Author(s): Koo TY, Park MH
Background IgA-dominant acute postinfectious glomerulonephritis (APIGN) is a recently recognized morphologic variant of APIGN, but its clinicopathologic features were not clearly characterized. We will present demographic, clinical and renal biopsy findings from seven patients with IgA-dominant APIGN with a literature review. Methods All renal biopsy specimens (n=1,119) processed by the Department of Pathology in Hanyang University Hospital from 2005 to 2009 were reviewed. Seven patients with IgA-dominant APIGN were identified, and their clinical data analyzed. Results All patients had renal failure, hematuria and proteinuria. One was diabetic, and none of the patients had previous renal diseases. Three had clinical infections at the time of presentation: 2 with methicillin-resistant Staphylococcus aureus and one with rickettsial infection. Light microscopically diffuse endocapillary proliferative and exudative glomerulonephritis was found in all cases. Immunofluorescence microscopy showed granular IgA deposits along peripheral capillary walls and in mesangium. Ultrastructurally, subepithelial 'humps' with mesangial deposits were noted. End-stage renal disease developed in two patients, chronic renal failure was stationary in two, and azotemia improved in three. Conclusions Various infections including rickettsiosis preceded IgA-dominant APIGN in both diabetics and nondiabetics. Because the prognosis of IgA-dominant APIGN is poor, early diagnosis based on renal biopsy is required. Key words: Postinfectious glomerulonephritis; Immunoglobulin A; Renal biopsy Go to : Goto Acute postinfectious glomeruonephritis (APIGN) is an immune complex-mediated form of glomerulonephritis that follows non-renal infection, often caused by Streptococci. It mostly affects children after an upper respiratory tract infection or impetigo. The typical histological pattern of APIGN includes: diffuse endocapillary proliferative and exudative glomerulonephritis (GN) on light microscopy (LM), coarsely granular deposition of IgG and C3 in a predominantly capillary wall distribution on immunofluorescence (IF), and characteristic subepithelial hump-shaped deposits on electron microscopy (EM). Over recent decades, the spectrum of the disease has been changed. Not only Streptococci but also other bacterial, viral, and parasitic organisms have been implicated in the pathogenesis of postinfectious glomerulonephritis (PIGN).1-3 Extensive use of renal biopsy has demonstrated the presence of atypical histological features of PIGN. Recently, there have been several reports of PIGN with IgA-dominant immune complex deposition, mostly related to staphylococcal infection, especially in patients with underlying diabetic nephropathy.4-19 IgA-dominant PIGN is characterized by diffuse endocapillary proliferative GN on LM, intense deposits of IgA as the dominant or co-dominant immunoglobulin on IF, along with mesangial and subepithelial electron dense deposits on EM.9 However, there have been additional reports of IgA-dominant PIGN that lacked typical features such as diffuse endocapillary hypercellularity, subepithelial deposits, underlying diabetes mellitus and history of infection.11,12,15,17-19 Therefore, to avoid potential ambiguity, the clinicopathological features of IgA-dominant PIGN need to be investigated. Here we present seven cases of APIGN which showed IgA-dominant deposition on renal biopsy. Clinical features and renal pathologic findings were analyzed and discussed with a review of the literature.