[Screening for fragile X syndrome. International experiences].

Fragile X syndrome (FXS) is the most prevalent cause of inherited mental retardation, and calculations show that there are approximately 700 non-diagnosed cases in Denmark. Since the disease is severe, screening for FXS should be considered in order to improve genetic counselling. International experience indicates that efforts should initially be on active case finding among persons with learning difficulties and subsequently on cascade screening to identify carriers. Prenatal screening programmes may be an option when reliable high-throughput diagnostic methods are available.