An immune-related adverse event of Behcet's-like syndrome following pembrolizumab treatment

Background In recent years, the emergence of immunotherapy has renewed therapeutic modality. Different from traditional anti-tumor therapy, immune-related adverse events of skin, gastrointestinal tract, liver, lung, endocrine glands commonly occurred. At present, only one case of immune-related adverse event of Behcet's-like syndrome following pembrolizumab treatment was reported in USA, and no one is reported in China.Case presentation Here, we report a rare case of Behcet's-like symptom following pembrolizumab treatment. A 43-year-old female was diagnosed as lymph node and bone metastasis of adenocarcinoma with unknown primary lesion, probably being of pulmonary origin. She was treated with pembrolizumab 200 mg every three weeks in combination with chemotherapy for 6 cycles, followed by pembrolizumab monotherapy maintenance. However, she developed Behcet's-like syndrome with oral ulcer, genital uler, phlebitis, and vision loss after 9 cycles of pembrolizumab treatment. She was treated with prednisone 5 mg orally three times a day. Two weeks later, dose of glucocorticoid gaven to the patient gradually decreased with improved symptoms. After a treatment-free withdrawal period, the patient requested to continue pembrolizumab treatment. Unfortunately, the above symptoms recurred on the second day following pembrolizumab treatment, and glucocorticoid was taken once again. The symptoms improved and the condition was under control.Conclusions In view of the exponential growth of immunocheckpoint inhibitors (ICIs) in a variety of tumors, we should be alert to related adverse events, especially the rare rheumatic manifestations.