What is the primary hemostatic complication of essential thrombocythemia (ET)?

Primary Hemostatic Complications of Essential Thrombocythemia

The primary hemostatic complication of essential thrombocythemia (ET) is thrombotic events, which represent the major cause of morbidity and mortality in these patients. 1

Thrombotic Complications

Thrombotic events are the most significant hemostatic complications in ET patients, occurring in both arterial and venous circulation:

• Arterial thrombosis: More common than venous events, including stroke, TIA, myocardial infarction, and peripheral arterial occlusion 1
• Venous thrombosis: Including deep vein thrombosis, pulmonary embolism, portal vein thrombosis, and unusual site thrombosis like Budd-Chiari syndrome 1
• Microvascular disturbances: Erythromelalgia, headaches, visual disturbances, and chest pain 1

Risk Factors for Thrombosis

The risk of thrombosis in ET is determined by several factors:

• Age >60 years: Major risk factor 1
• Prior history of thrombosis: Strongest predictor of recurrent events 1
• JAK2V617F mutation: Associated with increased thrombotic risk 1
• Cardiovascular risk factors: Hypertension, diabetes, smoking 1
• Leukocytosis >11 × 10^9/L: Associated with increased arterial thrombotic risk 1

Hemorrhagic Complications

While less common than thrombotic events, hemorrhagic complications can occur in ET patients:

• Primarily affects patients with extreme thrombocytosis (>1,000/μL) 2
• Most commonly manifests as gastrointestinal bleeding 3
• Associated with acquired von Willebrand disease (VWD) in patients with very high platelet counts 1

Abnormal Platelet Function

Platelets in ET patients often demonstrate functional abnormalities:

• Morphological alterations including anisocytosis and giant platelets 4
• Paradoxical prolonged closure time on platelet function analysis despite thrombotic tendency 4
• Altered platelet-endothelial interactions 4
• Abnormal platelet activation and aggregation responses 5

Risk Stratification and Management

Management of ET is based on risk stratification:

High-Risk Patients

• Age >60 years and/or history of thrombosis
• Treatment: Cytoreductive therapy (hydroxyurea, interferon, or anagrelide) plus low-dose aspirin 1
• Monitor for new thrombosis, acquired VWD, and disease-related bleeding 1

Low-Risk Patients

• Age <60 years without history of thrombosis
• Treatment: Low-dose aspirin alone may be sufficient unless contraindicated 5
• Observation may be preferred over aspirin in patients with platelet counts >1,000×10^9/L or CALR mutations 5

Important Clinical Considerations

• Platelet count alone is not a reliable predictor of thrombotic risk, as complications can occur even at relatively low platelet counts 2
• Twice-daily aspirin administration may be more effective than once-daily dosing in preventing thrombotic events in ET patients 5
• Symptomatic or progressive splenomegaly is an indication for cytoreductive therapy even in otherwise low-risk patients 6
• Patients with a positive history of thrombosis are at high risk (40.6% recurrence rate) and should receive cytoreductive and anti-platelet treatment 3

Answer to Multiple Choice Question

The answer is B. thrombotic. While ET patients may experience all three complications (thrombotic events, hemorrhagic complications, and abnormal platelet function), thrombotic events represent the primary and most clinically significant hemostatic complication, causing the greatest morbidity and mortality in these patients.