VARIABLE RESPONSE TO THE DIEPOXYBUTANE TEST IN 2 DIZYGOTIC TWINS WITHFANCONI ANEMIA AND FLOW-CYTOMETRY FOR DIAGNOSIS CONFIRMATION

Fanconi's anemia (FA) is a rare, genetically heterogeneous, autosomal recessive disorder characterized by bone marrow failure, congenital ab normalities, chromosome instability, and increased susceptibility to n eoplasia. Congenital abnormalities vary in location and in severity an d not all patients are affected. Although the primary defect of FA is unknown, hypersensitivity to the clastogenic effect of agents that int roduce cross-links in the DNA, such as diepoxybutane (DEB), is a marke r of the FA phenotype in patients suffering from aplastic anemia witho ut the physical characteristics of the syndrome and, conversely, in ca ses with abnormalities in the preanemic phase. We report the case of t wo dizygotic twins suffering from FA with discordant hematologic data. The DEB test repeated several times in various laboratories yielded c onflicting results, whereas cell cycle studies by flow cytometry revea led a pattern typical of FA patients Moreover, the flow cytometric pat tern was correlated with the clinical severity of the disease.