NKX2-1 and Intellectual disability: In particular, when the deletion includes the genes FOXG1, NKX2‐1, and PAX9, the prognosis is poor, with severe intellectual disability (ID) and central nervous system (CNS) malformations (i.e., agenesis of the corpus callosum [CC]), while more distal deletions, involving only NKX2‐1 and PAX9, appear to be associated with a milder phenotype (Santen et al., 2012).