Caractéristiques clinico-biologiques des patients avec thrombocytémie essentielle en fonction de leur statut mutationnel JAK2 ou CALR : étude monocentrique de 40 patients et revue de la littérature

Background

Somatic 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.

Methods

We 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.

Results

Among 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 52 bp deletion and 5 bp 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.

Conclusion

JAK2 and CALR mutation screening in ET has a diagnostic value. Each mutation displays a distinct phenotype with uncertain impact on long-term outcome.