NF1 and plexiform neurofibroma: The NF1 gene was cloned in 1990.9,10 Subsequent cell biology studies have found that neurofibromin, the NF1 gene product, largely operates as a GTPase-activating protein (GAP) that negatively regulates the RAS/MAPK pathway activity by accelerating the hydrolysis of RAS-bound GTP.1 Cell biology advances and animal models have led to the identification of MEK inhibitors as a treatment for plexiform neurofibromas.11 In April 2020, selumetinib was approved by the US Food and Drug Administration for treatment of children with NF1-related symptomatic plexiform neurofibroma.11