Relationship of JAK2 (V617F) Allelic Burden with Clinico- Haematological Manifestations of Philadelphia-Negative Myeloproliferative Neoplasms

Allelic burden of Janus kinase 2 in a 6-month course of therapy for myeloproliferative neoplasms

BACKGROUND

Janus kinase 2 (JAK2) V617F gene mutation is an important marker for the diagnosis of Philadelphia negative Myeloproliferative neoplasms (MPN) which is subdivided into Polycythemia Vera (PV), Primary Myelofibrosis (PMF), and Essential Thrombocythemia (ET). The aim here is to investigate the JAK2 allele burden of the patients diagnosed with the subgroups of MPN and to demonstrate the alterations of hematological parameters and spleen size between diagnosis and 6 months of treatment.

METHODS

A total of 107 patients with the diagnosis of MPN and negative Philadelphia chromosome, 51 males and 56 females with a mean age of 59,74 ± 16,41 years, were included in the study. Diagnosis of MPN was based on the World Health Organization (WHO) criteria. Subgroups of MPN distributed as 49,5% ET, 46,7% PV, and 3,8% PMF. Findings such as the age of the patients, JAK-2 allele burden, and laboratory findings of splenomegaly were examined at the time of diagnosis, 3rd month, and 6th month. JAK2 allele burden and spleen size were re-evaluated in 6th month.

RESULTS

Our study confirmed the findings of high Hb, HCT, and RBC but low platelet values in PV patients with high JAK2 allele burden with respect to other groups, a positive correlation between JAK2 allele burden and LDH.

CONCLUSIONS

A novel finding of our study is, that there is not any reducing effect of the phlebotomy on JAK2 allele burden in PV patients whether they receive phlebotomy or not. Evaluation of the spleen size alteration during 6 months within the subgroups demonstrated a decrease in PV and ET groups whereas no statistically significant difference was found in the PMF group.

A Balanced Robertsonian Translocation in a Patient with a Janus Kinase 2-Positive Polycythemia Vera

A male patient with a persistent, combined erythrocytosis, leukocytosis, and thrombocytosis without representative evidence of reactive increase emerged as having a myeloproliferative disorder. Molecular-biological assessment yielded Janus kinase 2-positive results, and the patient was diagnosed with polycythemia vera. In addition to these findings, further karyotyping accounted for a Robertsonian translocation. Because this rearrangement was a balanced variant, we concluded that this cytogenetic result might not significantly alter the diagnosis of polycythemia vera.

Genetic Landscape of Myeloproliferative Neoplasms with an Emphasis on Molecular Diagnostic Laboratory Testing

Chronic myeloproliferative neoplasms (MPNs) are hematopoietic stem cell neoplasms with driver events including the BCR-ABL1 translocation leading to a diagnosis of chronic myeloid leukemia (CML), or somatic mutations in JAK2, CALR, or MPL resulting in Philadelphia-chromosome-negative MPNs with constitutive activation of the JAK-STAT signaling pathway. In the Philadelphia-chromosome-negative MPNs, modern sequencing panels have identified a vast molecular landscape including additional mutations in genes involved in splicing, signal transduction, DNA methylation, and chromatin modification such as ASXL1, SF3B1, SRSF2, and U2AF1. These additional mutations often influence prognosis in MPNs and therefore are increasingly important for risk stratification. This review focuses on the molecular alterations within the WHO classification of MPNs and laboratory testing used for diagnosis.