Reproductive decisions after prenatal diagnosis in neurofibromatosis type 1: importance of genetic counseling.

Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant disorders affecting approximately 1/3500 individuals in all ethnic groups. It is characterized by cutaneous and plexiform neurofibromas, café-au-lait spots, Lisch nodules, freckling in axillary and inguinal regions, optic gliomas and an increased risk of malignancy. The mutation rate of NF1 is one of the highest known for human disorders: approximately 50% of all affected individuals carry de novo mutations. Detection of disease causing mutations in the NF1 gene allows presymptomatic and prenatal diagnosis, but is complex and time-consuming due to the large size of the gene, the existence of pseudogenes, the lack of clustering of the mutations in a particular region of the gene, and the variability of clinical findings. Because the time for investigations in prenatal diagnosis is restricted, detection of disease-associated NF1 alleles is more rapid and useful especially for familial cases. Therefore, genetic diagnosis of NF1 is frequently performed by linkage analysis. In our laboratory, 37 families were characterized with this method, of which two requested prenatal diagnosis. One fetus was found to be under NF1 risk. However, parents elected to continue pregnancy: the child is now 2.5 years old and has NF1 features. The phenotypic variability and the absence of genotype-phenotype correlation create difficulties in reproductive decisions for NF1 families, underlining the importance of appropriate counseling and detailed discussion of possible outcomes before genetic testing of the fetus.