[Diagnosis of latent polycythemia vera: A clinician's opinion]

to identify the clinical features of latent polycythemia vera (PV) as an independent nosological entity.

The investigation enrolled 81 patients (50 with extensive (manifest) PV and 31 with latent PV) who had visited the Outpatient Department, Hematology Research Center, Ministry of Health of Russia, in 2014 to October 2015.

The gender distribution of the patients was statistically comparable in the analyzed groups. The patients with manifest PV were slightly older than those with latent PV: the median age in the compared groups was 56 and 44 years, respectively. Red blood cell counts, hemoglobin concentrations, and packed cell volume were higher in the patients with manifest PV. Blood platelet counts were higher in the latent PV group. There were no differences in the number of white blood cells in the compared groups. All the patients were JAK2 V617F mutation carriers. The JAK2 allele load was significantly higher in the manifest PV group than in the latent PV group. The compared patient groups differed in the rate of thromboses in the history or at diagnosis. In the patients with latent PV, thromboses were detected in 38% of cases versus 16% in those with manifest PV. In latent PV, there were mainly venous thromboses; abdominal vascular thromboses were diagnosed with a high frequency. Arterial thromboses were revealed in only 2 cases.

Chronic myeloproliferative disease that is characterized by the JAK2 V617F mutation, borderline hemoglobin counts, and morphological features of a bone marrow trephine biopsy specimen, which are specific for PV, is an independent PV variant, namely: latent PV.