Skin abnormalities in neurofibromatosis .2.

Objective: To determine the prevalence, distribution, and histopathological conditions of skin abnormalities in neurofibromatosis 2 (NF2). Design: Case series. Setting: Hospital neurology department. Patients: Consecutive sample of 88 patients with NF2 referred through workshops and publications, genetic counseling, and referral from neurosurgical departments; 81 patients met the National Institutes of Health, Bethesda, Md, NF2 diagnostic criteria and the diagnosis was established by mutation or segregation analyses in 7 patients. Main Outcome Measures: Prevalence, distribution, and type of skin abnormalities; histopathological features of 29 skin tumors selected primarily for medical indications. Results: Fifty-two patients (59.1%) had 458 skin tumors, which were the first presenting sign in 27.3% of patients and usually appeared as flat dysplastic tumors or subcutaneous spherical nodular tumors of the peripheral nerves, on the limbs and trunk. Although 29 patients (33.0%) had cafe au lait spots, only 2 patients had as many as 6 spots. Compared with patients with milder disease, patients with more severe disease had a significantly greater prevalence of skin tumors (24.0% and 71.0%, P<.001), more than 10 skin tumors (0.0% and 27.4%, P=.004), flat dysplastic skin tumors (8.0% and 54.8%, P<.001), and subcutaneous spherical nodular tumors (24.0% and 58.1%, P=.004). The histologically analyzed tumors were predominantly schwannomas, but 5 were neurofibromas and 2 were mixed tumors. Conclusions: The prevalence of some skin tumor types in NF2 is high and varies with disease severity, and schwannomas predominate in sampled tumors. The occurrence of neurofibromas is surprising, but could be explained by an interaction between neurofibromin and the NF2 gene product in regulating the ras proto-oncogene.