Segmental neurofibromatosis in childhood.
Segmental neurofibromatosis refers to individuals who have manifestations of neurofibromatosis type 1 (NF-1) limited to one area of the body. It results from a post-conceptional mutation in the NF-1 gene leading to somatic mosaicism. Although it is generally considered a rare condition, this report of 39 children with segmental NF-1 demonstrates that it is commonly seen in a pediatric NF-1 referral center. The mean age at diagnosis was 7.8 years (range: 2-25 years). Twenty-nine patients had only pigmentary manifestations of segmental NF-1, including seven who had only café-au-lait macules and 22 who had café-au-lait macules and freckling. Two patients had isolated plexiform neurofibromas; a third patient had a plexiform neurofibroma of the eyelid in addition to ipsilateral dysplasia of the sphenoid wing and Lisch nodules. A 12-year-old girl had an isolated tibial pseudarthrosis. An 8-year-old boy had an isolated optic pathway tumor, which behaved both biologically and radiographically as an NF1-associated tumor. While most children with segmental NF-1 have only localized pigmentary changes, some children will have isolated plexiform neurofibromas, pseudarthroses, or optic pathway tumors. Accurate diagnosis of segmental NF-1 is crucial for both management and genetic counseling.