Neurofibromatosis is a causally non-specific neural crest dyplasia, which occurs per se as an autosomal dominant mutation in neurofibromatosis von Recklinghausen (NFvR) and in the neurofibromatosis-Noonan syndrome (NFNS). The NFNS probably is a nosologically discrete, real biological entity, ie, apparently not an unusual form of the NS or of NFvR. The NFNS is a relatively common condition, ascertained almost as commonly as NFvR itself. Pathogenesis of the NFNS is unknown, but there seems to be an interesting sex difference in that NFNS males are more likely to have fusiform swelling of nerve strands, while females are more likely to show the classic cutaneous neurofibromata seen in NFvR. NFNS patients seem to have few to no Lisch nodules, but a propensity to the development of retroperitoneal/visceral (ganglio) neurofibromatosis, at times of spectacular extent. Cause of the NFNS is unknown; the known cases are sporadic, but a hint of increased paternal reproductive age may indicate an autosomal dominant new mutation. Since neurofibromatosis is a causally nonspecific dyplasia (all dyplasias are, by definition), and an increased incidence of dyplasia is to be expected in the Ullrich-Turner syndrome (as it is in all aneuploidy syndromes), it would not surprise us to find bona fide UTS patients with multiple neurofibromata. However, at the moment we think it more likely that the purported occurrences of such in the literature represent NFvR women with pleiotropic effect of the mutant gene on ovarian development.
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