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INTRODUCTION Drug-induced immune thrombocytopenia (DITP) is a rare and often difficult-to-diagnose cause of thrombocytopenia, caused by drug-dependent platelet antibodies leading to increased platelet consumption and destruction. DITP evolves within 7 days of initiation of the offending drug and is characterized by thrombocytopenia, with or without bleeding manifestations. Immediate discontinuation of the inciting drug remains the cornerstone of management. Although the most commonly identified drugs are quinine, penicillamine, and valproic acid, isolated cases of ceftriaxone-induced immune thrombocytopenia have been reported. CASE REPORT A 60-year-old female presented with fever, dysuria, and fatigue for 3 days with associated proximal muscle weakness for a few weeks. She was diagnosed with right pyelonephritis with urine cultures growing non-ESBL (extended-spectrum beta-lactamase) Escherichia Coli for which she was started on Ceftriaxone 2g daily. She was also started on low-dose prednisone 20mg daily for fibromyalgia. Her platelet count continued to downtrend and on day 7 of treatment reached a nadir of 18K/μL. Heparin-induced thrombocytopenia (HIT) was excluded. She received one unit of platelets and ceftriaxone was switched to ceftazidime, with which her platelet counts improved. Owing to the temporal relationship between the development and resolution of thrombocytopenia with the commencement and withdrawal of ceftriaxone, drug-induced thrombocytopenia was diagnosed. Naranjo's algorithm revealed a probable adverse drug reaction but confirmatory tests for ceftriaxone-induced platelet antibodies could not be performed. DISCUSSION DITP remains a diagnosis of exclusion and poses a significant therapeutic challenge. Clinicians need to have a high index of suspicion to rule out common causes of unexplained thrombocytopenia before diagnosing DITP. |
