[Chromosome instability syndromes].

Chromosome instability syndromes are defined by either an increase of chromosomal breakage or by an increase of sister chromatid exchange number, or by an increase of the two. Bloom's syndrome, Ataxia telangiectasia, Fanconi's Anemia are the main components of this group. The incidence of cancers or malignant blood diseases is high. The finding of DNA repair abnormalities in some of them and their high sensitivity to particular mutagenic agents make these syndromes an interesting model for oncogenesis.