Thin basement membrane syndrome in adults.

Eight (two men, six women) cases of adult thin basement membrane syndrome were studied to clarify the clinicopathological characteristics of the disease. The average age at the time of biopsy was 40 years. All the patients had persistent microscopic haematuria, normal renal function, and normal blood pressure, with the exception of one who was hypotensive. Most of them had persistent or transient proteinuria. Renal symptoms were found in four families, although no relative had Alport's syndrome. Renal biopsy findings observed by light and immunofluorescence microscopy did not indicate any important abnormalities, but extensive diffuse thinning of the glomerular basement membrane, ranging from 153 to 213 nm, was a constant finding by electron microscopy. All the patients retained stable renal function at the time of final follow up, indicating a benign prognosis of the syndrome.