Enoxaparin-induced reactive thrombocytosis: a case report

Enoxaparin is an anticoagulant that falls in the class of medications called low molecular weight heparins (LMWHs), and is used to prevent or treat patients with deep vein thrombosis (DVT) and pulmonary embolism. Enoxaparin is the most widely used LMWH for DVT prophylaxis following knee or hip replacement surgery. Common side effects of enoxaparin include bleeding, petechiae at the injection site, and thrombocytopenia. However, reactive thrombocytosis is a rarely reported adverse reaction. We managed a patient who developed enoxaparin-associated thrombocytosis, which was completely resolved after treatment cessation.

A 78-year-old female was hospitalized for post-hip replacement rehabilitation. Low molecular weight heparin 40 mg/day was administered subcutaneously to prevent deep venous thrombosis (DVT). At admission, her platelet count was normal (228 × 10⁹/L) and her white blood cell count was slightly elevated (12.91 × 10⁹/L). Seven days after admission, the patient developed thrombocytosis, which peaked on the 14th day (836 × 10⁹/L), while her white blood cell count had returned to normal (8.86 × 10⁹/L). Her therapeutic regimen was reviewed, and enoxaparin was identified as a potentially reversible cause of reactive thrombocytosis. Switching from enoxaparin to rivaroxaban lead to a gradual decrease in the patient's platelet count, which eventually returned to normal levels 16 days after enoxaparin was discontinued. No complications secondary to thrombocytosis was observed, and no conclusion was reached on the use of small doses of aspirin for antithrombotic therapy under these circumstances.

Enoxaparin-induced reactive thrombocytosis should be suspected in patients with thrombocytosis following enoxaparin administration as an anticoagulant to prevent certain complications.