Angiotensin II type 1 receptor blocker-induced immune thrombocytopenia: a case report

The development of thrombocytopenia after a dose increase in losartan and subsequently after switching the patient to valsartan is reported.

A 61-year-old Caucasian man presented with epistaxis and gingival bleeding of three weeks duration. Laboratory evaluation revealed a hemoglobin level of 144g/L, a leukocyte count of 16.2×109 cells/L (72.51% neutrophils, 20.1% lymphocytes, 6.8% monocytes, 0.4% eosinophils, 0.2% bands), and a platelet count of 15.0×109 cells/L. Flow cytometry of his peripheral blood showed normal CD4:CD8 ratio and no evidence of any lymphoproliferative disorder. A peripheral smear showed decreased platelets with a few areas of clumping. Four weeks before presentation to the emergency room, his losartan dose was increased to 100mg once daily due to continuously elevated blood pressure readings. He had been maintained on losartan 50mg once daily for five years and previous routine laboratory measurements revealed a baseline platelet count of 248.0×109 cells/L.The patient began receiving an oral prednisone taper and his platelet count returned to a stable value of >200×109 cells/L. Because there was no other probable cause, he was thought to have developed immune thrombocytopenia from the increased losartan dose. Losartan was discontinued and one week later he was switched to valsartan 160mg once daily.Forty-seven days after starting valsartan, the patient presented once again to the emergency room with intermittent epistaxis and gingival bleeding while brushing his teeth of two weeks duration. Laboratory measurement revealed a platelet count of 37×109 cells/L. Valsartan was held and another prednisone taper was initiated. The patient's platelet count recovered upon valsartan discontinuation and in four weeks, his platelet count improved to 214×109 cells/L.

A 61-year-old Caucasian man developed immune thrombocytopenia after an increase in losartan dose and developed immune thrombocytopenia again after he was switched to valsartan.