Great white sighting: a case of heparin-induced thrombosis with thrombocytosis

Heparin-induced thrombocytopenia (HIT) is an immune-mediated adverse response to heparin therapy, characterized by decreased platelet count and increased risk of thrombosis. HIT, without the tell-tale sign of thrombocytopenia, has rarely been described.

Can HIT be diagnosed in the presence of thrombocytosis? What clinical clues and diagnostic tools facilitate accurate diagnosis in such cases?

We report a case of HIT with thrombocytosis in a young male who initially presented after traumatic knee dislocation. HIT was diagnosed clinically through the discovery of a white thrombus during a vascular surgery procedure and corroborated by a positive latex immunoturbidimetric immunoassay (HemosIL HIT-Ab _{(platelet-factor 4(PF4)-heparin)}), a rapid immunoassay.

With its high sensitivity, specificity, and rapid results, the latex immunoturbidimetric immunoassay is a valuable diagnostic tool, even among patients with a seemingly low pretest probability. This case underscores the guidance imparted by Dr Andreas Greinacher: "[HIT] must be considered if thrombosis occurs or progresses despite effective heparinization even in the absence of thrombocytopenia." Access to rapid and effective laboratory testing reduces the probability of diagnostic error.