OBJECTIVEThrombocytopenic hemorrhage is one of the major appearance in pediatric hemorrhagic diseases, in which, idiopathic thrombocytopenic purpura (ITP) is the most common disease. Thrombocytopenia is the earliest phenomenon or the only one in certain phases of hemorrhagic diseases, such as ITP, aplastic anemia (AA) and myelodysplastic syndrome (MDS). By now, the pathogenesis of thrombocytopenia in different diseases has not been clearly determined. At present, it is very difficult to diagnose these diseases and estimate their prognosis with current clinical data. In this study, morphological characteristics and hematopoiesis function of bone marrow megakaryocyte in pediatric patients with ITP, AA and MDS were observed and the cause and mechanism of different thrombocytopenias were analyzed.

METHODSThere were 16 children with ITP, 17 with AA and 16 with MDS in this study. CD41 McAb immunohistochemical technique was used to detect micromegakaryocyte on bone marrow smears. Plasma clot culture and CD41 McAb immunohistochemical technique were used for the MK-colony forming assay. The colony formation rate of colony formation unit-megakaryocyte (CFU-MK) and burst formation unit-megakaryocyte (BFU-MK) were counted.

RESULTSThere was no statistical difference on the positive rates of micromegakaryocyte and type I lymphoid small micromegakaryocyte between groups of ITP and control. The number of micromegakaryocyte and the formation rates of CFU-MK in ITP group were significantly higher than those in control group. Among AA patients, the numbers of MK, micromegakaryocyte and the formation rates of CFU-MK, BFU-MK in vitro significantly decreased. There was no significant difference in the positive rate of micromegakaryocyte between groups of MDS and control, but the number of micromegakaryocyte and the positive rate of type I lymphoid micromegakaryocyte were significantly higher than those of control group. There was no statistical difference of the formation rate of CFU-MK between groups of MDS and control. But in 63% childhood patients, the formation rate of CFU-MK decreased, 25% increased,and 13% was normal; BFU-MK formation rate decreased significantly in MDS group.

CONCLUSIONOverproliferation of bone MKs may exist in most ITP patients. For obviating the nosogenetic factors, the normal MK releasing platelet could be easily found in the culture system. But the colony formation rate of MK decreased in a few patients with CITP. The abnormality of MK might be one of the reasons for thrombocytopenia in partial patients with ITP. Underproliferation of MKs may exist in AA, but no pathosishemogenesis was found. The dysfunction of early phase MK progenitor and stem cell might be the major reason for AA, but not the abnormality of hematopoietic microenvironment. There may be two kinds of megakaryocyte clones in bone marrow of children with MDS. One may be pathologic and potentially malignant micromegakaryocytes, the other may be the normal megakaryocytic precursors. The increase of pathologic MK resulted in abnormal development and maturation of MK in bone marrow. The change of megakaryopoiesis showed different in ITP, AA or MDS. Using bone marrow smear megakaryocyte counting, small micromegakaryocyte immunohistochemical detecting and the formation rate of bone marrow MK colony assay, the different thrombocytopenia can be diagnosed during the early stage of ITP, AA or MDS.