Through exome sequencing, the NIH Undiagnosed Diseases Program (NIH UDP), a clinical site of the NIH Undiagnosed Diseases Network (UDN), identified a variant (M280L) in a single allele of the FOXR1 gene (forkhead box R1; NM_181721.2) in an individual with severe neurological symptoms including postnatal microcephaly, progressive brain atrophy, and global developmental delay. The gene discussed is FOXR1; the disease is Global developmental delay.