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Kidney Week

Abstract: TH-PO572

Bacterial Endocarditis with Strongly Positive Anti-PR3 ANCA

Session Information

Category: Glomerular Diseases

  • 1401 Glomerular Diseases: From Inflammation to Fibrosis

Author

  • Slater, Andrew, University of Florida, Gainesville, Florida, United States
Introduction

ANCA-associated rapidly progressive glomerulonephritis (GN) should be identified and treated promptly. There are however infectious mimickers of ANCA-associated GN that may present only as a lack of complete pauci-immunity on biopsy. When lack of pauci-immunity is present, it should alert the clinician to a careful search for a causative infectious agent and to reconsider immunosuppressive therapy.

Case Description

A 64-year-old man with a mechanical mitral valve presented with dyspnea and acute kidney injury preceded by months of fatigue and weight loss. He was treated as decompensated heart failure. His first blood culture was negative. Subsequently, microscopic urinalysis showed dysmorphic red blood cells. Serological testing resulted with anti-PR-3 antibody at 955 AU/cc, anti-MPO within the reference range. Renal biopsy was consistent with crescentic GN, but lacking was complete pauci-immunity with mesangial staining for IgG (trace), IgM (1+), C3 (2-3+), C1q (2+). It was thought that he had a PR-3 associated RPGN. HCV, HBV, Anti-GBM antibodies and HIV serologies were negative. He began steroids, rituximab and cyclophosphamide. Subsequently, mixed cryoglobulin testing returned positively. The components C3 and C4 were low. Immunosuppression was discontinued and further infectious workup was repeated. Quantiferon GOLD testing was negative. Four of four blood cultures grew Staph. epidermidis. As he's a cat owner, Bartonella and Coxiella serologies were sent. Bartonella henselae IgM and IgG were both strongly positive, while Q-Fever IgM was less so. Echocardiogram demonstrated a mitral valve vegetation and CT of the abdomen showed splenic infarction (initial Echo and CT negative). He was started on treatment for S. epidermidis bacteremia and B. henselae, both of which could have been the causative agent of endocarditis. He eventually developed uremia and started kidney replacement therapy. He remains dialysis dependent.

Discussion

The decision to initiate immunosuppression is not light. Bartonella henselae has been shown to present as a rapidly progressive GN that mimics ANCA-associated GN through concomitantly elevated PR3-ANCA antibodies. Coxiella burnetii is a documented causative agent of mixed cryoglobulinemia. A level of suspicion for infectious disease should be maintained when pauci-immunity is absent despite clinically rapidly progressive GN in the setting of strong ANCA serological positivity.