IDENTICAL CYTOGENETIC CLONES AND CLONAL EVOLUTION IN PEDIATRIC MONOZYGOTIC TWINS WITH ACUTE MYELOID-LEUKEMIA - PRESYMPTOMATIC DISEASE DETECTION BY INTERPHASE FLUORESCENCE IN-SITU HYBRIDIZATION AND REVIEW OF THE LITERATURE

Purpose: Observation of identical acquired genetic changes in infant m onozygotic (MZG) twins with acute leukemia has provided strong evidenc e for in utero twin-twin transfusion as the cause of concordance. Docu mentation of similar phenomenon in older MZG twins offers insight into the latency period for leukemia and may provide the opportunity for p resymptomatic disease detection in one twin. Design: The literature de scribing leukemia in MZG twins is reviewed and the results of classica l and molecular cytogenetic studies of one pair of MZG twins at 3 and 4 years with acute nonlymphocytic leukemia-FAB type M1 are reported. R esults: The twins studied had cytogenetically identical neoplastic clo nes with identical clonal evolution. Retrospective fluorescence in sit u hybridization studies demonstrated the presence of the abnormal clon e in the asymptomatic twin at the time of bone marrow transplant of th e first twin. Conclusions: These observations support in utero twin-tw in transfer as the origin of leukemic clones in pediatric and infant l eukemia, demonstrate that clonal evolution of a leukemic clone may occ ur years before onset of overt disease, and indicate that knowledge of acquired genetic change(s) in one twin may provide markers to assess disease in the asymptomatic twin.