Background: To chart the epidemiology of primary glomerular disease by means of a prospective regional study in the southern part of The Netherlands.
Methods: Experienced renal technicians collected renal biopsies, blood, and 24-hour urine samples at the bed site in each of the participating hospitals. The material was processed and analyzed at the University Hospital Maastricht. Analysis included light microscopy, immunohistochemistry, and electron microscopy of the biopsies as well as serologic and chemical analysis.
Results: Primary IgA nephropathy (IgAN), membranous glomerulopathy, antineutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis and thin basement membrane nephropathy (TBMN) are the most common primary glomerular diseases in this order of sequence. Our data show the clinical and histologic phenotype of TBMN to be diverse: the vast majority of TBMN has chronic microscopic hematuria, frequently associated with hypertension in late middle age; about 15% of TBMN has in addition substantial proteinuria which is associated in the majority of cases with the lesions of focal segmental glomerulosclerosis (FSGS). In 5% of TBMN a nephrotic syndrome is observed, occasionally associated with FSGS tip lesions.
Conclusion: These results support the notion that TBMN is a disease of genetic heterogeneity; it is not a benign renal condition in a substantial number of patients, particularly those in late middle age.