NF1 and plexiform neurofibroma: Since the first identification of patients with NF1 microdeletions, it became clear that these patients often present with a severe clinical phenotype and exhibit features which are not common in patients with intragenic NF1 mutations including facial dysmorphic features, severe learning disabilities, high numbers of neurofibromas, overgrowth/tall-for-age stature, large hands and feet with excessive soft tissue, hyperflexibility of joints and congenital cardiac anomalies [8, 15–21].