Neurofibromatosis 1 (NF1) occurs in 1:2000 births. The
main diagnostic signs are visible on the skin, and this opens several
interesting aspects for dermatological point of view. The NF1 syndrome
is caused by mutations in the NF1 gene which encodes the tumor
suppressor protein neurofibromin. Neurofibromin functions as a
Ras-GTPase-activating protein (RasGAP), and NF1 mutations lead to
overactivation of the Ras signalling pathway. The NF1 gene and
neurofibromin have intriguing functions in keratinocytes and
melanocytes. Neurofibromin regulates melanin synthesis and keratinocyte
differentiation in a currently unknown manner. The NF1 gene has also an
important but poorly understood role in tumorigenesis and cancer.
Compared to the general population, NF1 patients have a fivefold risk
for cancer and a more than 2000-fold risk for neurogenic malignancies.
Mutations of the NF1 gene are common in numerous cancer types in
patients without NF1, and this suggests a more general role for the NF1
gene in oncogenesis. In melanoma, NF1 mutations seem to drive
tumorigenesis and contribute to drug resistance. In this article, we
review the literature on neurofibromin with special attention to
keratinocytes, melanocytes, NF1-related tumors and melanoma.