Objective: In recent years, it became necessary to identify a new clinical form of polycythemia vera – latent polycythemia vera (LPV). Considering the significant role of the JAK2V617F gene in the pathogenesis of LPV, we investigated the relationship between the allele burden of the JAK2V617F gene and clinical and laboratory parameters of the disease.
Case report: Patient G.N., at the age of 64, complained of pain in the legs, itching during bathing, weakness, headaches. He had been ill for several years. He suffered from glaucoma, as a result of which he acquired blindness. For a long period paresthesias, erythromelalgia and a gradual impairment of movement in the lower extremities had been observed. The patient was observed by a neurologist with a diagnosis of sensory neuropathy. Recently pain in the legs intensified and there were difficulties in walking. Due to changes in the hemogram, the patient was sent for a consultation to a hematologist. During examination, hyperemia on the face, traces of scratching were visible on the skin. On palpation, the spleen was enlarged by 1.5cm. In laboratory analysis in the hemogram Hb-185g/L, RBC-6.96×1012/L, Ht-58.5%, WBC-13.4×109/L, PLT-471×109/L. Taking into account the clinical and laboratory data, the patient underwent trepanobiopsy and molecular genetic analysis for the JAK2V617F mutation. As a result of histological examination of the trepanobioptate, three-branch proliferation in the bone marrow was revealed. The allele burden of the JAK2V617F gene was 79.5%. The patient was diagnosed with PV. After phlebotomy 4 times at a dose of 500ml+LDA, the patient's condition improved, the pain in the legs disappeared, and independent movement without the help resumed. Control parameters of the hemogram: Hb-131q/L, RBC-4.5×1012/L, Ht-40%, WBC-9.69×109/L, PLT-394×109/L.
Methodology: The data of 193 patients were analyzed: hemogram parameters, allele burden of the JAK2V617F gene, analysis of the risk groups of patients were carried out. The WHO classification of 2008 and 2016, the prognosis of the risk of thrombohemorrhagic complications (TC) according to the Marchioli scale was used.
Results: Out of 193 patients, 127 were with classic polycythemia vera (CPV), and 66 were with LPV. The age of the patients (M±m) with CPV was 57.01±1.1 years, with LPV – 55.03±1.6 years (p>0.05). 97% of patients had the mutation of JAK2V617F gene. Laboratory parameters of patients with CPV and LPV were compared (M±m): hemoglobin – 182.66±2.1g/L and 157.97±2.2g/L (p<0.05), hematocrit – 71.85±1.4% and 63.5±1.8% (p<0.05), erythrocytes – 6.18±0.1×1012/L and 5.46±0.1×1012/L (p<0.05), platelets – 526.85±30.9×109/L and 429.3±34.7×109/L (p<0.05), leukocytes 11.92±0.6×109/L and 10.79±0.7×109/L (p>0.05), allele burden of the JAK2V617F gene – 55.0±6.4% and 27.0±6.9% (p<0.05). Allele burden was divided into quartiles. In CPV 21.78% of patients belonged to the 1st, 20.16% to the 2nd, 18.55% to the 3rd, 39.51% to the 4th quartile. In LPV – 20% of patients belonged to the 1st, 80% to the 2nd quartile, in the 3rd and 4th quartiles there were no patients. In CPV the highest leukocyte count was in the 4th quartile. In LPV patients with an allele burden of the JAK2V617F gene above 40% had higher leukocyte and platelet counts, while the allele burden did not exceed 50%. We did not find any more relationship between allele burden and other hemogram parameters in patients with CPV and LPV. TC risk groups in CPV-low – 56.34%, intermediate – 38.03%, high – 5.63%, in LPV- low – 51.3%, intermediate –16.2%, high – 32.5%. In the analysis of JAK2V617F gene allele burden in the 1st and 2nd quartiles, no differences were found between the risk groups of LPV patients.
Conclusion: Out of PV patients 65.8% were with CPV, and 34.2% with LPV. In LPV the allele burden was lower than in CPV and did not exceed 50%. In CPV and LPV more than 51% of patients were at low risk of TC. CPV patients with JAK2V617F allele burden >75% had higher leukocyte count. LPV patients with JAK2V617F allele burden >40% had higher leukocyte and platelet counts.
