Microcephaly with bird-like facial dysmorphia may be observed at birth in cases of DNA Ligase IV deficiency (LIG4), Nijmegen breakage syndrome (NBS1), and Cernunnos-NHEJ1 deficiency (NHEJ1) (6, 7). The gene discussed is NHEJ1; the disease is hyperinsulinemic hypoglycemia, familial, 4.