Not so rare ..: Genetic Diseases

Upstream of the Telethon, the Wyeth Foundation chaired by Professor Claude Griscelli, very involved in the health of the child and adolescent, organized in Paris a round table on "live and be born with a genetic disease," while focusing on the fact that genetic diseases are actually very numerous, researchers discovered an average week.
Some genetic diseases
This round table has three leading experts in the field to speak: Dr. Segolene Ayme, directing and coordinating European Orpha (www.orphanet.fr) encyclopaedia of rare diseases including information on specialized consultations and reference centers on research projects and clinical trials, as well as patient registries and patient associations; Prof. Stanislas Lyonnet Department of Genetics at the Necker Hospital in Paris, Professor Paul Czernichow, pediatrician Necker consultant and president of the Paris Federation for screening and prevention of childhood disabilities.

About 5,000 genetic diseases have been identified, of which 1,000 to 1,500 are recurrent and one hundred heavily. With 30,000 new cases per year, they affect more than 3 million people in France, including a large number of children (two thirds of genetic diseases occurring in childhood and third in adulthood).

In France, the most common are cystic fibrosis (6000 patients), hemochromatosis and hemophilia.

A total of 1% of the population is affected by a genetic disease.

One of the features of genetic diseases is the fear for the person affected, transmit affection to their children or grandchildren. In fact, inheritance is not systematic, it occurs if the modified gene (or mutated) is found in the cells of gametes, eggs and sperm.

A genetic disease will not be transmitted to all the children of an affected parent and vice versa, the parents of an affected child are not necessarily affected by the disease. Thus, many genetic diseases occurring for the first time.

In addition, the impact of genetics appears highly variable from one condition to another and from one child to another. Thus, for type 1 diabetes in genetically insulin-dependent, only 5% of children of diabetic parents will be affected by the disease.

The rate of mutations in the genes is consistently high in the human species. It is due to cosmic and terrestrial radiation and amounts to one in a million per generation. There are also exceptional and other recurrent mutations, some of which can still offer a benefit, as is the case with sickle cell disease (mutation of the gene for hemoglobin, causing a severe chronic anemia), which protects consideration of malaria, or a mutation that allows a few cases of people with HIV to resist the AIDS virus (this is called the "long term survivors").

Penetrance (probability that the variant form of a gene or allele occurs) of an abnormal gene is highly variable and never 100%. The expression of a genetic disease can therefore be observed in offspring without being upstream. In addition, genes that are expressed in offspring depend on what the grandparents have lived. Finally, the existing 20,000 genes in the genome and interact with the environment, even during pregnancy.

No possible prevention
It is impossible to prevent such diseases, genetic mutations inevitably continue to occur and affect some people.

In contrast, thirty genetic diseases can be diagnosed through genotyped in populations at risk. This prenatal or preimplantation diagnosis can support parents facing the announcement of the disease or help in their decision whether or not to continue the pregnancy.

In France, only genetic diseases for which treatment provides health improvement are sought and five are subject to routine screening of newborns by taking a drop of blood on the heel: cystic fibrosis, phenylketonuria, hypothyroidism, congenital adrenal hyperplasia and sickle cell anemia.

Progress thanks to new medical treatments
For most genetic diseases, there can be no question of healing, but sometimes it is possible to stabilize the progression, relieve pain or to decline the most disabling symptoms.

Thus, children born with trisomy 21 today have a life expectancy of over 50 years. Similarly, the understanding of phenylketonuria (accumulation of amino acid in the body, phenylalanine, responsible for mental retardation), has established a specific diet to prevent any symptoms of the disease.

It is the passage from childhood to adult life with a genetic disease that seems to pose more problems as genetic diseases usually cause a deterioration in the quality of life, loss of independence and many suffering to the extent that the uncertainty of the evolution is very difficult to manage. Therefore, the Wyeth Foundation will undertake a project on the history of these diseases and their impact on education, work and family life.