Olmesartan Worsening Known Thrombocytopenia: A Rare Side Effect of Angiotensin Receptor Blockers: Case Report

We report a case of a 70 year old male patient with a history of thrombocytopenia who presented with headache and dizziness. He was also receiving antihypertensive treatment with an angiotensin receptor blocker (ARB) once a day (olmesartan medoxomil) that was been recently prescribed. His blood count revealed severe thrombocytopenia (PLT:16 x 10⁹/L). Brain computed tomography (CT) revealed minor hemorrhage at the posterior cranial fossa. Based on the initial laboratory and imaging results the presumed diagnosis was refractory thrombocytopenia as part of a myelodysplastic syndrome (MDS). The diagnosis was confirmed by bone-marrow exam. The patient received therapy with g-immunoglobulin, methylprednisolone, vinblastine and romiplostime. Before discharge, a new brain CT scan was performed showing no change and thrombocytopenia remained stable (PLT: 20 x 10⁹/L). ARB was switched to calcium channel blocker. After six months the patient was re-evaluated as an outpatient and presented with a platelet count of 110 x 10⁹/L.

The current case report indicates worsening of a known thrombocytopenia, in a patient with a preexisting MDS, as a possible side effect of an ARB. Drug induced thrombocytopenia is a condition with increasing diagnostic and clinical concerns requiring specific treatment.