Transient myeloproliferative disorder. In a neonate with Down syndrome. Immunophenotypic studies

This report describes the results of bone marrow leukocyte immunophenotypic studies, DNA index measurement, and chromosome analysis in a newborn with Down syndrome and transient myeloproliferative disorder. The infant's initial leukocytosis with immature cells in the peripheral blood and thrombocytopenia resolved without treatment by 6 months of age, and he was well at 2 years of age. The lack of specific reactivity between the patient's morphologically immature cells and multiple monoclonal antibodies directed against lymphoid and myeloid leukemia cells may be characteristic of this disorder. Other cases should be examined for immunophenotype to correlate the results with chromosomal analysis and to provide a basis for comparison in those who subsequently develop true acute leukemia.