Unusual response to bifunctional alkylating agents in a case of Fanconi anaemia

Chromosomal breakage frequencies were determined in Fanconi anaemia (FA) blood cultures treated with various concentrations of the polyfunctional alkylating agents mitomycin C, diepoxybutane, and cis-platinum(II)-diammine-dichloride, for which FA cells have a characteristic hypersensitivity. At concentrations that hardly affected control cultures, three out of four patients tested exhibited a concentration-dependent increase of cells with aberrant chromosomes, with a concomitant increase in the number of chromosomal aberrations per aberrant cell. The fourth patient, a 22-year-old male, was exceptional because with all three clastogens only 40% of his cultured cells exhibited a typical concentration-dependent response, while 60% of his cells responded like those from normal healthy controls. The possible nature and significance of this unusual response is discussed.