It is no longer magical that a single tube of blood can be drawn to check whether a person will have the disease, what type the disease belongs to, the severity of the disease, or even to make an assessment before birth. Motor neuron disease is rare clinically, but there are many types, variants and dangers. In the past, diagnosis relied mostly on clinical manifestations, EMG and muscle biopsy results, and long diagnostic cycles. In the last decade or so, with the maturation and speed of genetic diagnosis technology, it has become possible to gradually shorten the clinical diagnosis time. Although the Human Genome Project, in which Chinese scientists participated, completed the first human genetic sequence map in 2001, which was a world sensation. In practice, however, the importance of practical application in China is far from adequate, and the public is not sufficiently aware of genetic diagnosis and prenatal diagnosis. Some people are afraid of genetic diseases and fear discrimination if their family, friends and colleagues know about them. In one example, our hospital used genetic analysis to definitively diagnose a case of medullary spinal muscular atrophy, also known as Kennedy’s disease, which is an inherited neurodegenerative disease and belongs to a type of motor neuron disease. It is often confused with other types of motor neuron diseases. Its main manifestations are slowly progressive muscle weakness and atrophy of the throat, face and limb muscles in men with adult onset, which may be accompanied by androgen insensitivity such as gynecomastia and reduced reproductive function. It was found that the copy number of the trinucleotide repeat sequence p(CAG)n on the first exon of his androgen receptor gene increased to 50 (normal repeat number range is 11 to 29). We recommended that both his mother and daughter undergo genetic analysis, as this is an X-linked disorder, but the patient was reluctant to have his family examined. This situation exists both nationally and internationally, and doctors usually respect the patient’s wishes. But the problem is that his daughter is most likely a carrier of this mutation gene. If it is determined that his daughter is a carrier of the mutation gene, the birth of a sick child can be completely prevented by examining the fetus before its delivery to determine if it is a healthy boy. But now his daughter is risking the possibility of having a boy (grandson) with the same disease as him. And with the adult onset of this disease, treatment is limited and her life will be spent experiencing unnecessary illness. It is also common to meet women in the clinic who are 6-7 months pregnant and who have just heard that prenatal diagnosis is possible because they have a family history of spinal muscular atrophy (most of them have died), so they come to ask how to do it. In fact, the best time for prenatal genetic diagnosis is lost at this time, and the doctor is unable to help the consultant because of regulatory and ethical requirements. It is not uncommon to have 1 or 2 children with the same disease in the family. One of the most common types of motor neuron disease in adults is called amyotrophic lateral sclerosis, which is hereditary in 20% of cases, with mutations in the SOD1 gene being the most frequent. We can do analysis of all its exon mutations, but the number of cases with family history asked in the clinic is much less than international reports, mostly because patients do not want to classify their disease as a genetic disease and do not want to say that they have similar patients in their family. We had a patient who was diagnosed and then asked about his family history only to find out that six people in his family had the disease, and genetic analysis was done to determine that there was a mutation in the SOD1 gene. So rational understanding is necessary to make scientific and technological advances for the benefit of the public.