NF1 and Global developmental delay: Indeed, the relatively mild clinical phenotype of group #2 atypical NF1 deletion patients with two copies of SUZ12 suggests that SUZ12 hemizygosity is highly likely to influence the more severe clinical phenotype observed in patients with type 1 NF1 microdeletions characterized by facial dysmorphic features, reduced cognitive abilities and severe global developmental delay, all of which were absent in patient 310221.