Caracterización clínica, citogenética y molecular de un nuevo caso de síndrome de Nijmegen en Chile

The Nijmegen Breakage Syndrome (NBS) is a rare autosomal recessivedisorder associated with microcephaly, immunodeficiency, chromosome instability and cancer prone-ness. The mutated gene that results in NBS codes for nibrin (Nbs1/p95), a DNA repair protein that isfunctionally linked to ATM, the kinase protein product of the gene responsible of ataxia-telangiectasia(A-T). We report the clinical, cytogenetic and molecular characterization of a second case of NBS inChile detected by us. The patient is a 7 years old Chilean boy from a consanguineous marriage, withmicrocephaly, immunodeficiency and acute non lymphocytic leukemia (ANLL). As NBS shares chro-mosomal and cellular features with A-T, the cytogenetic studies of this patient also included 3 A-T pa-tients. Our results showed that the frequency of spontaneous and X rays induced chromosomal aberra-tions in NBS are higher than in A-T cells. DNA analysis revealed that the patient is homozygous for theSlavic mutation 657del5 in the NBS1 gene. This finding and the absence of nibrin in patient’s cells,confirmed the clinical diagnosis of NBS in our patient (Rev Med Chile 2004; 132: 211-18).(