CALR and essential thrombocythemia: However, as already suggested13, CALR-mutated ET show clinical features different from JAKV617F-positive ET and might be considered as a distinct disease entity from JAK2V617F-positive ET; in fact, CALR-mutated ET patients present a higher PLT count coupled with a lower thrombotic risk if compared to JAK2V617F-positive ET patients10,13,14.