STAPHYLOCOCCUS-ASSOCIATED GLOMERULONEPHRITIS MIMICKING IGA VASCULITIS IN AN ADULT

Abstract

TOPIC: Critical Care TYPE: Medical Student/Resident Case Reports INTRODUCTION: Staphylococcus-associated glomerulonephritis (SAGN) is an immune complex–mediated glomerulonephritis (GN) which commonly presents with elevated creatinine, microscopic hematuria, and variable proteinuria; but on rare occasions may manifest as vasculitis that closely mimics Henoch-Schonlein Purpura (HSP). CASE PRESENTATION: A 62-year-old male with diabetes mellitus (DM) and liver cirrhosis presented with gangrene of the right hallux after a dog bite. Given concern for gas gangrene, he underwent Guillotine amputation. Blood cultures were positive for Methicillin sensitive staphylococcus aureus (MSSA). He was admitted to the ICU for septic shock and started on vasopressors and broad-spectrum antibiotics. His course was complicated by acute kidney injury (AKI) and a new onset diffuse palpable purpuric rash on day 3 of admission, for which a skin biopsy was performed. His serum creatinine was 1.4 mg/dl on admission and progressively worsened to 2.8 mg/dl requiring continuous renal replacement therapy (CRRT) initiation. Urinalysis showed 1+ protein with large blood and 20-40 red blood cells (RBC) per high power field. Urine microscopy revealed isomorphic RBC without red cell cast. Spot Urine protein-creatinine ratio was 0.4 mg/g. Immune work up was negative except for hypocomplementemia with C3 35 mg/dl, C4 8 mg/dl and CH50 19 unit/ml. Ultrasound abdomen showed cirrhosis. 2D-echocardiogram was negative for vegetations. Transesophageal echocardiogram and renal biopsy were not performed as patient was hemodynamically unstable. He remained critically ill and continued to decline despite initiation of CRRT and died due to refractory shock. Skin biopsy returned later, showing leukocytoclastic vasculitis with IgA deposition, confirming IgA vasculitis. DISCUSSION: SAGN is an immune complex mediated disease that occurs concurrently with staphylococcal infection. Pathophysiology is postulated to involve massive T cell and B cell activation by a staphylococcal superantigen. This leads to release of cytokines with overproduction of antibodies and systemic vasculitis with IgA-staphylococcal antigen immune complex formation and deposition. About 20% of the patients with SAGN present with leukocytoclastic vasculitis and can clinically mimic steroid responsive disease processes such as HSP or cryoglobulinemic vasculitis. Renal biopsy is essential to establish diagnosis as steroid and immunosuppression use in SAGN remain controversial and can worsen infection as well as renal disease. Unfortunately, renal biopsy could not be performed in this patient due to refractory shock; however, diagnosis of SAGN is being preferred owing to clinical characteristics like older age, DM, active MSSA infection and AKI with hypocomplementemia. CONCLUSIONS: It is important to make clinicians aware of the variable presentation of infection related GN, such as SAGN, HSP-nephritis, or post-streptococcal GN as treatment might differ. REFERENCE #1: 1. Akio Koyama, Kobayashi M et al. Glomerulonephritis associated with MRSA infection: A possible role of bacterial superantigen. Kidney International. Doi:10.1038/ki.1995.25 REFERENCE #2: 2. Tahrin Mahmood, Puckrin R et al. Staphylococcus-Associated Glomerulonephritis Mimicking Henoch-Schonlein Purpura and Cryoglobulinemic vasculitis in a patient with an epidural abscess: A case report and brief review of the literature. Can J Kidney Health Dis. 2018. Doi:10.1177/2054358118776325. DISCLOSURES: No relevant relationships by kalpana chintha, source=Web Response No relevant relationships by Stanley Dumond, source=Web Response No relevant relationships by Adam Green, source=Web Response No relevant relationships by Ananya Nanduri, source=Web Response No relevant relationships by Matk Sunga, source=Web Response