JAK2 Exon 12 mutations

Besides the more common V617F mutation that resides in the exon 14 of JAK2, mutations have subsequently been described in the exon 12 of JAK2. These mutations are found in the rare Polycythemia Vera patients who do not have the V617F mutation. As in other PV cases, patients with JAK2 exon 12 mutations have low serum erythropoietin levels and most often, positive endogenous erythroid colony formation. A “pure erythroid” phenotype is characteristic of JAK2 exon 12 mutations although thrombocytosis or hyperleukocytosis can be found. In contrast to JAK2V617F which always affect the same base (G1849), always mutated for a T, JAK2 exon 12 mutations are far more diverse and can either consist of point mutations, deletions, insertions or any kind of combination of the above. This particularity combined with the fact that JAK2 exon 12 mutant allelic burden can be low make their detection difficult. Several techniques have been described, none of which being entirely satisfactory, which explains that most laboratories run several techniques in parallel for their detection. Click here to get a table listing the main laboratories members of our network that offer JAK2 exon 12 mutation screening, and the technique(s) used. These laboratories can be contacted either to arrange for sending samples or to give help to set-up techniques.