Today is International Rare Disease Day, with over 7000 confirmed rare diseases worldwide. Common rare diseases include hemophilia, ALS, phenylketonuria, osteogenesis imperfecta, etc. It is estimated that there are approximately 60 million patients with various rare diseases in China. What is a rare disease? What is the relationship between rare diseases and genetics? There are about 60 million rare disease patients in China. Rare diseases refer to diseases with extremely low incidence and a small number of patients. About 50% of rare diseases occur in childhood, and currently only about 5% of rare diseases have effective treatment methods. About 80% of rare diseases are caused by genetic defects. We each have 5-10 defective genes in our bodies, and once both spouses have the same defective genes, it is possible to have children with physical defects. The possibility of close relatives carrying the same recessive pathogenic gene is high, which increases the incidence of rare diseases in their children. Why do parents have healthy children but genetic diseases? In daily life, it is common to encounter situations where both husband and wife are healthy, but the child has birth defects or even rare diseases. Why is that? Let's listen to what the experts have to say. Experts say that recessive genetic diseases can lead to birth defects. Both or one spouse may carry a certain disease causing gene or abnormal chromosome, and although they do not have the disease themselves, they may pass on the disease causing gene to their offspring, leading to the offspring developing the disease. Jiang Yulin, Deputy Director of the Obstetrics Center at Peking Union Medical College Hospital: Hidden genetic diseases can indeed be transmitted through generations, but they are relatively hidden. We advocate couples who are preparing for pregnancy to undergo genetic disease screening before pregnancy in order to reduce the risk of genetic diseases and fertility. Targeted measures can be taken to avoid these diseases. Another reason for birth defects is genetic mutations in the fetus. Both husband and wife do not have any chromosomal or genetic related genetic diseases, but the child has a genetic disease. The most common types are Down syndrome, as well as albinism, hemophilia, megaloblasm, color blindness, etc. Almost all parents of children with Down syndrome have normal chromosomal phenotypes. Environmental influences may also lead to birth defects. Although both husband and wife are healthy, due to the presence of certain teratogenic factors in the environment during pregnancy, it is also possible to have unhealthy children. Common teratogenic factors include physical factors such as radiation, ultrasound, and high fever, chemical substances such as heavy metals and pesticides, as well as various viruses and drugs. Experts explain that due to the low incidence and complex symptoms of rare diseases, a survey by the China Rare Disease Alliance shows that about 40% of rare disease patients have experienced misdiagnosis or missed diagnosis. Is there any way we can prevent the occurrence of rare diseases, as they are so difficult to diagnose? Tian Zhuang, Chief Physician of the Department of Cardiology at Peking Union Medical College Hospital: In the field of rare diseases, there is a saying: "Doctors who can see rare diseases may be even rarer than rare disease patients." Doctors who truly understand this disease may not have one or even one in a primary hospital, and patients often go to many hospitals to complete the diagnosis. Therefore, this is a global challenge, and rare diseases are difficult to diagnose. China implements a three-level prevention strategy for birth defects to minimize the birth of rare disease patients. Primary prevention refers to prevention before marriage and pregnancy. Secondary prevention refers to the detection of rare diseases through prenatal screening and diagnosis during pregnancy. Third level prevention is newborn screening, early diagnosis and treatment of rare diseases before they occur. Jiang Yulin, Deputy Director of the Obstetrics Center at Peking Union Medical College Hospital: Before pregnancy, both couples should undergo some physical examinations to see if there are any chronic diseases. After pregnancy, supplementing intake of folic acid during early pregnancy can effectively reduce the occurrence of common birth defects, such as neural tube defects and congenital heart disease. It is very important to have regular prenatal check ups throughout the entire pregnancy, and at the same time, to control nutritional weight, balance diet, and maintain a good mentality during pregnancy. At present, there are more than 20 rare diseases that can be screened in the newborn disease screening process, mainly genetic metabolic diseases. Through early intervention and long-term control, the condition of the child can be basically stabilized. Experts remind to avoid excessive anxiety during prenatal check ups. The purpose of prenatal check ups is to monitor maternal and infant health, but frequent or unnecessary checks may have the opposite effect. This not only increases the psychological pressure and economic burden on pregnant women, but also leads to unnecessary medical interventions. Jiang Yulin, Deputy Director of the Obstetrics Center at Peking Union Medical College Hospital: Each genetic testing technique should have clear medical indications. We need to choose appropriate genetic diagnostic techniques based on what happens to the child or how high the genetic risk is in this family. Avoiding the birth of severely disabled children is not about selecting "perfect" children. (New Society)