Histological features and data on the natural history after 1 to 45 years (mean 6.56 +/- 8.55) of total apparent duration and 1 to 13 years (mean 3.48 +/- 5.04) of post-biopsy follow-up, are reported in 374 patients (mean age, 33.9 +/- 11.9 yrs) with idiopathic mesangial IgA nephropathy, who presented with a history of macroscopic hematuria (56%), recurrent in two-thirds of the patients, or with persistent microscopic hematuria and no previous episodes of gross hematuria (44%). Mesangial cell proliferation ranged from minimal to diffuse. Associated varying degrees of extracapillary proliferation, segmental and global glomerular sclerosis, tubulo-interstitial damage and arteriolar hyalinosis usually correlated with each other and with the extent of mesangial proliferation (P less than 0.05). The actuarial curve of progression to renal death showed a 75% survival after 20 years from apparent onset. Progression to renal failure was more rapid in patients with: an older age at onset (P = 0.0582); male sex (P = 0.0730); no history of recurrent gross hematuria (P = 0.0406); high blood pressure (P = 0.0011); more marked global (P = 0.0007) and segmental (P = 0.0026) glomerular sclerosis; more severe interstitial sclerosis (P = 0.0147); more diffuse and global mesangial proliferation (P = 0.0820); mesangio-parietal pattern at immunofluorescence (P = 0.0778). However, all these parameters showed a poor predictive value if applied to any single patient.
