Abnormal blood cell counts are characteristic of patients with Down syndrome and transient abnormal myelopoiesis (TAM). Although some patients with TAM experience prolonged anemia or thrombocytopenia, hematological factors predicting blood cell count recovery have not been reported yet. The aim of this study was to investigate the factors influencing platelet normalization in TAM.
A retrospective review of the medical records of 21 patients with TAM admitted to the neonatal intensive care unit at Kanagawa Children’s Medical Center between January 2007 and October 2014 was undertaken.
In the 16 patients (76%) experiencing transient thrombocytopenia, a large number of blasts at diagnosis was found to be significantly associated with late platelet recovery (R=0.669, p<0.05), and higher platelet counts at diagnosis were significantly associated with later recovery (R=0.719, p<0.01). Indeed, a strong positive correlation between blast and platelet counts at diagnosis was found (R=0.730, p<0.01).
Our data suggest that high platelet counts at TAM diagnosis might reflect abnormal thrombocyte production from blasts. Thus, physicians should be aware of the possibility of prolonged thrombocytopenia in patients with TAM who exhibit a high platelet and/or blast count at diagnosis.

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