We encountered 4 individuals with Marfan syndrome who presented with m
icrohematuria and proteinuria. In 2 of them, a renal biopsy was perfor
med. The predominant glomerular change by light microscopy was a focal
segmental increase in mesangial matrix with early sclerotic lesions.
Ultrastructurally, there was variable subendothelial widening containi
ng haphazardly arranged microfibrils, 10-13 nm in diameter. Changes in
small arteries present in the biopsies were mild in case 1 and more s
triking in case 2 which consisted of elastolysis and fragmentation and
focal disruption of internal elastic lamina, and focal degenerative c
hanges in the media. In light of observations on the abnormalities of
microfibrillar protein (fibrillin) in the microfibrillar-fiber system
and the presence of abnormal type IV collagen in the connective tissue
s in Marfan syndrome, the glomerular basement membrane alterations may
be related to these defects and lead to microhematuria and proteinuri
a.