Comet assay and cytogenetic findings in differential diagnosis of fanconi anemia

Fanconi anemia (FA) is a complex genetic disease with a variety of congenital and hematological symptoms, including the predisposition for cancer development. The main hallmark of FA cells, an increased chromosomal fragility, in the presence of the DNA-interstrand cross-linking chemicals, mitomycin C or diepoxybutane (DEB), makes the diagnosis of FA much easier. Cytogenetic method can detect the FA patients with highly elevated chromosomal breakage, but also some of the patients with borderline sensitivity to DEB no matter if they have FA or not. These particular circumstances lead us to introduce comet assay along with cytogenetic analysis, in order to determine DNA lesions and chromosomal fragility in untreated and DEB-treated lymphocytes of full blood from seven patients with clinical features of FA. Highly elevated DEB induced chromosomal sensitivity confirmed the diagnosis in five patients (FA group: 0.48-4.47 breaks/cell vs control group: 0.00-0.08 breaks/cell). Borderline DEB sensitivity (FA* group: 0.15-0.44 breaks/cell) was found in the remaining two patients. Results of the comet assay showed higher baseline and DEB-induced DNA damage values (Olive tail moment and tail intensity) in all five FA and one FA* patient, when compared to the control group. These findings could provide a new model of FA screening test algorithm, including comet assay as additional and very useful accurate tool, beside the DEB test, in differential diagnosis of FA