The patient has a history of a segmental distribution of café-au-lait macules and freckling involving the right abdomen and right inguinal area, which were first noted at six months of age. First described in 1969 by Nicolls, this phenomenon results from a somatic mutation in the NF-1 gene. Studies have suggested that the appearance of segmental neurofibromatosis is 10 to 30 times less frequent than neurofibromatosis type I. Using fluorescent in-situ hybridization, a neurofibromatosis type I microdeletion was identified in a patient with segmental neurofibromatosis with café-au-lait macules and freckles confined to a single body region. The microdeletion was present in a mosaic pattern in the café-au-lait spot macules, but was absent from normal skin as well as peripheral blood.
Our patient had a normal NF-1 protein truncation assay. However, this assay is limited by a 60 percent sensitivity rate. NF-1 gene sequencing is currently in progess. NF-1 gene sequencing has a 95 percent detection rate for mutations in the NF-1 gene. A skin biopsy from affected tissue with examination for a somatic NF1 gene mutation would confirm the diagnosis of segmental NF.
Individuals with segmental neurofibromatosis have been reported to have children with typical neurofibromatosis type-1. The mechanism for this observation is the small but possible risk of the somatic gene mutation affecting the germ cells of the ovaries or testicles.
Ingordo, V, D'Andria, G, Mendecini, S, Grecucci, M, Baglivo, A. Segmental neurofibromatosis: is it uncommon or underdiagnosed? Arch. Derm. 131: 959-960, 1995.
Nicolls, EM. Somatic variation and multiple neurofibromatosis. Hum. Hered. 19: 473-479, 1969.
Oguzkan S, Cinbis M, Ayter S, Anlar B, Aysun S. Familial segmental neurofibromatosis. J Child Neurol. 2004 May;19(5):392-4.
Online Mendelian Inheritance in Man
Tinschert, S, Naumann, I, Stegmann, E, Buske, A, Kaufmann, D, Thiel, G, Jenne, DE. Segmental neurofibromatosis is caused by somatic mutation of the neurofibromatosis type 1 (NF1) gene. Europ. J. Hum. Genet. 8: 455-459, 2000.
Wolkenstein, P, Mahmoudi, A, Zeller, J, Revuz, J. More on the frequency of segmental neurofibromatosis. (Letter) Arch. Derm. 131: 1465, 1995.
segmental multiple light brown 0.4-2 cm well demarcated macules