Preleukemic syndrome in children. Report of four cases and review of literature.

Childhood preleukemia, known as a rare condition, was evaluated in four of the authors' cases and in 24 cases from the literature. The required condition was evolution into overt acute leukemia. The children were 5 months to 15 years of age, and the preleukemia period ranged from 2 to 42 months. The symptoms and physical signs were nonspecific. Different kinds of cytopenia were found in the peripheral blood. Twelve children developed ALL and 16 developed AML. The analysis revealed that in childhood there exist two different types of preleukemia: pre-ALL and pre-AML. The age and sex distribution were different, as were the hematological changes. The marrow was usually hypoplastic in pre-ALL but hyperplastic in pre-AML. True hypoplasia in any of the three cell lines was more common in pre-ALL, whereas ineffective thrombopoiesis and normal or increased myelopoiesis were specific for pre-AML. Ineffective erythropoiesis was characteristic of both types. A typical chromosomal change in marrow, seen in pre-AML only, was a missing group C chromosome. The childhood pre-AML resembled adult preleukemia (also pre-AML) in many aspects, whereas the childhood pre-ALL seemed to be a different entity. It might be assumed that all preleukemic conditions do not evolve to overt malignancy. The incidence and true prognosis therefore remain unknown.