SUN-377 C3 GLOMERULONEPHRITIS MASQUERADING AS POST-INFECTIOUS GLOMERULONEPHRITIS

Abstract

Post-infectious glomerulonephritis (PIGN) is a self-limiting glomerulonephritis (GN). It manifests as a diffuse endocapillary GN and in immunofluorescence staining (IF) co-deposition of IgG and C3 is commonly seen, as well as C3-dominant glomerular depositions. Classically, there are subepithelial humps on electron microscopy (EM). However, there are reports where the initial histological presentation was PIGN, but the patients turned out to have a chronic C3 glomerulopathy (C3G). The aim of this study was to investigate etiological, histological and clinical factors of these patients. Adult patients with biopsy proven C3G originally presenting as PIGN during 2006-2017 were retrieved from the database of the Department of Pathology. A total of 11 patients were identified, of which 5 patients fulfilled the inclusion criteria. Mean age at presentation was 55 years and 80 % were males. Mean follow-up time was 55 months (Table 1). Three patients had C3G based on the persistence of clinical symptoms, and two were suspected to have C3G based on the EM findings. Only the latter two had a prior infection. One was a kidney transplant patient with polyomavirus infection and the other had endocarditis. All patients had dominant C3 in IF. However, none showed staining for IgG. C1q was positive in two patients, one of whom had a prior infection and one of whom did not (Table 2). All without prior infection had humps in EM (Table 3). Clinical variables at presentation and after follow-up are summarized in Table 4. All patients had hematuria and proteinuria, and only one had a normal creatinine level. Two patients presented with acute kidney failure. One patient died of a malignancy soon after the diagnosis. Her plasma C3 was normal, but no further evaluation of the complement system was performed. Three patients had an elevated plasma level of soluble terminal complement complex (SC5b-9), and two patients had low plasma C3 levels at presentation. In addition, a third patient had transient low plasma C3 levels during follow-up. One patient had initially a reduced activity of the alternative pathway, and one had a transiently reduced activity during follow-up. C3 nephritic factor (C3Nef) was measured in three patients and was negative. During follow-up, it turned positive in two patients. At the end of the follow-up, all the patients had chronic kidney disease, although one patient had only mildly elevated creatinine and no urine findings. Two patients are on dialysis. Three have proteinuria and hematuria. Two patients were treated with immunosuppressive medication (steroids, cyclosporine, mycophenolate and rituximab), without clinical benefit. As PIGN is self-limited, the clinical findings typically resolve within weeks or months. Our patients were all originally diagnosed as PIGN. Two were reclassified as C3GN after EM was performed and three later, as the condition turned out to not be self-limited during follow-up. Reassessment of historical PIGN cases has led to reclassification as C3G in 25 % of the cases. In any patient with a C3-dominant PIGN with persistent clinical abnormalities, investigation of the complement system is warranted.View Large Image Figure ViewerDownload Hi-res image Download (PPT)