Detection of Exon 12 and 14 Mutations in Janus Kinase 2 Gene Including a Novel Mutant in V617F Negative Polycythemia Vera Patients from Pakistan

Abstract

The most frequently reported genetic aberration among polycythemia vera (PV) patients is a gain of function mutation V617F in exon 14 of Janus kinase 2 (JAK2) gene. However in many investigations, V617F negative PV patients have been reported to harbor mutations in JAK 2 exon 12. We investigated 24 patients with PV (diagnosed following 2016 WHO guidelines) to detect V617F mutation through allele specific PCR. The frequency of which was found to be 19/24 (79.2 %). Later on JAK2 exon 12 and 14 was amplified by conventional PCR in V617F negative patients and subjected to sequence analysis. A total of 03 mutated sites in exon 12 were detected in only two V617F-negative patients 2/5 (40%). All three substitutions were heterozygous i.e. F537F/I found in both patients and R528R/T, which is a novel mutation. In addition, one patient 1/5 (10%) manifested amino acid substitution V617A in JAK2 exon 14. Hematological parameters of individuals harboring mutations do not vary significantly than rest of the PV patients. Previous history and 2.3 years of follow-up studies reveal 15-year survival of V617F positive patients (n=19) to be 76%, while it is 94% for wild type V617 patients (n=05). Mean TLC of the patient cohort was 17.6± 9.1 x 109/L, mean platelet count was 552± 253 x 109/L, mean hemoglobin was 16.9± 3.2 g/dl, mean corpuscular volume (MCV) was 77.2± 13.0 fl and mean corpuscular hemoglobin (MCH) was 25.6± 3.9 pg. This is the very first attempt from Pakistan to screen JAK2-exon 12 mutations in PV patients. We further aim to investigate Jak2 exon 12 mutations in larger number of PV patients to assess their clinical relevance and role in disease onset, progression and transformation.

Masked Polycythemia Vera and Iron Deficiency in a Fertile-Age Woman

“…This has diagnostic implications, as Hb and Htc levels cannot reach the defined PV diagnostic threshold, blurring the clinical picture and delaying a targeted investigation. This subset of patients has a masked PV, for which diagnosis is challenging [1][2][3][4][5].…”

“…The World Health Organization (WHO) and the British Society for Hematology updated the classification for myeloproliferative neoplasms (including PV) in 2016 and 2018, respectively [ 2 , 3 ]. According to the WHO guidelines, the diagnosis is now based on three major criteria: elevated Hb (> 16.5 g/dL in men and > 16 g/dL in women) or Htc levels (> 49% in men and > 48% in women) or increased RBC mass (> 25% above mean normal predicted value); bone marrow biopsy (BMB) with features of PV (hypercellularity for age, panmyelosis, and prominent erythroid growth); the presence of Janus kinase 2 (JAK2) V617F mutation (exon 14) or JAK2 exon 12 mutation (which together accounts for 98% of cases) [ 4 , 5 ]. Decreased serum erythropoietin level was introduced as a minor criterion for diagnosis when the first two major ones are verified [ 2 ].…”

“…Patients can experience symptoms such as aquagenic pruritus, fatigue, dizziness, nausea, upper abdominal discomfort, weakness, and peripheral paresthesia, which are not easily attributable to a single cause. PV is also associated with hyperviscosity, thrombosis, and bleeding, as well as a potential for progression to myelofibrosis and acute leukemia (blast phase) in about 20% of patients [ 5 ]. BMB is not mandatory for diagnosis but is the only exam to identify or predict progression [ 2 , 5 ].…”

“…PV is also associated with hyperviscosity, thrombosis, and bleeding, as well as a potential for progression to myelofibrosis and acute leukemia (blast phase) in about 20% of patients [ 5 ]. BMB is not mandatory for diagnosis but is the only exam to identify or predict progression [ 2 , 5 ].…”