PRENATAL-DIAGNOSIS OF ATAXIA-TELANGIECTASIA AND NIJMEGEN-BREAKAGE-SYNDROME BY THE ASSAY OF RADIORESISTANT DNA-SYNTHESIS

Prenatal diagnosis was performed in 16 pregnancies at risk of ataxia-t elangiectasia (A-T) or Nijmegen Breakage Syndrome (NBS). Radioresistan t DNA synthesis (RDS) was investigated in cultured chorionic villus (C V) cells and/or amniotic fluid (AF) cells. In four pregnancies, an aff ected foetus was diagnosed with increased RDS in cultured CV cells. In three of the four cases confirmation of the diagnosis was obtained by analysis of AF cells and/or skin fibroblasts from the foetus cultured after termination of the pregnancy; in the fourth case a fibroblast c ulture from the aborted foetus failed. In one case, only AF cells coul d be analysed in a late stage of pregnancy; pregnancy was terminated d ue to intermediate/equivocal results but the foetal fibroblasts showed normal RDS. Normal RDS was demonstrated in the other 11 pregnancies a t 25% risk either by analysis of CV cells (nine cases) or of AF cells (two cases). In some cases the (normal) results on the CV cells were c orroborated by subsequent analysis of AF cells. The results suggest th at RDS analysis of CV cells allows reliable prenatal diagnosis of A-T/ NBS. However, amniocentesis may be necessary to confirm normal results on CV cells if the foetus is female (because of the risk of maternal cell contamination) or in the rare case of equivocal results.