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

BACKGROUND

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

CASE SUMMARY: 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.

DISCUSSION: 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.

TAKE-HOME MESSAGE: 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.