In addition, many patients with NF1 microdeletions exhibit features which are not usually observed in patients with pathogenic variants within the NF1 gene including facial dysmorphic features, overgrowth, severe global developmental delay and intellectual disability (reviewed by Kehrer-Sawatzki et al. 2017, 2020; Ottenhoff et al. 2020). This evidence concerns the gene NF1 and Global developmental delay.