What other parameters are seen in polycythemia vera?

Parameters Seen in Polycythemia Vera

Polycythemia vera (PV) is characterized by multiple hematological and clinical parameters beyond elevated red blood cell mass, including leukocytosis, thrombocytosis, splenomegaly, and specific laboratory markers like JAK2 mutations and low serum erythropoietin levels.

Hematological Parameters

Blood Cell Abnormalities

• Erythrocytosis: Elevated hemoglobin (>16.5 g/dL in men, >16.0 g/dL in women) and hematocrit (>49% in men, >48% in women) 1, 2
• Thrombocytosis: Present in approximately 53% of patients 2
• Leukocytosis: Present in approximately 49% of patients 2
• Panmyelosis: Bone marrow showing prominent erythroid and megakaryocytic proliferation 3

Molecular Markers

• JAK2 mutations: Present in >95% of PV patients 1, 4
  • JAK2V617F (exon 14) mutation in most cases
  • Exon 12 JAK2 mutations in some cases 3
• Additional mutations: Over 50% of patients harbor mutations beyond JAK2 5
  • TET2 (18%)
  • ASXL1 (15%)
  • Prognostically adverse mutations: SRSF2, IDH2, RUNX1, and U2AF1 (combined 5-10%)

Laboratory Findings

• Low serum erythropoietin levels: Characteristic finding in PV 3, 1
• Endogenous erythroid colony formation: Growth of erythroid colonies without exogenous erythropoietin 3
• Abnormal karyotype: Present in 15-20% of patients 5
  • Most common abnormalities: +9 (5%), loss of Y chromosome (4%), +8 (3%), and 20q- (3%)

Clinical Parameters

Physical Findings

• Splenomegaly: Present in approximately 36% of patients 2
• Hepatomegaly: May be present in some cases 3
• Plethora: Ruddy complexion due to increased red cell mass 3

Vascular Complications

• Arterial thrombosis: Present in 16% of patients at or before diagnosis 2
• Venous thrombosis: Present in 7% of patients at or before diagnosis, often in unusual sites like splanchnic veins 2, 6
• Microvascular disturbances: Including erythromelalgia (5.3%) 1, 2
• Bleeding tendency: Especially in patients with acquired von Willebrand disease associated with extreme thrombocytosis (≥1000 × 10^9/L) 2

Symptomatic Manifestations

• Pruritus: Affects approximately 33-48% of patients, often aquagenic (water-induced) 1, 2
• Constitutional symptoms: Fatigue, night sweats, weight loss 7
• Erythromelalgia: Burning pain and redness in extremities 1
• Visual disturbances: Transient visual changes in 14% of patients 2
• Abdominal discomfort: Often related to splenomegaly 2

Disease Progression Parameters

• Risk of transformation to myelofibrosis: Approximately 16% at 20 years 6, 5
• Risk of transformation to acute myeloid leukemia: Approximately 4% at 20 years 6, 5
• Thrombotic risk: Approximately 26% at 20 years 6, 5

Risk Stratification Parameters

• Age >60 years: Major risk factor for thrombosis 1, 6
• History of thrombosis: Major risk factor for recurrent thrombosis 1, 6
• Leukocytosis: Associated with worse survival and increased thrombotic risk 5
• Cardiovascular risk factors: Particularly hypertension and smoking 7
• JAK2V617F allele burden: Higher burden associated with increased venous thrombosis risk 5

Understanding these multiple parameters is essential for accurate diagnosis, risk stratification, and management of polycythemia vera, distinguishing it from secondary causes of polycythemia and guiding appropriate therapeutic interventions.