Iron Deposition in Renal Biopsy Specimens from Patients with Kidney Diseases

This study was performed to investigate the correlation between clinical parameters and grading of iron deposition in renal biopsy specimens from 102 patients with various kidney diseases. Iron deposition in renal tissues was detected by Berlin blue staining. The extent of iron staining was semiquantitatively graded as negative (Fe(-)), grade 0, or positive (Fe(+)), including faint, grade 1; moderate, grade 2; or severe, grade 3, by light microscopy. Thirty-four of 102 patients (33%) showed positive iron staining. Fe(+) patients had various renal diseases, mainly consisting of 12 patients with immunoglobulin A nephropathy and 5 patients with benign nephrosclerosis. Mean arterial pressure (MAP), serum creatinine (sCr) levels, incidence of hematuria, and urinary N-acetylbeta-D-glucosaminidase (u-NAG) levels in Fe(+) patients were significantly greater than those in Fe(-) patients, and u-NAG levels correlated positively with the extent of iron deposition. Study patients were tentatively divided into two groups according to the extent of iron deposition: group A, patients with grades 2 and 3 staining, and group B, patients with grades 0 and 1 staining. In group A, MAP, sCr level, urinary protein excretion, and the incidence of hematuria were significantly greater than in group B. Our results suggest that the amount of iron deposition in renal tissue may contribute to the progression of chronic renal disease and may be an early and sensitive indicator of renal damage in certain renal diseases.