# Drug-Induced Acute Liver Injury Due to Tamoxifen Prophylaxis

## TL;DR

A woman developed severe liver injury from tamoxifen, a breast cancer drug, which improved after stopping the medication and starting treatment.

## Contribution

This case highlights a rare but reversible instance of tamoxifen-induced acute liver injury.

## Key findings

- The patient experienced acute liver injury with bilirubin levels rising to 17.9 mg/dL.
- Symptoms resolved after discontinuing tamoxifen and initiating steroid and ursodiol therapy.
- Bilirubin levels dropped from 17.9 to 2.3 mg/dL over four weeks following treatment.

## Abstract

A 41-year-old female was diagnosed with stage II ductal breast cancer in November 2023. The patient subsequently underwent a bilateral mastectomy and was started on tamoxifen 20 mg as post-operative adjuvant therapy in December 2023. Surveillance positron emission tomography (six months post-mastectomy) confirmed no cancer recurrence prior to symptom onset. Following abdominal pain, nausea and vomiting, pruritus, and jaundice, in the context of an elevated bilirubin level and a 1.5 mm gallstone, tamoxifen treatment was discontinued in July 2024.

In August 2024, the patient presented with recurrent nausea and vomiting, increased abdominal pain, worsening pruritus and jaundice, debilitating back pain, and a weight loss of 20.87 kg. The patient was admitted to the hospital for further workup. Her bilirubin levels were found to be 17.9 mg/dl (normal range: 0.1-1.2 mg/dL). Following subsequent labs and scans such as a hepatobiliary iminodiacetic acid scan, liver biopsy, computerized tomography of the lumbar spine, magnetic resonance imaging of the lumbar spine and bilateral hips, anti-smooth muscle antibody test, and more diagnostic testing, it was determined that the patient was suffering from drug-induced liver injury. After the initiation of steroids and ursodiol, her bilirubin measurements decreased. The patient reported resolution of symptoms a month later, as her bilirubin levels had declined from 17.9 to 2.3 mg/dL over four weeks. This unique presentation of tamoxifen-induced acute liver injury is reversible, and patients on tamoxifen need a frequent comprehensive metabolic panel to detect possible liver injury preemptively.