# A Case of Piperacillin-Induced Immune Thrombocytopenia: Diagnostic Challenges and Management

## TL;DR

An elderly woman developed severe low platelet count due to piperacillin, a rare antibiotic-induced immune reaction that was correctly diagnosed and treated.

## Contribution

This case highlights piperacillin as a rare but important cause of drug-induced immune thrombocytopenia.

## Key findings

- Piperacillin was identified as the causative agent of immune thrombocytopenia through drug-dependent IgG antibody detection.
- Platelet count normalized after discontinuing piperacillin and administering IV immunoglobulin.
- DITP was differentiated from other thrombocytopenia causes like TTP and HIT using clinical and laboratory findings.

## Abstract

Drug-induced immune thrombocytopenia (DITP) is a rare yet critical disorder that requires prompt recognition and discontinuation of the causative drug to prevent severe complications. In DITP, platelet-reactive antibodies lead to significant platelet destruction. Heparin-induced thrombocytopenia is the most well-studied; yet, antibiotics have also been described.

Herein is a case of a 97-year-old woman with a history of hypertension and hyperlipidemia who was admitted with rhabdomyolysis and sepsis secondary to choledocholithiasis and gallstone pancreatitis. She was started on intravenous fluids and broad-spectrum antibiotics, including piperacillin-tazobactam and vancomycin. Within days, her platelet count dropped from 323,000/μL to 1,000/μL. Schistocytes and hemolysis were absent on a peripheral smear. The patient had normal coagulation studies, and she had a low 4T (thrombocytopenia, timing of platelet count fall, thrombosis or other sequelae, and other causes for thrombocytopenia) score, ruling out thrombotic microangiopathies, such as disseminated intravascular coagulation (DIC), thrombotic thrombocytopenic purpura (TTP), and heparin-induced thrombocytopenia (HIT), respectively. While immune thrombocytopenic purpura (ITP) was seriously considered, the temporal relationship between the drop in platelet count and the administration of broad-spectrum antibiotics led to greater suspicion of DITP. Piperacillin was suspected to be the cause and was promptly discontinued. The suspicion was subsequently confirmed, as supported by the detection of positive drug-dependent IgG antibodies. The patient’s platelet count normalized within a week after stopping piperacillin and receiving IV immunoglobulin (1 g/kg). Hence, DITP needs to be considered among other causes in patients with acute severe thrombocytopenia, as early recognition and prompt cessation of the offending agent are important for preventing life-threatening hemorrhagic sequelae.