Megakaryocytic phagocytosis in a chromosomally normal neonate with transient myeloproliferative disorder

The effects of acrylamide on the frequency of megakaryocytic emperipolesis and the mitotic activity of rat bone marrow cells

BACKGROUND

Although the pathophysiological importance of emperipolesis is not known exactly, it has been reported to increase significantly in cases of various cancer types, different tumours and thrombosis disorders. In this study the effects of acrylamide on the frequency of megakaryocytic emperipolesis and the mitotic activity in rat bone marrow cells were determined. For this purpose, two separate experiments were performed with Sprague-Dawley rats gavaged with 0, 30, 45 and 60 mg acrylamide kg⁻¹ body weight (BW) for five consecutive days. In the second experiment, 3 mg colchicine kg⁻¹ BW was injected intraperitoneally 2 h before cervical dislocation. Bone marrow samples were taken 24 h after the last application in both experiments.

RESULTS

It was found that only the highest dose of acrylamide significantly decreased the incidence of megakaryocytic emperipolesis and that the types of bone marrow cells engulfed by megakaryocytes were mostly neutrophil granulocytes. Neither megakaryocytes nor engulfed cells showed any morphological degeneration. In the mitotic activity experiment, doses of 45 and 60 mg acrylamide kg⁻¹ BW decreased the mitotic activity of bone marrow cells in comparison with the control group.

CONCLUSION

It was concluded that the decrease in megakaryocytic emperipolesis frequency might be a consequence of the decrease in mitotic activity in bone marrow cells.

Tetrasomy 21 transient leukemia with a GATA1 mutation in a phenotypically normal trisomy 21 mosaic infant: case report and review of the literature

Infants with constitutional trisomy 21 are at increased risk of developing transient and acute megakaryoblastic leukemia (AMKL). Mutations in GATA1 have been identified in trisomy 21 patients with AMKL, and this lesion is thought to be an initial event by virtue of its presence during transient leukemia. Transient leukemia is also observed in phenotypically normal infants albeit much less commonly so. Almost all these infants are mosaic for trisomy 21, and the clinical course of transient leukemia recapitulates that observed in constitutional trisomy 21. We report a phenotypically normal infant with tetrasomy 21 transient leukemia, GATA1 mutation within exon 2, and trisomy 21 mosaicism restricted to the hematopoietic tissue. Two years after diagnosis, low levels of trisomy 21 persisted in the peripheral blood, which resolved 2.5 years after diagnosis. The GATA1 mutation was not detected at last follow-up. The literature review identified 32 phenotypically normal infants with transient leukemia. Ninety-one percent (29 of 32) were observed and three received chemotherapy at diagnosis of transient leukemia. Nineteen percent (6 of 32) developed acute leukemia, and four continued in remission (two died). Transient leukemia in trisomy 21 mosaicism recapitulates the condition observed in constitutional trisomy 21 at the biological and clinical levels. Infants should be followed for the development of acute leukemia.

Trisomy 21 associated transient neonatal myeloproliferation in the absence of Down's syndrome

Although usually associated with Down's syndrome, transient neonatal myeloproliferation (TMD) can occur in the absence of a constitutional trisomy 21. This report describes two such cases, both of whom had a trisomy 21 restricted to clonal cells. Unlike in previous such reported cases, spontaneous morphological, cytogenetic, and molecular remission in both cases was followed by re-emergence, in one case, of an evolved clone with a more malignant phenotype which required pharmacological intervention. Awareness that trisomy 21 bearing leukaemia in the neonatal period can be transient even in the absence of Down's syndrome is important to prevent unnecessary treatment. Equally, such cases require indefinite follow up as a proportion may have a recurrence which may require treatment.