• M Ben Said, S Gandrille, A M Fischer, and L Darnige.
• Service d'hématologie biologique, hôpital européen Georges-Pompidou, AP-HP, 20, rue Leblanc, 75908 Paris cedex 15, France. Electronic address: mehdi.bsaid@yahoo.fr.
• Pathol. Biol. 2015 Jun 1; 63 (3): 117-21.

BackgroundSomatic mutations in the calreticulin gene (CALR) were recently described in essential thrombocythemia (ET) and primary myelofibrosis with non-mutated JAK2 or MPL. The aim of this single-center study was to compare the clinical and biological features of ET patients according to their mutational status.MethodsWe included 40 patients with ET followed in hematology consultation. The JAK2 V617F mutation was assessed by quantitative PCR. For the detection of CALR mutations, we performed a PCR amplification of CALR exon 9 followed by direct sequencing.ResultsAmong 40 study patients, 23 (57.5%) harbored V617F JAK2, 12 of the 17 patients without JAK2 mutation harbored CALR, no patient expressed MPL mutation and 5 were negative for all three mutations. Five types of mutations were identified with predominance of 52bp deletion and 5bp insertion (7/12 and 2/12 respectively). The incidence of thrombotic events at diagnosis was significantly higher in JAK2 mutated patients (P<0.05). Biologically, patients with CALR mutation had significantly higher platelet count (P<0.01) and significantly lower hemoglobin level (P<0.05) than those with V617F JAK2 mutation.ConclusionJAK2 and CALR mutation screening in ET has a diagnostic value. Each mutation displays a distinct phenotype with uncertain impact on long-term outcome.Copyright © 2015 Elsevier Masson SAS. All rights reserved.

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