Transient myeloproliferative disorder and eosinophilic pericardial effusion in a down syndrome neonate

□ Transient myeloproliferative disorder seen in neonates with Down syndrome is often thought to have a benign course. The authors describe the clinical and laboratory profile of a neonate with Down phenotype and transient myeloproliferative disorder with pericardial effusion as co-morbidity. Pericardial fluid analysis showed eosinophils. Pericardial effusion resolved with prednisolone therapy. Regression in hepatosplenomegaly with clearance of blasts was seen by third week of illness. The clinical course suggested a benign infiltration of the pericardium. Presence of eosinophils supports the differentiating capability of the blast cells in transient myeloproliferative disorders.