Young Life Interrupted: Rapidly Progressive ANCA-Associated Vasculitis in an Adolescent Leading to ESKD, Thrombotic Microangiopathy, and Posterior Reversible Encephalopathy Syndrome

Introduction: ANCA-associated vasculitis (AAV) is rare in adolescents but can cause rapidly progressive glomerulonephritis (RPGN), leading to severe kidney injury and neurologic complications such as posterior reversible encephalopathy syndrome (PRES). Case Description: An 18-year-old male with no significant past medical history presented with fatigue, hemoptysis, seizures, and worsening kidney function. He developed AKI requiring initiation of hemodialysis. Workup revealed C-ANCA positivity (titer 1:80) and elevated PR3 antibody (>8.0), while P-ANCA, anti-MPO, and anti-GBM antibodies were negative. Renal biopsy demonstrated pauci-immune crescentic necrotizing glomerulonephritis affecting 70–80% of glomeruli. Treatment included IV methylprednisolone, plasma exchange (7 sessions), and 4 doses of rituximab - 2 of which overlapped PLEX sessions. Despite immunosuppressive therapy, renal recovery failed, and he was declared ESKD in February 2025. In March 2025, the patient was readmitted with altered mental status and seizures due to a hypertensive emergency. Brain MRI showed findings consistent with atypical PRES; MRA ruled out vasculitis. Bronchoscopy with BAL revealed hemosiderin-laden macrophages consistent with prior diffuse alveolar hemorrhage, without evidence of active pulmonary vasculitis. Infectious workup showed bacterial and fungal pneumonia. A repeat renal biopsy in April 2025 revealed advanced glomerulosclerosis, thrombotic microangiopathy (TMA), and new C3 deposition not seen on prior biopsy. This raised concern for an overlapping complement-mediated process. Functional complement testing was normal; genetic testing for atypical hemolytic uremic syndrome (aHUS) is negative. Pt was declared EKD and is on intermittent hemodialysis. Discussion: This case highlights aggressive ANCA vasculitis in youth complicated by irreversible renal damage, TMA, and PRES. Early diagnosis and comprehensive management, including evaluation for complement-mediated processes, are essential for optimizing outcomes and transplant planning.