A case report of metastatic renal cell carcinoma and ANCA associated vasculitis.

Renal Cell Carcinoma (RCC) may uncommonly present concurrently with anti-neutrophil cytoplasmic antibody (ANCA) associated vasculitis (AAV). Most instances are malignancies discovered incidentally during the work up after a diagnosis of AAV; however, the significant overlap between these disorders potentially suggests a more complex pathophysiology. We present the case of a 53-year-old gentleman who was diagnosed with metastatic RCC who later developed rapidly progressive kidney failure and a vasculitic rash after commencement of a tyrosine kinase inhibitor and was ultimately diagnosed with subsequent concurrent AAV. Treatment included suspending immunotherapy, glucocorticoids, and rituximab induction. This case highlights the unique scenario of concurrent RCC and AAV, including the potential pathophysiology of a pro-inflammatory milieu created in the setting of RCC which permits AAV. It also outlines the complexity of treating an autoimmune disorder in the setting of an active cancer requiring immunotherapy and the difficult balance between these two treatment paradigms.