Figure 1.

Diagram showing three independent actions of hydroxycarbamide which are potentially of therapeutic benefit in preventing vaso-occlusion and vasculopathy. Most evidence exists for hydroxycarbamide’s action on erythroid cells (thick arrow), while observational studies have suggested that the reduced neutrophil count is also of therapeutic benefit (thin arrow). Laurance et al. in this issue showed in vitro evidence of hydroxycarbamide altering adhesion molecule expression in the vascular endothelium¹⁷ (dotted arrow) although the clinical significance of this is not yet known.