required. However, for various reasons, in practice, some parents do not communicate with the specialist and simply take the information on the locus to correspond to the symptoms and treatment, which is very detrimental to the confirmation and treatment of RTT disease. Therefore, the sequencing report of RTT issued by our hospital only states whether there are mutations or deletions, duplications, etc. The specific mutations and pathogenicity and other related information and the report are given directly to the pediatrician by us. The parents of the child pick up the report from the Behavioral Center and the specialist will explain it. Regarding the testing of parents of children with RTT: If blood is drawn at the time and the child is sequenced for an unknown de novo mutation, the parents will be sequenced at the same time for the locus to confirm whether it is a genetic marker and to give the results. Other parents will not be tested.