Thin basement membrane nephropathy associated with other glomerular diseases.

Many reports confirm that thin basement membrane nephropathy (TBMN) commonly occurs together with other glomerular diseases such as minimal change glomerulonephritis, diabetes, membranous nephropathy, immunoglobulin (Ig)A glomerulonephritis, and focal segmental glomerulosclerosis. We postulate 3 explanations for these observations. The association of minimal change glomerulonephritis with TBMN probably is artifactual whereas the association with diabetes and membranous glomerulonephritis probably is coincidental. However, the link between TBMN and IgA disease and focal segmental glomerulosclerosis may be pathogenetic. Clinical evidence indicates that the presence of an associated glomerulopathy significantly worsens the prognosis of TBMN. Thus, patients with TBMN and another glomerular lesion usually have more marked proteinuria, and are more likely to have hypertension and renal insufficiency. The frequency of another glomerulopathy in patients with TBMN means that all patients in whom TBMN is suspected but who have heavy proteinuria or renal insufficiency should undergo a renal biopsy examination. However, there is no evidence that TBMN alters the prognosis of another glomerulopathy, and, in particular, patients with TBMN and IgA disease do not have different clinical features or a worse prognosis than those with IgA disease alone.