OBJECTIVEBone marrow megakaryocytes overly proliferate and abnormally develop among patients with idiopathic thrombocytopenic purpura (ITP). Previous studies showed that it resulted from the abnormal immune function of the body. But the changes in megakaryocytes, especially in micromegakaryocytes in this disease are unclear. The present study was designed to explore the growth and development status of megakaryocytes and the significance of changes in micromegakaryocytes in pediatric cases.

METHODSRoutine bone marrow smears assay and enzyme labeling for micromegakaryocytes with CD41 monoclonal antibody (McAb) were performed in 46 children with ITP. The level of platelet-associated immunoglobulin (PA-Ig) was measured with ELISA.

RESULTSAmong 46 children, 36 had acute ITP (AITP)and 10 chronic ITP (CITP). The number of megakaryocytes increased or was normal in 45 patients, but decreased only in 1 case of CITP. The positive rate of micromegakaryocytes and type I micromegakaryocytes was 98% (45/46) and 35% (16/46), respectively. The positive rate of type I micromegakaryocytes was higher in CITP (50%) cases than that in AITP (31%) cases, but the median of the other three types of micromegakaryocytes in CITP cases (159) was lower than that in the AITP cases (336). There was no relationship between the numbre of all types of megakaryocytes and the level of PA-Ig.

CONCLUSIONMajority of patients with ITP showed an increase in micromegakaryocytes, especially in type II, III and IV. The immune disturbance might not be the only reason for ITP. The abnormality of quality of megakaryocytes might be one of the potential causes for thrombocytopenia in some cases of ITP, especially in those of CITP. The appearance and the number of type I micromegakaryocytes might reflect the prognosis of cases of ITP.