NF1 and plexiform neurofibroma: Segmental neurofibromatosis is a rare variant of NF1 (estimated prevalence between 0.0014 and 0.002%) characterized by neurofibromas and/or café-au-lait macules localized to one body segment with no crossing of the midline and no family history (since it results from a post-zygotic NF1 mutation leading to somatic mosaicism) [269].