Approach to the diagnosis of thin basement membrane nephropathy in femaleswith the use of antibodies to type IV collagen

Context.-Thin basement membrane nephropathy is recognized by a diffusely th in glomerular basement membrane (GBM) ultrastructurally. In contrast to Alp ort syndrome (AS), there is no GBM thickening, lamellation, or granular inc lusions. Morphologically, there is overlap between thin basement membrane n ephropathy and AS in female patients in whom there might be only thin GEM a nd no pathognomonic findings of AS. Objective.-To determine if the use of antibodies to collagen IV is helpful in making the distinction between thin basement membrane nephropathy and AS in female patients with primarily thin GBMs. Design.-We examined renal biopsies from 9 adult female patients with thin G BMs for the presence of alpha1, alpha3, alpha4, and alpha5 chains of type I V collagen by immunofluorescence. Results.-In 2 patients with segmental GBM staining, no suggestion for AS wa s found on physical examination or in their family history. In the remainin g 7 patients with normal GBM staining, 4 had family members with end-stage renal disease of unknown etiology, raising the suspicion of X-linked or aut osomal-recessive AS. Three patients were presumed to have thin basement mem brane nephropathy. Conclusion.-Segmental GEM staining for alpha3, alpha4, and alpha5 chains of type IV collagen raises the suspicion of AS in the presence of adequate co ntrols and other supporting evidence. Normal GBM staining for alpha3, alpha 4, and alpha5 chains of type IV collagen, however, does not exclude AS.