Thin basement membrane nephropathy (TBMN, also called thin basement membrane disease and benign familial hematuria) is a relatively common disorder . The only finding on renal biopsy is diffuse thinning of the glomerular basement membranes requiring electron microscopy for the diagnosis [1-4].
This disorder is often familial, with a family history of hematuria being noted in 30 to 50 percent of cases. TBMN seems to account for most cases of what has been called benign familial hematuria. Several mutations of the type IV collagen genes COL4A3 and COL4A4 have been identified in patients with thin basement membrane nephropathy, but such mutations are not present in all families .
Thin basement membrane nephropathy will be discussed in this topic review. Alport syndrome is presented separately. (See "Genetics, pathogenesis, and pathology of hereditary nephritis (Alport syndrome)".)
Studies on kidneys used for renal transplantation suggest that the frequency of thin basement membranes in the general population may be as high as 5 to 9 percent [6,7]. However, thin basement membrane disease is clinically diagnosed is less than 1 percent of the population .
It had been suspected that the genetic defect in thin basement membrane nephropathy would be similar to that in hereditary nephritis (Alport syndrome), since patients with the latter group of disorders also have thin basement membranes early in the course of the disease . This hypothesis has been confirmed in families in which thin basement membrane nephropathy was due to heterozygous defects in COL4A3 or COL4A4, the genes that encode for the alpha-3 and alpha-4 chains of type IV collagen [8,10-15]. The entire group of disorders encompassing TBMN and Alport syndrome has been called the Type IV Collagen Nephropathies.