A common confusion and misunderstanding is to link genetic diseases with family history. The history and biology textbooks of genetics make it easy for you to associate genetic diseases with complex family maps, thinking that only diseases with family history are genetic diseases. Actually, it is not. There are few genetic diseases that can see the typical family map, and most patients with genetic diseases cannot trace their family history through the family map. In fact, most patients with genetic diseases are sporadic cases without family history. The reason why there is no family history of genetic diseases is related to the pathogenesis of genetic diseases. Most genetic diseases with typical family history belong to X-linked recessive genetic diseases and non-fatal autosomal dominant genetic diseases. When the family is large enough, both forms of genetic diseases will cause obvious family onset tendency, and patients and their families can usually describe a typical family history. As the most common single-gene disease, autosomal recessive genetic disease is rarely seen with family history. Because the onset of autosomal recessive genetic disease is based on the premise that two carriers get married and have offspring, no matter how long the pathogenic gene is passed on in the family, there may never be a patient born with this genetic disease-the carrier in the family must meet another carrier in the crowd to have offspring, and such a thing will happen. The carrier rate of most recessive genetic diseases is relatively low, which is why it is difficult to trace back to the birth of the same patient in the family. Some people think that dominant genetic diseases should have a clear family history, but this is also a wrong understanding. Although the dominant genetic disease seems to have a clear family genetic history, because as long as you carry genes, you will get sick. But because of this, many patients with serious genetic diseases cannot survive, so they cannot form a family. For recessive genetic diseases, carriers with pathogenic genes are asymptomatic; For dominant genetic diseases, there are no carriers, only patients and normal people. If the patient dies, there is no possibility for the family to inherit. Therefore, most serious dominant genetic diseases come from new mutations rather than family inheritance. Only those non-fatal dominant genetic diseases will have typical family history manifestations. Similar to monogenic diseases, most chromosome diseases have no obvious family history. The most common chromosomal abnormalities, such as Down syndrome, Turner syndrome, Creutzfeldt-Jakob syndrome, etc. All come from the random error of cell division and have nothing to do with heredity. Although many people will feel puzzled and confused when faced with genetic diseases without family history, you should know that family history is not necessarily accompanied by genetic diseases. Most genetic diseases diagnosed today do not have any traceable family history.