Most known genetic diseases are rare but taken together, they affect 2% to 3% of the population. Around 15,000 to 20,000 new patients are recorded each year in France. Many of these pathologies are severe, affecting life expectancy and quality of life while only a small minority currently has curative treatment. The unexpected diagnosis of such an illness is a tragedy that disrupts the life of the family circle. Could we consider preventing them?
It seems a priori surprising to ask the question to the extent that these diseases are the consequence of the transmission of a genetic anomaly (mutation) carried by each parent in the majority of cases or by only one, the mother if It is a transmission disease linked to the X chromosome, such as hemophilia for example. When the risk is known due to family history, we can offer, for severe illnesses and if the family so wishes, a prenatal diagnosis which can lead to termination of the pregnancy if the fetus is affected or to a preimplantation diagnosis after in vitro fertilization and selection of unaffected embryos. But in the absence of a history, the majority of cases, what solutions?
Since the 1970s, has been proposed in populations where a genetic disease was common (thalassemia, a form of serious anemia in Sardinia, Sicily and Cyprus or Tay-Sachs disease, a neurodegenerative disease in Ashkenazi Jews), to identify, through blood characteristics, people at risk of transmitting these diseases to their children (with a risk of 25%). Such programs, very well accepted by these populations, have made it possible to greatly reduce the occurrence of these diseases. Since the 1980s, advances in genetics have made it possible to directly detect people carrying mutations. Today, it is becoming possible to identify such mutations in a very large number of genes. As a result, an offer for the detection of mutations shared by a couple (or located on the chromosome) has been set up in a few countries (around ten including Australia, Israel, the United States). maternal X) leading to a risk of the birth of a child with a serious genetic disease. The number of diseases concerned varies from one country to another depending on the prevalence and severity of the disease, with tests being paid for by the community or not. Until recently, there was very little information on the usefulness and feelings of couples about such programs. A recent large-scale study carried out in Australia provides some very interesting answers.
A beneficial diagnosis
Among 9,100 couples who used this analysis, most before any conception, just under 2% were identified as having a 25% risk of transmission of one of the 750 diseases (genes) tested. In 3 out of 4 cases, families decided to take this information into account by opting for a prenatal diagnosis or a preimplantation diagnosis during a pregnancy. The investigation showed that the announcement of the risk generated an understandable amount of anxiety but which proved to be transitory. Transposed to the scale of France, this would amount to detecting 14,000 couples at risk each year and avoiding the birth of around 2,000 to 3,000 children suffering from serious genetic diseases. It was proposed during the last revision of bioethics laws to open the door to preconception genetic diagnosis of serious genetic diseases but this possibility was rejected by the Minister of Health at the time in the name of a risk of eugenics.
Obviously such a diagnosis must be strictly regulated in terms of information, quality of announcement of the results of this screening and strict respect for the choice of couples to use it or not, and to draw the conclusions they wish to take. . This involves providing support for couples at risk. This screening should be reserved for particularly severe illnesses and be subject to careful monitoring. Equity requires that its cost be covered by Health Insurance to allow fair accessibility. Hopefully this new information will convince public authorities to move forward.
Alain Fischer is president of the Academy of Sciences and co-founder of the Institute of Genetic Diseases
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