Remarkably, FA-AML1 cells appeared to lack the characteristic cellular FA phenotype, i.e., a hypersensitivity to growth inhibition and chromosomal breakage by the cross-linking agent mitomycin C. Genomic DNA from the patient showed biallelic mutations [8415G>T (K2729N)and 8732C>A (S2835STOP)] in the breast cancer susceptibility gene FANCD1/BRCA2 [N. Howlett et al., Science (Wash. DC), 297: 606-609, 2002].