Chronic myeloid leukaemia with extreme thrombocytosis at presentation: Incidence, clinical findings and outcome

Chronic myeloid leukaemia (CML) usually presents with marked leucocytosis, but rare cases may present with an isolated, marked thrombocytosis, defined as a platelet count >1000 × 109/l (Turakhia et al, 2016). The natural history and the optimal treatment of this entity are not well characterized. We have previously reported our monocentric experience (Sorà et al, 2014); based on these results, we evaluated the incidence, clinical characteristics and outcome of this CML variant in a large series of patients from 16 different Italian haematological centres. From January 2002 to December 2015, 87 of 1591 patients with extreme thrombocytosis were identified, with an estimated incidence of 5·5%. Patient characteristics are shown in Table 1. Coagulation tests were available in 59/87 patients (67·8%), of which only three (5%) had an abnormally prolonged activated partial thromboplastin time. These three patients were investigated for the presence of a non-specific inhibitor, such as antiphospholipid antibodies, and the levels of coagulation factors. In one patient, anti-cardiolipin antibodies were also detected and in another patient a protein C deficiency was identified. However, only a few patients had undergone a full investigation for congenital thrombophilia, including F2 (prothrombin) G20210A mutation and F5 R506Q (Factor V Leiden).