Thrombocytosis in myelodysplastic and myelodysplastic/myeloproliferative syndromes.

Thrombocytosis at diagnosis is uncommon in myelodysplastic (MDS) and myelodysplastic/myeloproliferative (MDS/MPD) syndromes. We conducted a retrospective analysis to determine the clinical and haematopathological features of such patients, and the effect of thrombocytosis on prognosis. Of the 388 patients diagnosed with MDS from 1980 - 2006, 31 presented with thrombocytosis. The majority (71%) had low risk features and a low incidence of spontaneous bleeding or thrombo-embolic events. Compared to a case-matched control group of MDS and MDS/MPD patients without thrombocytosis of similar ages and IPSS scores, patients with thrombocytosis had a slightly lower probability of progression to a higher grade of MDS (P = 0.03), equivalent risk of transformation to acute myeloid leukemia (AML), and a trend (P = 0.07) towards longer overall survival (median 35.4 months compared to 27.6 months for controls).