Spondyloarthritis-Associated IgA Nephropathy

Abstract

Introduction: IgA nephropathy (IgAN) can be associated with spondyloarthritis (SpA). The course of SpA-associated IgAN remains largely unknown due to the absence of large cohorts.

Methods: This retrospective study included patients with biopsy-proven IgAN and definite SpA. Kidney biopsies were centrally examined and scored according to the IgAN Oxford Classification. Thirty-two patients fulfilled the inclusion criteria, with a male:female ratio of 9:1 and median age of 27 and 37 years at SpA and IgAN diagnosis, respectively. HLA-B27 was positive in 90% of cases, and most patients (60%) presented with ankylosing spondylitis. The mean baseline estimated glomerular filtration rate (eGFR) was 84 ± 26 ml/min per 1.73 m², and the urine protein-to-creatinine ratio was 0.19 g/mmol.

Results: Renal biopsy revealed frequent presence of crescents (33%) and interstitial inflammation (18%). Despite almost constant use of renin-angiotensin system inhibitors, combined with steroids in 13 of 32 patients, renal outcome was particularly poor. After a median follow-up of 5.9 years, 4 patients (12.5%) reached end-stage renal disease and 41% of patients experienced a >50% decrease of eGFR. The mean annual eGFR decline rate was -4.3 ± 6.7 ml/min per 1.73 m². The risk of reaching class IV or V chronic kidney disease (CKD) stage during follow-up was associated with the presence of hypertension, level of proteinuria, and baseline S- and T-scores of the Oxford.

Conclusion: SpA-associated IgAN is associated with a poor renal outcome, despite frequent use of steroids. Tumor necrosis factor (TNF)-α blockade did not appear to influence the rate of eGFR decline in this setting.

Keywords: IgA nephropathy; NSAIDs; TNF-α blockers; ankylosing spondylitis; renal failure; spondyloarthritis.

Graphical abstract

Figure 1

Survival without reaching the combined renal endpoint (chronic kidney disease stage 4 or 5 and/or doubling of serum creatinine). Circles represent censored data. The shaded zone represents the 95% confidence interval.

Figure 2

Effect of anti–tumor necrosis factor α (TNFα) treatment on estimated glomerular filtration rate (eGFR) decline rate (a) and proteinuria (b). When possible (n = 8 patients), the eGFR decline rate and urine protein-to-creatinine ratio (PCR) were calculated before and after anti-TNFα treatment. Dashed lines represent individual patients. Solid gray line represents the average value. Vertical bars represent the SE.