Abstract: Objective: To identify NF1 mutations in two patients with segmental neurofibromatosis and to provide prenatal diagnosis for these two patients. Methods: Genomic DNA was extracted from two separate dermal lesional tissues of the patients. Next-generation sequencing was performed to identify mutations usingof DNA extracted from dermal tissues of patients skin lesions. Sanger sequencing was employed to verify the NF1 mutations in different tissues. Chorionic villus sampling was performed during pregnancy of the patients and Sanger sequencing was performed. Results: The patients showed unilateral distributed, multiple asymmetrical café-au-lait macules and lentigines, as well as cutaneous neurofibroma. They were diagnosed as segmental neurofibromatosis type 1. Two mosaic mutations in NF1, c.1007G>A (p.Trp336*) and c.1885G>A（p.Gly629Arg）were detectedfound in the genomic DNA of the affected tissues from patients 1 and 2, respectively. Prenatal diagnosis was successfully performed in the two patients based on the above results. Conclusion: Molecular diagnosis of segmental neurofibromatosis is possible through the genetic testing using DNA from affected tissues, and the prenatal diagnosis is feasible based on the genetic results.

Key words: neurofibromatosis, NF1 gene, prenatal diagnosis, mosaic mutations