Differentiation of Fanconi anemia from aplastic anemia by chromosomal breakage test.

Aplastic anemia (AA) is a disorder of heterogeneous pathogenesis caused by diverse etiologies. Fanconi anemia (FA) has the similar features of pancytopenia but is characterized by spontaneous or induced chromosomal instability and a variety of congenital anomalies. A cytogenetic breakage study is used to enable the diagnostic differentiation between FA and the so-called "idiopathic" AA. This method is based on the effect of the bifunctional alkylating agent mitomycin C (MMC) and alkylating mutagen diepoxybutane (DEB) on the chromosomes of peripheral lymphocytes in culture. Among thirty-three new cases of bone marrow failure with unknown etiologies, three young male patients were confirmed as victims of FA. The methodology and clinical manifestations were discussed. A prenatal screening was also performed to exclude the possibility of homozygous FA in one fetus at risk. The adequate dose of MMC used in our tests for diagnosis of FA were 20 ng/mL, while DEB did not work. These findings may suggest genetic diversity or other contributing factors in the pathogenesis of FA.