Unmasking Essential Thrombocythemia in Heparin-Induced Thrombocytopenia After Coronary Artery Bypass Grafting

Heparin-induced thrombocytopenia (HIT) and JAK2 V617F-positive essential thrombocythemia (ET) are prothrombotic conditions that complicate postoperative management.

A 68-year-old man underwent coronary artery bypass grafting (CABG) and developed recurrent arterial thrombosis with an abrupt platelet decline prompting evaluation for HIT. Platelet factor 4/heparin immunoassays were positive, whereas serotonin release assays remained negative during potent P2Y₁₂ receptor inhibition. Despite discordant laboratory results, a probable diagnosis of HIT was made. In addition to fulfilling other diagnostic criteria, genetic testing revealed a JAK2 V617F mutation, confirming the diagnosis of ET.

Unexplained persistent thrombocytosis in the setting of prior arterial thrombosis should raise suspicion for an underlying myeloproliferative neoplasm. Moreover, the coexistence of JAK2 V617F-positive ET and probable HIT following CABG confers a heightened thrombotic risk and underscores the diagnostic challenges associated with functional HIT assays in the context of potent P2Y₁₂ receptor inhibition.

Persistent unexplained thrombocytosis with prior arterial thrombosis should raise suspicion for an occult myeloproliferative neoplasm, whereas postoperative HIT remains a clinical consideration despite negative functional assays, particularly in the context of potent P2Y₁₂ receptor inhibition.