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The clinical and patohistologic comparison of crescentic IGA nephropathy and anca associated vasculitis

INTRODUCTION AND AIMS: ANCA associated vasculitis (AAV) patients and some with IgA glomerulonephritis (IgA GN) have patohistologicaly crescentic formations in glomeruli. These are predictors of outcome for these patients and despite this similar patohistological feature there is difference in clinical presentation between IgA GN and AAV. Our aim was to investigate the difference in clinical and patohistologic parameters between crescentic IgA GN (cIgA GN) and AAVs. METHODS: Study included 135 patients (53 with cIgA GN and 82 with AAV). We performed renal biopsy on patients using automatic 16 Gauge needle. Light, immunofluorescent and electron microscopy was performed. We analysed patients according to clinical syndromes at presentation (acute nephritis syndrome-ANS, chronic nephritic syndrome-CNS, rapidly progressive glomerulonephritis/nephritic syndrome-RPGN asymptomatic proteinuria and hematuria-APH), laboratory data (serum creatinine levels, eGFR, 24 hour proteinuria, serum haemoglobin, serum albumin, serum C3 and C4 complement levels) and patohistologic parameters (percentage of crescentic glomeruli, fibrinoid necrosis, interstitial fibrosis and tubular atrophy). Mann U Whitney test was used to compare differences in continuous variables and Chi- square and Fisher exact test for categoric variables. RESULTS: AAV patients were significantly older (median of age 63, IQR=54-70) compared to cIgA GN (median of age 46, IQR=34-56) years ; p<0.0001). cIgA GN patients were predominantly male (79.2%) compared to AAV patients who were predominantly female (57.3% ; p<0.0001). Patients with cIgA GN clinically usually presented with asymptomatic proteinuria/hematuria at the time of biopsy (41.5%) and AVV patients with rapidly progressive glomerulonephritis (54.9%) at the time of biopsy. At the time of diagnosis cIgA GN patients presented with significantly lower serum creatinine levels (127 umol/l ; IQR=102- 246) compared to AAV patients (324.5 umol/l ; IQR=223- 324) and higher eGFR (60.9 ; IQR=30-92 ml/min/1.73m2 in cIgA GN, 22.4 ; IQR=8-25 ml/min/1, 73m2 in AAV patients ; p<0.0001). There was no significant difference in daily proteinuria levels as well as serum C3 complement levels. Haemoglobin levels were significantly lower (p<0.0001) in AAV patients (93 ; IQR=85-106 g/l) compared to IgA GN (131 ; IQR=116-145 g/l) and the same was observed for serum albumin levels (33 ; IQR=28-37 g/l in AAV patients and 39 ; IQR=34-42 g/l in cIgA GN patients ; p<0.0001). Patohistologicaly statistical significance (P<0.0001) was found in percentage of crescents in glomeruli in biopsy sample. AAV patients had higher percentage of crescents, (33 ; IQR=15-65%) as compared to cIgA GN patients (8 ; IQR=6-22%). There was no statistical difference in percentage of IFTA and fibrinoid necrosis. CONCLUSIONS: Crescentic formation in glomeruli signifies severity of disease and is usually paralleled by the severity of clinical presentation. That said, cIgA GN seems to somewhat differ when compared to AAV. In our cohort patohistological differences in terms of crescents are not so big but seem to translate into different clinical presentation. Interestingly in our cohort cIgA GN patients presented predominantly with APH syndrome. This could be due to the fact that AAV are more systemic in nature than IgA GN. It would be interesting to study, weather the same mechanism of forming glomerular crescents applies in both diseases.

iga glomerulonephritisanca-associated vasculitis

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