A rare form of combined immunodeficiency with characteristics of microcephaly, growth retardation and T and B cell lymphopenia. Patients present in childhood with growth retardation, microcephaly, urogenital and bone malformations, dysmorphic features, including bird-like facial dysmorphism, and features of combined immunodeficiency. Some patients may also present with autoimmune cytopenia. This disease is caused by mutations in the NHEJ1 (or Cernunos) gene (2q35). The resulting defect of Cernunnos/XLF, a core protein of the non-homologous end-joining (NHEJ) pathway, affects the major mechanism of DNA double-strand break repair. Transmission is autosomal recessive. [from
SNOMEDCT_US]