Frequency of 657del(5) mutation of the NBS1 gene in the Czech population by polymerase chain reaction with sequence specific primers.

Nijmegen breakage syndrome is an autosomal recessive chromosomal instability syndrome characterized by microcephaly, immunodeficiency, radiosensitivity, and predisposition to lymphoid malignancy. A truncating deletion [657del(5)] in exon 6 of the nibrin NBS1 gene is the most frequent cause of the syndrome. Slavic populations carry this mutation in a high frequency.