Cutaneous and Systemic Findings in Mosaic Neurofibromatosis Type 1

Background/Objectives Mosaic neurofibromatosis type 1 (MNF1) is a variant of neurofibromatosis type 1 (NF1) in which clinical manifestations are limited to one or several body segments. The objective was to characterize the cutaneous features and associated systemic findings in a cohort of children with MNF1. Methods We performed a retrospective study of 40 children diagnosed with MNF1 at the Department of Dermatology, Hospital Infantil Nino Jesus, Madrid, Spain, from January 1, 1986, to October 31, 2015. Results All patients had pigmentary changes, alone (n = 39) or in combination with neurofibromas (n = 1). Twenty-four cases fulfilling the definition of MNF1 had six or more cafe au lait spots with or without freckling within the affected segment. They all lacked any other National Institutes of Health criteria of NF1. No patient had juvenile xanthogranuloma (JXG) or nevus anemicus (NA). Two children with MNF1 had epilepsy and two others developed malignancy (Hodgkin's lymphoma and ganglioneuroblastoma). Conclusions Pigmentary changes are the most frequent presentation of MNF1 in children. MNF1 must be considered with segmentary distribution of freckling and cafe au lait spots. Other frequent cutaneous findings in NF1, such as JXG or NA, seem to be exceptional in MNF1. Although the possibility of systemic complications and cancer risk seem to be low, patients must be followed up.