Cytogenetic sensitivity of three Fanconi anemia heterozygotes to bleomycin and ionizing radiation.

It is well known that Fanconi anemia (FA) patients show a hypersensitivity to the effect of cross-linking agents such as mitomycin C and diepoxybutane, while the sensitivity of these patients to ionizing radiation is controversial. Fanconi anemia heterozygotes do not show a hypersensitivity to the above-mentioned agents. However, bleomycin it is used to identify mutagen sensitive individuals, especially among head and neck cancer patients. We present here a preliminary study in which the mean frequencies of bleomycin-induced chromatid breaks (ctb) from three FA heterozygotes (X = 0.90, range 0.80-1.01) and 11 controls (X = 0.40, range 0.21-0.66) differ significantly (P<.001), indicating a high sensitivity to bleomycin of G(2) lymphocytes from these three FA heterozygotes. An increased sensitivity was not observed after exposure of G0 lymphocytes to 2 Gy of ionizing radiation.