Rationale & Objective

Renal arteriolar microangiopathic lesions may occur in immunoglobulin A nephropathy (IgAN), but their role in disease progression remains unclear. We sought to understand the prevalence and character of microangiopathic lesions in IgAN and their role in disease progression.

Study Design

A retrospective cohort study.

Setting & Participants

In this study, we enrolled a Chinese cohort with 944 adult patients with IgAN who had been followed up for at least 1 year.

Predictors

Renal arteriolar microangiopathic lesions.

Outcomes

Composite kidney end point event defined as a >50% reduction in estimated glomerular filtration rate, end-stage kidney disease, or death.

Analytical Approach

All kidney biopsies were independently reviewed by 2 investigators. Renal arteriolar microangiopathic lesions were detected using light microscopy. Multivariable Cox regression analysis was used to test the association between microangiopathic lesions and the outcomes.

Results

Overall, 194 (20.6%) patients had renal arteriolar microangiopathic lesions. Patients with microangiopathic lesions presented with higher blood pressures, more severe proteinuria, and lower estimated glomerular filtration rates (all P < 0.001) than patients without microangiopathic lesions. After a median follow-up of 4.2 years, 75 (38.7%) patients with microangiopathic lesions and 83 (11.1%) patients without these lesions reached the composite kidney end point (P < 0.001). In a multivariable Cox regression model adjusting for clinical and pathologic variables available at the time of biopsy, the presence of microangiopathic lesions was an independent risk factor for kidney failure (HR, 1.95; 95% CI, 1.34-2.83; P < 0.001). Renal vascular sclerosis (arterial intimal fibrosis or arteriolar hyalinosis) was not a risk factor for kidney disease progression (P = 0.5).

Limitations

A single Chinese center’s experience, retrospective study, most patients were not tested for hemolytic markers (for example, haptoglobin level, lactate dehydrogenase level, and schistocytes).

Conclusions

Renal arteriolar microangiopathic lesions are frequent in IgAN and their presence is independently associated with progression to kidney failure. If confirmed in other patient cohorts, such lesions could be considered for inclusion in formal classification schemes of IgAN.