Transient Myeloproliferative Disorder In a Neonate with Down Syndrome

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 periph-eral 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. A RARE, SELF-LIMITED DISORDER simulat-ing leukemia may occur in newborns with Down syn-drome,1-5 including those with chromosomal mosaic-ism.6-9 This condition, which must be differentiated from true congenital leukemia, has also been called &dquo;transient congenital leukemia&dquo; and &dquo;acute transien