Immunotherapy-associated capillary leak syndrome in endometrial cancer: a case report and review of the literature.

Background: Capillary leak syndrome is a rare immune-adverse related event. There are only 3 reported cases of capillary leak syndrome in patients receiving pembrolizumab, all of which are patients with non-gynecologic squamous cell carcinomas. Here, we present a case report of capillary leak syndrome in a patient with recurrent endometrial carcinoma receiving pembrolizumab. Methods: This is a case report and review of relevant literature. Patient consent was obtained prior to initiation of the report and submission to the journal. Objectives: We describe a 65-year-old female with recurrent mismatch repair deficient (dMMR) FIGO grade 2 endometrioid adenocarcinoma on pembrolizumab maintenance therapy, who presented to the hospital with fatigue, lower extremity vasculitis, anasarca, and fevers of unknown origin. She was found to have hypoalbuminemia and hyponatremia. A broad workup was performed, which was overall unrevealing. She was diagnosed with capillary leak syndrome as a diagnosis of exclusion. The patient was treated with corticosteroids and IVIG with resolution of her symptoms. The patient is not currently on any maintenance therapy and there are no plans to resume pembrolizumab. Conclusion: Our case is the first reported case of capillary leak syndrome secondary to pembrolizumab in a patient with a gynecologic malignancy. Capillary leak syndrome is a diagnosis of exclusion and is treated via immunosuppression with agents such as corticosteroids and IVIG. Expanded awareness of this immune-related adverse event is vital to prompt recognition and treatment.