Significance of intrarenal vascular lesions in Ig A nephropathy prognosis.

Background: Immunoglobulin A nephropathy (IgAN) is the predominant primary glomerulonephritis globally and remains a subject of active research with a focus on understanding its course and prognosis. Although vascular lesions are associated with IgAN, the current histopathological grading systems do not consider intrarenal vascular lesions when predicting patient prognosis. Therefore, this retrospective study conducted at Kyungpook National University Hospital between October 2016 and December 2021, aimed to elucidate the significance of intrarenal vascular lesions in IgAN by comparing the clinical data of patients with and without such lesions.

Methods: Data of patients with biopsy-confirmed primary IgAN between October 2016 and June 2021 at Kyungpook National University Hospital (Daegu, South Korea) were collected, and their medical records were reviewed. All slides from these 138 cases were independently pathologically reviewed by two nephropathologists (Y. J. K. and M. S. K.) using light microscope. The vascular lesions included in this study were fibrous intimal thickening, arteriolar wall thickening, and arteriolar hyalinosis. All cases were reviewed according to the Oxford Classification of IgA Nephropathy (2016) and Haas classification.

Results: Of the 138 patients, 88 exhibited at least one intrarenal vascular lesion. Patients with arteriolar wall thickening demonstrated a reduced estimated glomerular filtration rate (eGFR), elevated serum creatinine level and urine protein-to-creatinine ratio, an increased proportion of global glomerulosclerosis, and a higher histologic grade of interstitial fibrosis and tubular atrophy at the time of biopsy.

Conclusion: Arteriolar wall thickening in IgAN are associated with reduced eGFR and global glomerulosclerosis. Moreover, reduced eGFR and global glomerulosclerosis are correlated with the progression to end-stage renal disease. Although the direct correlation between vascular lesions and end-stage renal disease is not entirely clear, a marginally significant association (log-rank test, p = 0.06) was observed with arterial wall thickening. This study suggests the potential importance of vascular lesions in the prognosis of IgAN, encouraging further investigation using larger cohort studies to establish a clearer association.