ACTB and immunodeficiency disease: Interestingly, the clinical features exhibited by patients with loss of DIAPH1 or missense mutations in β-actin or γ-actin, such as microcephaly, growth retardation, immunodeficiency, intellectual disability, seizures and hearing loss, are highly reminiscent of those typically associated with the DNA repair deficiency disorders Nijmegen Breakage Syndrome (NBS, OMIM:251260) and Warsaw Breakage Syndrome (WABS, OMIM:613398)24–26.