A Rare Case of ANCA-Associated Vasculitis (AAV) with Concurrent Immune Complex (IC) Deposition

Introduction: AAV is a small-vessel autoimmune disease causing necrotizing inflammation, often leading to rapidly progressive glomerulonephritis (RPGN), which is associated with pauci immune crescentic glomerulonephritis. The coexistence of renal limited AAV with IC deposition is a rare occurrence. Here we present a case of renal limited AAV with concurrent IC deposition. Case Description: A 74-year old male with past medical history of prostate cancer (CA), non-small cell lung CA, basal cell CA, rheumatoid arthritis (on abatacept) and hypertension presented to the hospital with complaint of flank pain. He reported consuming 1.6-2g/day of ibuprofen. Home medications included nifedipine and carvedilol. Initial work up showed serum creatinine (SCr) of 5.6, hemoglobin of 10 and blood urea nitrogen of 64. Urinalysis was positive for 100mg/dL protein, 3+ blood. Urine microscopy revealed dysmorphic RBCs. Renal ultrasound did not reveal any hydronephrosis. Additional workup revealed positive ANA 1:80, negative anti dsDNA, normal C3, C4, negative PR3 and elevated myeloperoxidase (MPO) titres >1:1280 with MPO Ab IgG a 116 AU/mL. Urine protein-to-creatinine ratio was 0.3. Due to worsening SCr up to 9, he was started on pulse dose steroids. Renal biopsy was done and showed severe necrotizing and crescentic glomerulonephritis (GN) consistent with MPO ANCA associated GN. Additional findings included a mild background of IgA nephropathy, acute tubular epithelial injury, interstitial edema and scattered RBC casts. Features of membranous nephropathy were not present. No vascular thrombosis, emboli or arteritis were seen. He received induction treatment with rituximab, steroids and avacopan. He was started on therapeutic plasmapheresis and also received hemodialysis in setting of uremia and volume overload. Patient remains dialysis dependent with follow up at our GN clinic. Discussion: In AAV, it is rare to see IC deposition but increasing cases of deposition of IgA with MPO positive AAV have been reported. Increased IC deposition correlates with more crescentic glomeruli indicating a worse prognosis. However, the deposition of both IgG and IgA co-dominant deposits is still rare. In spite of his aggressive RPGN, we elected not to use cyclophosphamide given his recent malignancies.