Case Presentation: 50-year-old Hispanic man with uncontrolled diabetes mellitus type 2 who presented initially in DKA was found to have an epidural abscess and transferred to our tertiary center for neurosurgical management with laminectomy and drainage. Blood cultures grew out MSSA with seeding to his right clavicle and extending into the chest wall and right upper lobe (RUL) lung parenchyma requiring abscess drainage, rib segment removal, and RUL wedge resection. Transthoracic echocardiogram did not show endocardial vegetation and blood cultures were negative after starting treatment with nafcillin. On hospital day #16, the patient developed acute kidney injury (AKI) consistent with intrinsic renal etiology. Serial urinalyses revealed gross hematuria, proteinuria in nephrotic range, and positive urine eosinophils. Physical exam was significant for persistent mild tachycardia and hypertension without edema. SPEP yielded polyclonal gammopathy. Complement levels remained within normal limits and the patient had a normal lipid profile. Results from renal biopsy showed acute tubular necrosis and mesangial IgA/C3 glomerulonephritis (GN) without subepithelial humps. The patient was diagnosed with post-infectious IgA GN. Since discharge, nephrology follow-up visits show a persistent AKI and plateau of nephrotic proteinuria.
Discussion: Renal biopsy is often necessary to determine the etiology of AKI and new onset nephrotic syndrome in adults. In contrast to immune complexes involving IgG or IgM that are associated with post-Streptococcal GN, case reports and retrospective studies of patients with Staphylococcal infection, both MRSA and MSSA, have noted deposition of immune complexes involving IgA. In our case, biopsy showed mesangial but not subepithelial “humps” of glomerular immune complex deposits which were often seen in studies of post-Staphylococcal GN, while polyclonal gammopathy and the absence of hypocomplementemia could be consistent with immunologic etiology. Therefore, his history of uncontrolled diabetes mellitus and MSSA bacteremia with seeding were key diagnostic factors.
Conclusions: This case study is intended to increase awareness about a rare form of GN. Pathology findings from renal biopsy are not pathognomonic for distinguishing infectious IgA-mediated GN from classical IgA nephropathy. Biopsy results must therefore be placed in clinical context to confirm diagnosis and ultimately determine the proper therapeutic course between antibiotics or immunosuppression.
To cite this abstract:Feffer J, Loukas E, Luke M. Beyond Biopsy Results: Post-Infectious Iga Glomerulonephritis. Abstract published at Hospital Medicine 2015, March 29-April 1, National Harbor, Md. Abstract 516. Journal of Hospital Medicine. 2015; 10 (suppl 2). https://www.shmabstracts.com/abstract/beyond-biopsy-results-post-infectious-iga-glomerulonephritis/. Accessed April 4, 2020.