We report a case of heparin-induced thrombocytopenia (HIT) that developed during hemodialysis (HD) in a patient with ANCA-associated glomerulonephritis. A 91-year-old female with no previous disease history was admitted to our hospital because of rapidly progressive glomerulonephritis manifesting acute renal dysfunction (BUN 105 mg/dL ; Cr 8.2 mg/dL). Concomitant alveolar hemorrhage and an elevated serum level of MPO-ANCA were present. Given her clinical features, she was diagnosed as having either ANCA-associated glomerulonephritis or microscopic polyangitis (MPA). Shortly after admission, continuous HD was started with unfractionated heparin used as an anticoagulant. Thirteen days later, severe thrombocytopenia (1.7×10
4/μL) developed without thromboembolic or hemorrhagic complications. Even after heparin was switched to nafamostat mesilate for further HD, the platelet count remained below 5.0×10
4/μL. Subsequently, anti-heparin/platelet factor 4 (PF4) complex antibody (HIT antibody) was detected in her serum and she was diagnosed with HIT, an immune-mediated disorder caused by heparin exposure leading to thrombocytopenia. We used Argatroban, a synthetic direct thrombin inhibitor, as an alternative anticoagulation therapy. Under this treatment, the platelet count gradually recovered and was maintained above 10×10
4/μL after day 38. Meanwhile, systemic steroid therapy for ANCA-associated nephritis decreased the serum MPO-ANCA level to within the normal range. Renal function also improved, with the serum creatinine level stabilizing at around 4.0 mg/dL. HD was consequently discontinued and the patient was discharged on day 58. HIT is a well-recognized complication of HD, with an overall incidence of 3.9% in patients newly treated with HD. However, it is important to distinguish HIT from thrombocytopenia that can occur in ANCA-associated nephritis for a variety of reasons, such as DIC, drug-induced disorder, and thrombotic microangiopathy. The most feared complication of HIT is venous or arterial thrombosis, with an estimated mortality rate of 20%. In order to avoid this life-threatening complication, early recognition of the disease by full blood count on a regular basis while receiving heparin, and initiation of appropriate treatment are essential.
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