Heparin‐induced thrombocytopenia in myeloproliferative disorders: A rare or under‐diagnosed complication?

Abstract

Patients with myeloproliferative disorders (MPD) are prone to develop thrombotic complications and thus frequently receive heparin. Surprisingly heparin-induced thrombocytopenia (HIT) has been rarely reported in MPD and is potentially under-diagnosed due to the relatively high platelet count. We report three patients with MPD who developed HIT; all presented with a relative fall of platelet counts (although without an absolute thrombocytopenia), thrombosis or skin necrosis and a positive test for HIT antibodies (particle gel immunoassay). Risk factors for developing HIT in our patients were exposure to unfractionated heparin, a recent surgical procedure and female gender. We review the literature on HIT in MPD and discuss the diagnosis of HIT in the absence of an absolute thrombocytopenia. Am. J. Hematol. 83:420-423, 2008. V

Heparin-Induced Thrombocytopenia in Patients with Philadelphia-Negative Myeloproliferative Disorders and Unusual Splanchnic or Cerebral Vein Thrombosis

“…However, the timing of platelet count nadir and of thrombotic complications was not in favor of this hypothesis. Moreover, although none of these 3 patients had a ‘true’ thrombocytopenia, this situation is consistent with a recent review showing the development of a true thrombocytopenia in only half of 8 patients with Ph-MPD-associated HIT [9]. On the other hand, 4 of 5 patients who developed new PE while on heparin therapy were given UFH, confirming that the risk of HIT-associated thrombosis is probably greater with UFH than with LMWH [7].…”

“…To the best of our knowledge, the incidence of recurrent thrombosis and HITT in patients with Ph-MPD is not known, since HIT has been reported in only 8 patients [9]. …”

“…Heparin-induced thrombocytopenia (HIT) is a dangerous potential complication of this therapy, characterized by a typical fall in platelet count for at least 50% of the baseline between days 5–10 of heparin therapy, with venous and arterial thrombosis (HITT) occurring in 30–50% of cases [7]. If patients have a thrombocytosis, however, as in the case of Ph-MPD or in surgical patients [8], the drop in platelet count cannot achieve a level of ‘true’ thrombocytopenia and diagnosing HIT is far from easy [9]. …”

Venous thromboembolism in patients with essential thrombocythemia and polycythemia vera

“…Although the incidence of HIT probably is higher in patients treated with unfractionated heparin than lowmolecular-weight heparin, 86 the condition should not be ignored in patients treated with low -molecular-weight heparin. 86 Although good data are lacking, the incidence is probably higher in PV and ET patients than in the general population, 87,88 and the condition is harder to diagnose and probably underestimated in PV and ET patients. 71,87,88 The high platelet count in ET and PV patients demonstrate that physicians should be more attentive to platelet count variations rather than the typical thrombocytopenia threshold.…”

“…86 Although good data are lacking, the incidence is probably higher in PV and ET patients than in the general population, 87,88 and the condition is harder to diagnose and probably underestimated in PV and ET patients. 71,87,88 The high platelet count in ET and PV patients demonstrate that physicians should be more attentive to platelet count variations rather than the typical thrombocytopenia threshold. Therefore, treatment with low-molecular-heparin should be carried out carefully in these patients, keeping a potential diagnosis of HIT in mind.…”