Abstract : In this study, we report on a family with a germline JAK2 G571S mutation with only one individual presenting with thrombocytosis, who also had a somatic CALR mutation (insertion p.K385fs*47). Our results highlight the complexity of the diagnosis of chronic thrombocytosis, and confirm that genetic alterations in the JAK2 and CALR genes are not always mutually exclusive, nor always responsible for disease phenotype. Our findings suggest that, in routine clinical practice, the diagnostic workup of patients with thrombocytosis should include the simultaneous investigation of JAK2, CALR, and MPL mutations (ie, should not stop once a mutation is identified in the JAK2 gene).
