Abstract
Background and Objectives: Glomerular C4d deposits are associated the severity and outcomes of IgA nephropathy. Whether this holds true in immunoglobulin A vasculitis (IgAV) is not known. The main objective of the study was to analyze the prognostic value of glomerular C4d immunolabelling on kidney impairment in adults with IgAV.Design, Setting, Participants, Measurements: This retrospective cohort study included 120 adults with IgAV and a kidney biopsy performed between 1995 and 2018 in two French university hospital centers. All paraffin-embedded biopsies were reassessed according to Oxford classification. Immunofluorescence for C4d was performed in all cases. For analysis, patients were grouped according to positivity for C4d in the glomerular area. The main outcome was a composite endpoint of 50% increase in 24 h-proteinuria, or eGFR decrease by 50%, or kidney replacement therapy.Results: The median follow-up was 28.3 months. Twenty-three patients met the composite endpoint, 12 for kidney replacement therapy, 6 for an eGFR decrease >50% and 5 for a >50% increase in proteinuria. At time of biopsy, the median proteinuria was 1.9 g/24 h and the median eGFR 73.5 mL/min/1.73 m2. Among the 102 patients evaluable for C4d, 24 were positive on >30% glomeruli, mainly with a parieto-mesangial pattern. In this group, the initial proteinuria was more frequently nephrotic than in the C4d– group (60% vs. 33%, P = 0.039). Mesangial hypercellularity was more frequent in the C4d+ group (42% vs. 13%; P = 0.006) whereas macroscopic hematuria was more frequent in the C4d– group (18% vs. 0%; P = 0.03). After a median follow-up of 28 months, kidney survival did not differ according to C4d status.Conclusion: In a population of adult IgAV patients, glomerular positivity for C4d was associated with the severity of the kidney disease at presentation, but not with subsequent renal function deterioration.
Highlights
Immunoglobulin A vasculitis (IgAV), formerly called HenochSchönlein purpura, is an immune complex vasculitis predominantly affecting small vessels with dominant IgA deposits
IgA vasculitis is considered to be a systemic form of IgA nephropathy and it has been suggested that the two conditions are different manifestations of a single disease process [1]
As outlined by AudemardVerger et al [2], a kidney involvement occurs in 45–85% of cases, but IgA vasculitis is responsible for only 0.6–2% of adult nephropathies
Summary
Immunoglobulin A vasculitis (IgAV), formerly called HenochSchönlein purpura, is an immune complex vasculitis predominantly affecting small vessels with dominant IgA deposits. It can affect the skin, gut, joints and kidney to varying degrees. In addition to IgA deposits, glomerular deposition of complement factors including C3, mannan-binding lectin, L-ficolin, mannan-associated serine protease, and C4d has been observed in most patients with IgA vasculitis. These findings, together with the absence of C1q deposits, support the hypothesis of prevalent activation of the lectin pathway. The main objective of the study was to analyze the prognostic value of glomerular C4d immunolabelling on kidney impairment in adults with IgAV
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