[A clinical and morphological study of thin basement membrane disease (TBMD)]

Among patients with minor glomerular abnormality detected by light microscopy, but without significant finding by immunofluorescent study, fifteen cases showing global thinning of the glomerular basement membrane (GBM) when examined by electron microscopy were investigated as thin basement membrane disease (TBMD). Fourteen cases with a normal GBM thickness were selected as the control group. In the TBMD group, the mean width of the GBM, the distance between the cell membranes of the epithelial and endothelial cells, was 225 +/- 20 nm, whereas it was 354 +/- 42 nm in the control group. Some cases in the control group revealed a thinner GBM than other cases, which suggested the existence of an intermediate type between the TBMD and normal groups. The mean thickness of GBM in the intermediate and other control cases were 299 +/- 6 nm and 388 +/- 9 nm, respectively. In addition to global thinning of the GBM, the characteristic lesions of TBMD, a lucent appearance of the mesangial area (6 cases), widening of the subendothelial space (8 cases), splitting of the GBM (2 cases) and rupture of the GBM (one case) were observed in the TBMD cases, although these changes were mild in degree. A lucent appearance of the mesangium and widening of the subendothelial space were noticed more frequently in the TBMD group, compared with the control group. A common urinary abnormality in the TBMD patients was microscopic hematuria, which was occasionally associated with mild to moderate proteinuria. The renal function remained within the normal range in thirteen cases. Five cases of the TBMD group had members with renal abnormality in their family, of whom two showed renal failure and were undergoing hemodialysis.