Atypical Abdominal Ulcer Relapse of Granulomatosis With Polyangiitis Following Renal Transplantation With Bilateral Papillary Renal Cell Carcinoma: A Case Report.

Granulomatosis with polyangiitis (GPA) is a necrotizing small- to medium-vessel vasculitis primarily affecting the respiratory tract and kidneys, with cutaneous involvement recognized but less commonly presenting as deep ulcerative lesions. GPA may progress to end-stage renal disease (ESRD), sometimes requiring renal transplantation, while long-term immunosuppression is associated with an increased risk of malignancy, including renal cell carcinoma (RCC). We present a 30-year-old man diagnosed with GPA at age 19 after presenting with hemoptysis and renal failure, with positive cytoplasmic antineutrophil cytoplasmic antibodies (c-ANCA) and cavitary pulmonary nodules. Despite induction and maintenance immunosuppressive therapy, he progressed to ESRD and underwent renal transplantation in 2019. In 2022, surveillance imaging revealed synchronous bilateral papillary RCC in his native kidneys, requiring bilateral nephrectomy. In 2023, he developed a painful periumbilical abdominal ulcer associated with systemic inflammation, and a biopsy confirmed ANCA-associated vasculitis. He was treated with rituximab, glucocorticoids, and avacopan, resulting in complete ulcer resolution within six months. This case highlights the complex longitudinal course of GPA, including atypical cutaneous relapse after renal transplantation and the development of malignancy, and underscores the need for clinical suspicion for atypical relapse and long-term malignancy surveillance in high-risk patients.