New structural chromosomal rearrangements in congenital leukemia.

The karyotypic abnormalities and clinical data on three patients in whom acute leukemia was diagnosed within the first 6 months of life are presented. The four structural chromosomal rearrangements detected in the bone marrow from these patients, i.e., t(7;12)(q36;p13) and t(1;19)(q11;q11) in case 1, t(2;10;11;12)(q21q31;p13;q13;q24) in case 2, and t(11;19)(q23;p13) in case 3, have not previously been associated with congenital leukemia. Acquired chromosomal changes have until now been reported in only 31 leukemic infants in this age group. Of the total material, 18 patients had acute lymphoblastic leukemia and 16 had acute nonlymphocytic leukemia. The by far most frequently recorded cytogenetic aberration has been t(4q;11q), seen in 14 cases of lymphoblastic leukemia. Although t(4q;11q) has not been found in a single patient with acute nonlymphocytic leukemia, these leukemias have often had other rearrangements involving the same region of 11q. Hence, genetic material around 4q21 may be active in lymphocytic differentiation, whereas gene(s) in 11q23 may be important in the neoplastic process in a less cell-type specific manner and perhaps particularly vulnerable to neoplastic rearrangement in fetal life. The finding of four cases out of 34 with translocations between 11q23 and chromosome 19 indicates that this rearrangement might characterize a specific cytogenetic subgroup of leukemia in the very young.