| Research Abstract |
Ultrastructural and ultracytochemical sturies were performed on blasts from 15 Down's syndrome neonates with transient myeloproliferative disorder (TMD). And 12 of them with precise immunological and clinical data were compared with 13 Down's syndrome patients with megakaryoblastic leukemia (MKL) in order to clarify the cytological nature of the blast cells. Average platelet peroxidase-positivity in blast cells of TMD were similar to those of MKL. Blast cells from TMD contained alpha granules, myeloperoxidase-positive granules, electron lucent granules, granules with membrane components, basophil-like granules and granules with ferritin particles. Blast cells from MKL with down's syndrome contained electron lucent granules, granules with membrane components and a few basophil granules, but lacked alpha granules, MPO-positive granules and granules with ferritin particles. A demarcation membrane system was observed in blasts from TMD, but not in MKL with Down's syndrome.
These findings suggest that blast cells in TMD show differentiation to megakaryocytes, neutrophils, basophils, and erythroblasts, while blast cells from MKL show limited differentiation to immature megakaryocytes, erythroblasts and a few basophils. And these results coinside with culture studies which showed differentiation of TMD blasts to various types of blood cells.
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