Cytogenetic and dermatoglyphic studies were carried out in Down's Syndrome (DS) malformed girl aged 2 years, suffering with Acute Lymphoblastic Leukemia (ALL) as well as in her healthy parents. The malformed leukemic girl has about 90 percent of the analysed metaphases with the modal number 47 XX + 21, but in 15 percent of the same metaphases one notices t (9;22)(q34;q11) coexisting with trisomy 21. The mother has an inconsistent chromosomal change and the father is cytogenetically normal. The proband child's fingerprints distribution is partly similar to the mother's, but while the diseased girl has a simian line (SL) in her left hand, the healthy Father has a F1 transition form of palmar flexion creases in the left hand too. We have analysed two coexistent types of chromosomal aberrations in some metaphases of the proband girl who combines only some dermatoglyphic characteristics which are similar to each of the parents. Although the molecular basis is not known but partly in restructuring and/or repositioning of the genes in coexistent chromosomal changes we have suggested a possible way of expressing predispositional potential in leukemogenesis in which the chromosomes 21 and the genes located in them are implied.