The nongenetic diagnosis of thin basement membrane nephropathy.

Three disorders, thin basement membrane nephropathy (TBMN), immunoglobulin A nephropathy (IgAN), and Alport syndrome (AS), account for the majority of children and adults with persistent glomerular hematuria. Although there is some clinical overlap between these conditions, they can be distinguished on the basis of family history, extrarenal findings, routine immunofluorescence, and glomerular basement membrane ultrastructure or type IV collagen chain composition. This distinction is important because of the very different prognoses of these conditions.