Mutations at the homozygous status in the NBS1 gene (known also as NBN) are responsible for a rare disease known as Nijmegen breakage syndrome (NBS; OMIM 251260), an autosomic recessive disorder whose signs are a distinct facial appearance, microcephaly, immunodeficiency, chromosome rearrangements and sensitivity to ionising radiation [1]. Here, NBN is linked to Nijmegen breakage syndrome.