Glomerular basement membrane thinning in adults: clinicopathological correlations of a new diagnostic approach

We have studied glomerular basal laminar thickness in biopsy material, using a simple technique involving 16 selected measurements per case. Twenty-nine biopsied cases of adult glomerular haematuria were examined together with 'diseased' controls represented by a variety of glomerulopathies including minimal-change disease and IgA nephropathy. 'Normal' control populations were provided by 13 patients with acute-onset renal failure of non-glomerular origin and nine patients undergoing nephrectomy. Analysis of groups determined by the presence or absence of haematuria, the degree of proteinuria and presence or absence of a diagnostically characteristic immunofluorescence pattern showed that the nine patients with haematuria and proteinuria of less than 200 mg/24 h represented a distinct subpopulation with a mean membrane thickness of 225 nm compared to the control mean of 343 nm (P less than 0.0001). All members of this subpopulation had mean values below an arbitrary cut-off value of 270 nm. Within other specific disease categories, sporadic cases had mean membrane thicknesses below this critical value, indicative of an overlap of pathologies. On short-term follow-up there is no evidence that the 'pure' thin-membrane population are subject to any deterioration in renal function. It is of further interest that eight of nine thin-membrane 'syndrome' cases were O Rh positive. This finding may provide a starting point for investigation of a specific genetic defect.