Hypoplastic myelodysplastic syndromes can be distinguished from acquired aplastic anaemia by bone marrow stem cell expression of the tumour necrosis factor receptor

Summary. It is often difficult to distinguish hypoplastic myelodysplastic syndrome (h-MDS) from acquired aplastic anaemia (AA), because of the considerable clinical, cytological and histological similarities between these two disorders. The distinction between AA and h-MDS is important because there is a higher risk of progression to acute leukaemia in patients with h-MDS compared with AA. Recent studies suggest that tumour necrosis factor-alpha (TNF-α) plays an important role in the development of AA. In order to determine the potential importance of TNF-α in the differential diagnosis of hypoplastic bone marrow (BM) disorders, we examined whether analysis ofTNF-receptor expression could be used as a tool to differentiate AA from h-MDS. Flow cytometric analysis revealed that BM stem cells (CD34+) from AA patients have markedly greater TNF receptor (R) 1 and TNFR2 expression than those from patients with MDS and h-MDS. We suggest that the BM stem cells with a high expression of TNFR in patients with AA may be potently sensitive to TNF-α stimulation of differentiation. Thus, we propose that quantification of TNFR expression in BM stem cellsmay be a useful method to distinguish AA from h-MDS.