Acute leukemia in infants. A unique pattern of acute nonlymphocytic leukemia.

At present, the majority of children with acute lymphoblastic leukemia can expect a favorable outcome. However, leukemia in infants (0-1 year) still runs a dismal course. The first year of life also has a unique pattern of hematopoietic activity. We investigated possible association between these two findings. We examined the characteristics of 51 infants with leukemia, diagnosed from 1975 to 1984; 48/51 had evaluable data. Infants had a high frequency (39.6%) of hyperleukocytosis (greater than 100 X 10(9)/liter), early central nervous system involvement (27.1%), and cutaneous infiltration (18.8%). The respective numbers in patients greater than or equal to 1 year were 13.9, 4.8, and 1.0%. Acute nonlymphocytic leukemia was diagnosed in 18/48 infants (37.5%) compared to 128/892 (14.3%) in older patients. Infants had only acute leukemia of French-American-British (FAB) class M5 (10/19) or acute leukemia with unclassifiable but monocytoid blasts (8/19). This study confirms the presence of poor prognostic features in infant leukemia. The almost exclusive occurrence of monoblastic or monocytoid acute leukemia parallels the high proliferation rate of monocytes in this age group and the leukemic cells may thus well reflect frozen stages of monocytic differentiation.