THIN GEM NEPHROPATHY - PREMATURE GLOMERULAR OBSOLESCENCE IS ASSOCIATED WITH HYPERTENSION AND LATE-ONSET RENAL-FAILURE

Thin glomerular basement membrane (GEM) nephropathy, also called famil ial benign hematuria, is characterized by chronic hematuria and unifor m thinning of the lamina densa of the glomerular basement membrane. It generally holds an excellent renal prognosis. Alport syndrome in earl y stages can also show attenuation of the GEM; conversely, renal insuf ficiency has been reported in familial benign hematuria. To discern ea rly Alport syndrome from thin GBM nephropathy, we carried out a prospe ctive epidemiological study in which 19 normotensive and non-azotemic adult patients with chronic microscopic (18 of 19) and macroscopic (1 of 19) hematuria and biopsy-proven thin GEM nephropathy were followed for a median of 12 years (range 9 to 15 years). Renal biopsies of thin GBM patients at entry showed an increased incidence of focal global g lomerulosclerosis when compared to disease controls as IgA nephropathy (P = 0.047) and normal renal tissue (P = 0.0075). All renal biopsies showed the presence of the Goodpasture antigen when tested immunohisto chemically. Presence of Alport syndrome was excluded clinically as non e of the patients had complaints of hearing loss or abnormalities by a udiography and ophthalmology. At the end of follow-up, the incidence o f hypertension in thin GEM nephropathy (35%) exceeded that of healthy clinical controls (P = 0.048), and one hypertensive patient developed mild renal failure. In the normotensive patients, the glomerular filtr ation rate at follow-up as measured by inulin clearance was reduced in three out of seven: these were over 50 years of age. Although no fami ly members were known to have renal disease at inclusion, within four families six elderly first degree relatives had developed unexplained renal insufficiency at the end of follow-up. Thus, thin GEM nephropath y predisposes to premature glomerular obsolescence. leading in time to increased incidences of hypertension and late onset renal insufficien cy.