[Transient myeloproliferative disorder (TMD) with transiently increased tetrasomy-21 cells in a phenotypically normal...

We reported a case of TMD with transient increase of tetrasomy-21 cells in a phenotypically normal newborn. The patient was admitted to the St. Marianna University Hospital due to hepatosplenomegaly on the 7th days after birth. Hematological findings on admission revealed remarkable leukocytosis (168,300/microliters) with 79% blasts. Immunological studies of the blasts showed a positive reaction for platelet associated antigens, KOR-P77, AN50, TP80 and a pan-T antigen, TP40. Cytochemically blasts were strongly positive for acid phosphatase, positive for alpha NAE and weakly positive for PAS. The platelet peroxidase reaction was observed in rough endoplasmic reticulum of blast cells. Both immunological and cytochemical findings suggested that the blasts were of megakaryocyte lineage. Chromosomal analysis of the blasts showed 48, XX, + 21, +21 (21 tetrasomy). After chemotherapy with PSL and 6MP, bone marrow showed a complete remission. But we thought it was spontaneous remission because PSL and 6MP were not effective to acute megakaryocytic leukemia (AMKL). Bone marrow cells were karyotypically normal on the 67th day of life when abnormal blasts were not observed in the bone marrow.