Trastuzumab-induced systemic capillary leak syndrome in a breast cancer patient

Systemic capillary leak syndrome (SCLS) is a rare health condition. It is characterized by recurrent episodes of generalized edema and severe hypotension along with hypoproteinemia. The condition is under recognized because of its nonspecific signs and symptoms, and high mortality rate. SCLS triggered by trastuzumab, a target drug for Her2-positive breast cancer patients, has not been previously reported. A 59-year-old Chinese woman, diagnosed with breast cancer with accompanying liver and bone metastasis, was treated with 3 cycles of docetaxel with capecitabine and a regimen of 12 cycles of capecitabine with trastuzumab. The patient developed systemic capillary leak syndrome during the 16th cycle of chemotherapy. Post-diagnosis treatment regimen is also presented in the current case report. SCLS has been previously observed in breast cancer patients. However, SCLS incidence post-chemotherapeutic treatment with trastuzumab has not been reported elsewhere. Hence, our report highlights the need for rigorous investigation of the side effects of trastuzumab usage and the increasing need of insightful diagnosis to manage any incidence of SCLS. The case provides valuable experience for treating the uncommon adverse effects of trastuzumab in Her2-positive breast cancer patients.