[Mild cystic fibrosis: genetics - extending follow-up is necessary].

The diagnosis of mild cystic fibrosis is first suspected on mild lung disease or absence of pancreatic insufficiency and is assessed by biological analysis. The sweat test is not always conclusive. The nasal potential difference and molecular analysis of CFTR gene allow confirming diagnosis. A regular follow-up in cystic fibrosis clinical centre is essential all life long. The genotype, especially during neonatal period, cannot be used to predict individually the course of the disease. Genetic counselling must be recommended to the parents in order to propose an analysis of CFTR gene to give the appropriate genetic counselling and to consider with them which family members could be concerned, especially in the event of parental project. The research of heterozygote status in related for prenatal diagnosis is not recommended for all mutations.