Besides the characteristic hallmarks of NF1, specific clinical manifestations occur at an increased frequency in patients with NF1 microdeletions, such as a large numbers of early-onset neurofibromas, dysmorphic facial features, cognitive deficits and an increased risk for the development of malignant peripheral nerve sheath tumors (MPNSTs) [14,17]. The gene discussed is NF1; the disease is plexiform neurofibroma.