Porto-Sinusoidal Vascular Liver Disease Associated With Trastuzumab Emtansine: A Case Report.

Porto-sinusoidal vascular disorder (PSVD) is a rare vascular liver disease characterised by alterations in the portal and sinusoidal vasculature in the absence of cirrhosis, often associated with immune conditions, haematological disorders, or medication exposure. We describe a 69-year-old woman with a history of human epidermal growth factor receptor 2 (HER2)-positive invasive breast cancer, treated with 15 cycles of trastuzumab emtansine (T-DM1) from January to October 2020. From the third cycle, she developed an increase in aminotransferase levels to three times the upper limit of normal, which normalized after discontinuation of T-DM1 due to cancer progression. Two years later, she presented to the emergency department with hepatic encephalopathy, lower limb oedema, and signs of portal hypertension. Laboratory tests showed thrombocytopenia and a cytocholestatic pattern, and hepatic venous pressure gradient confirmed portal hypertension. Liver biopsy revealed histological features consistent with PSVD without cirrhosis. A diagnosis of drug-induced PSVD was made, likely secondary to T-DM1. The patient was treated with diuretics and lactulose, with marked clinical improvement and no further complications over one year of follow-up. This case underscores the importance of considering PSVD in patients with unexplained liver dysfunction and portal hypertension following cancer therapy.