Tonsillar histomorphometry in IgA nephropathy: a cross-sectional study of correlations between clinical and renal histopathological findings

Abstract There is insufficient evidence to confirm the involvement of tonsillar immune disorders in the pathogenesis of IgA nephropathy (IgAN). This cross-sectional study investigated the association between histological changes in the palatine tonsil, its clinical presentation, and renal histopathological findings in IgAN. Eighty-seven patients with IgAN who underwent tonsillectomy within one year of undergoing renal biopsy were compared with 27 age-matched patients with recurrent tonsillitis (RT). The mean lymphoid follicle and germinal center sizes in patients with IgAN were significantly smaller than in those with RT (P < 0.001). The relative areas of lymphoid follicles (%LFA) and germinal centers in the total tonsillar tissue were smaller in IgAN than in RT (P < 0.001). The mean interfollicular area was larger in patients with IgAN than those with RT. Crypt epithelia in IgAN showed more expanded non-reticular areas lacking lymphoepithelial symbiosis than those observed in RT (P = 0.003). Lower %LFA was associated with higher urinary protein excretion (P = 0.01) and a longer period from the onset of urinary abnormalities to renal biopsy. A lower %LFA was associated with S and C lesions in the Oxford classification. The frequency of glomeruli with sclerotic lesions showed a close inverse correlation with %LFA (ρ = -0.46, P < 0.001). Reduced size of lymphoid follicles and germinal centers, enlarged interfollicular areas, and expanded non-reticular crypt epithelia in the palatine tonsils were prominent IgAN features. Reduced %LFA showed a significant correlation with IgAN renal histopathological severity, supporting the concept of accelerated involution of secondary lymphoid follicles during IgAN progression.