[Prenatal diagnosis of cutaneous genetic diseases by the study of fetal DNA].

There has been considerable progress in chromosome mapping and gene identification in several severe hereditary skin diseases, leading to changes in genetic counseling. It is now possible to propose antenatal diagnosis to couples at risk based on an analysis of foetal DNA from trophoblast biopsies performed as early as the 9th week of gestation. Antenatal can be made by direct analysis based on identifying the mutation known in the family at risk or on indirect analysis based on the linkage disequilibrium of the allele or alleles associated with the disease in the family at risk. This method has already been shown to be effective in recessive dystrophic bullous epidermolysis, lethal Herlitz's junctional bullous epidermolysis, bullous ichthyosiform hereditary erythroderma, von Recklinghausen's neurofibromatosis, tyrosinase negative oculocutaneous albinism, Gorlin's syndrome, anhidrotic ectodermic dysplasia and Menkes disease. These techniques will replace microscopic examination of ultrastructure in foetal skin biopsies performed at 20 weeks gestation. They can also be applied to diseases where the antenatal diagnosis now relies on enzyme function tests or DNA distribution. Improving genetic counselling in these diseases requires the identification of the implicated genes, identification of the causal mutations in the families at risk and development of genetic markers for these diseases.