JAK 2 EXON 12 MUTATION DETECTION

JAK2 GENE MUTATIONS ARE IMPORTANT DIAGNOSTIC MARKERS FOR THE MYELOPROLIFERATIVE DISORDER POLYCYTHEMIA VERA (PV). A SINGLE MUTATION (V617F) IS FOUND IN APPROXIMATELY 95% OF CASES. OF THE PV CASES THAT ARE V617F-NEGATIVE (APPROXIMATELY 5%), MOST ARE ASSOCIATED WITH MUTATIONS IN A DIFFERENT REGION OF THE JAK2 GENE WITHIN EXON 12. PATIENTS WITH EXON 12 MUTATIONS PRESENT FREQUENTLY WITH ERYTHROCYTOSIS AS THE PREDOMINANT FEATURE, BUT WITHOUT CONCURRENT ELEVATIONS IN THE MEGAKARYOCYTIC OR GRANULOCYTIC LINEAGES AS SEEN IN V617F-POSITIVE PV. CONSEQUENTLY, MANY EXON 12 POSITIVE CASES ARE CONSIDERED CLINICALLY AS IDIOPATHIC ERYTHROCYTOSIS. UNLIKE THE V617F MUTATION THAT IS FOUND IN SEVERAL MYELOPROLIFERATIVE NEOPLASMS (PV, ESSENTIAL THROMBOCYTHEMIA & PRIMARY MYELOFIBROSIS), JAK2 EXON 12 MUTATIONS ARE RESTRICTED ONLY TO CASES OF PV. WHO (2016) DIAGNOSTIC ALGORITHM FOR SUSPECTED PV NOW RECOMMENDS JAK2 EXON 12 MUTATION SCREENING IN PATIENTS WHO PRESENT WITH A SUSPICION FOR PV THAT IS V617F NEGATIVE.