[Show abstract][Hide abstract] ABSTRACT: Mutations in the FBN1 gene have been characterised in patients affected by Marfan syndrome and Marfan-related disorders. Starting with genomic DNA, we analysed the FBN1 gene using PCR, SSCP and/or dHPLC analysis, and automatic sequencing of abnormal bands/peaks, in a consecutive series of 508 patients, of which 22 were children less than 5 years old. Our results are comparable with those reported by other groups. In this study we observed 193 mutations, 126 of which previously unreported. A total of 331 relatives (including 51 infants) of 120 probands for whom a family mutation had been identified here or elsewhere, were tested for the presence of that particular mutation. In addition, 4 prenatal tests were carried out. The identification of a mutation allows for early diagnosis, prognosis, genetic counselling, preventive management of carriers and reassurance for unaffected relatives. The importance of knowing in advance the location of the putative family mutation is highlighted by its straightforward application to prenatal and postnatal screening.