IgA Vasculitis as a Potential Complication of Fourth-Line Chemotherapy with Tegafur/Gimeracil/Oteracil (S-1) in Advanced Non-Small Cell Lung Cancer: A Case Report

BACKGROUND Immunoglobulin A (IgA) vasculitis is a systemic vasculitis that involves the small vessels. It is mainly characterized by skin symptoms such as purpura, arthritis/arthralgia, abdominal symptoms, and nephropathy, which are caused by IgA adherence to the vessel walls. Herein, we report the case of an advanced non-small cell lung cancer (NSCLC) and a purpuric skin rash of the legs that developed during fourth-line chemotherapy with tegafur/gimeracil/oteracil (S-1). CASE REPORT A 68-year-old man diagnosed with NSCLC 2 years ago was undergoing S-1 as fourth-line chemotherapy when he developed purpura and edema on the lower extremities. Biopsy renal specimens were consistent with IgA vasculitis. Considering his medical history, both IgA vasculitis induced by S-1 and a paraneoplastic syndrome were considered, although the exact cause could not be identified. Subsequently, chemotherapy was discontinued because of his deteriorating general condition, and he received optimal supportive care. The purpura spontaneously disappeared; however, his ascites and renal function deteriorated. Systemic steroids improved renal function, but the ascites did not resolve. One month after being diagnosed with IgA vasculitis, the patient died due to deterioration of his general condition. CONCLUSIONS This case emphasizes the occurrence of IgA vasculitis during lung cancer treatment and its potential impact on the disease course of lung cancer. Moreover, the possible causes of IgA vasculitis in this case were paraneoplastic syndrome or S-1 adverse effects, but further case series are needed to gain a more comprehensive understanding. Refractory, steroid-unresponsive ascites may occur as an abdominal manifestation of IgA vasculitis.