Polycythemia vera

Polycythemia vera
Name	Polycythemia vera
Synonyms	Primary polycythemia; Polycythaemia vera
Specialty	Hematology
Symptoms	Pruritus, erythromelalgia, headache, splenomegaly
Complications	Thrombosis, hemorrhage, myelofibrosis, acute myeloid leukemia
Onset	Middle to late adulthood
Causes	Somatic JAK2 mutations
Diagnosis	Hemoglobin/hematocrit, bone marrow biopsy, JAK2 V617F testing
Treatment	Phlebotomy, hydroxyurea, interferon-alpha, ruxolitinib
Frequency	Rare

Polycythemia vera is a chronic myeloproliferative neoplasm characterized by clonal overproduction of erythrocytes, often with leukocytosis and thrombocytosis, driven most commonly by somatic mutations in the JAK2 gene. It presents with hyperviscosity-related symptoms, splenomegaly, and a risk of thrombotic and hemorrhagic events, and is managed by cytoreductive therapies and phlebotomy to reduce hematocrit. Diagnosis integrates hematologic parameters, molecular testing, and bone marrow assessment to distinguish it from secondary erythrocytosis and other myeloproliferative disorders.

Signs and symptoms

Patients commonly report aquagenic pruritus after bathing and erythromelalgia manifesting as burning pain and erythema of the extremities, while systemic features include headache, dizziness, visual disturbances, and fatigue; these presentations overlap with case reports involving Queen Victoria and clinical descriptions in texts associated with Royal Society of Medicine, Mayo Clinic, Johns Hopkins Hospital, Mount Sinai Hospital. Splenomegaly producing early satiety and left upper quadrant discomfort is frequently documented in literature from Harvard University, University of Oxford, Karolinska Institutet, Stanford University, University of Pennsylvania Health System. Thrombotic events may present as deep vein thrombosis, pulmonary embolism, myocardial infarction, or ischemic stroke, paralleling vascular complications studied by investigators at Cleveland Clinic, Massachusetts General Hospital, University of Cambridge, Imperial College London, Cold Spring Harbor Laboratory. Less common features include gout from hyperuricemia, peptic ulcer bleeding, and portal hypertension noted in series from University of Toronto, Johns Hopkins University School of Medicine, University of California, San Francisco, University of Michigan, University of Sydney.

Pathophysiology

Polycythemia vera arises from clonal hematopoiesis caused predominantly by the somatic JAK2 V617F mutation in hematopoietic stem cells, with additional mutations in genes such as TET2, ASXL1, and DNMT3A reported in cohorts from Broad Institute, Wellcome Trust Sanger Institute, Dana-Farber Cancer Institute, Fred Hutchinson Cancer Center, Institut Curie. Constitutive activation of the JAK-STAT signaling pathway increases proliferation of erythroid, megakaryocytic, and granulocytic lineages, a mechanism explored in studies affiliated with National Institutes of Health, European Molecular Biology Laboratory, Cold Spring Harbor Laboratory, Max Planck Society, Karolinska Institutet. The resultant hyperviscosity alters hemodynamics within cerebral, coronary, and splanchnic beds, contributing to thrombotic risk characterized in analyses by World Health Organization, European LeukemiaNet, American Society of Hematology, International Society of Thrombosis and Haemostasis, Food and Drug Administration. Clonal evolution may progress to post-polycythemic myelofibrosis or transform to acute myeloid leukemia, pathways documented in longitudinal registries from SEER Program, European Cancer Registry, Swedish Cancer Registry, Danish National Patient Registry, Scandinavian Society of Hematology.

Diagnosis

Diagnostic criteria combine elevated hemoglobin or hematocrit thresholds, reduced serum erythropoietin levels, presence of JAK2 V617F or exon 12 mutations, and characteristic trilineage hyperplasia on bone marrow biopsy; these criteria are outlined by panels including World Health Organization, European LeukemiaNet, British Society for Haematology, American Society of Hematology, European Hematology Association. Laboratory assessment includes complete blood count, erythropoietin assay, peripheral smear, and molecular testing performed in reference laboratories at Mayo Clinic Laboratories, Quest Diagnostics, ARUP Laboratories, National Health Service (England), EUROIMMUN AG. Radiologic evaluation with ultrasound or MRI assesses splenic size and abdominal venous thrombosis, as described in guidelines from American College of Radiology, Radiological Society of North America, European Society of Radiology, Society of Nuclear Medicine and Molecular Imaging, British Institute of Radiology. Differential diagnosis requires exclusion of secondary causes such as chronic hypoxia, EPO-producing tumors, and exogenous erythropoietin exposure investigated in case series from Memorial Sloan Kettering Cancer Center, St Bartholomew's Hospital, Karolinska University Hospital, Vanderbilt University Medical Center, University College London.

Management and treatment

Initial management aims to maintain hematocrit below recommended targets using phlebotomy protocols pioneered at centers like Mayo Clinic and Cleveland Clinic, while low-dose aspirin is commonly prescribed for thrombosis prevention following studies by European Collaborative Study Group, International Physicians' Association. Cytoreductive therapy with agents such as hydroxyurea, pegylated interferon-alpha, and the JAK1/2 inhibitor ruxolitinib is used according to risk stratification frameworks from European LeukemiaNet, American Society of Hematology, National Comprehensive Cancer Network, European Society for Medical Oncology, International Myeloproliferative Neoplasms Foundation. Management of pruritus and erythromelalgia includes antihistamines, selective serotonin reuptake inhibitors, and prostacyclin analogs evaluated in trials conducted at Johns Hopkins Medicine, University of Oxford, Institut Pasteur, Mount Sinai Health System, University of Barcelona. Anticoagulation and management of acute thrombosis follow protocols from American College of Cardiology, American Heart Association, European Society of Cardiology, International Society on Thrombosis and Haemostasis, Royal College of Physicians. Enrollment in clinical trials at institutions such as Dana-Farber Cancer Institute, MD Anderson Cancer Center, Fred Hutchinson Cancer Research Center, Cancer Research UK, European Organisation for Research and Treatment of Cancer is recommended for refractory cases.

Prognosis and complications

Long-term outcomes vary; major complications include arterial and venous thrombosis, hemorrhage, progression to myelofibrosis, and leukemic transformation to acute myeloid leukemia, risks quantified in cohorts from SEER Program, Swedish Hematology Registry, Norwegian Hematology Registry, Danish Cancer Society, European Hematology Association. Prognosis improves with effective hematocrit control and thrombosis prevention strategies validated in randomized studies from New England Journal of Medicine, The Lancet, Blood (journal), Journal of Clinical Oncology, Haematologica. Comorbid cardiovascular disease, age, and previous thrombotic events are key prognostic indicators emphasized by guidelines from European Society of Cardiology, American College of Cardiology, World Health Organization, American Heart Association, British Cardiac Society.

Epidemiology and risk factors

Polycythemia vera is rare, with incidence estimates reported by population registries such as SEER Program, European Cancer Registry, Scandinavian Cancer Registries, Canadian Cancer Registry, Australian Institute of Health and Welfare; median age at diagnosis is typically in the sixth decade with a slight male predominance noted in surveillance data from Centers for Disease Control and Prevention, European Centre for Disease Prevention and Control, Public Health England, Health Canada, Australian Bureau of Statistics. Risk is associated with acquired somatic mutations (notably JAK2 V617F) and may be influenced by environmental and occupational exposures explored in epidemiologic studies from International Agency for Research on Cancer, National Toxicology Program, Harvard T.H. Chan School of Public Health, University of Birmingham, Karolinska Institutet. Family clustering and inherited predisposition syndromes have been reported and investigated at genetic centers including Broad Institute, Wellcome Sanger Institute, Genomics England, Institut Curie, McGill University.

Category:Myeloproliferative neoplasms