Three cases with collagenation of glomerular basement membrane are presented. The ages of the patients are 8, 13, and 27 years. An 8-year-old boy presented with nephrotic syndrome; a 13-year-old girl presented with recurrent urinary tract infections, proteinuria, and edema; and a 27-year-old woman was noted during the evaluation of a cardiac murmur to have proteinuria and renal insufficiency. The changes on electron microscopy were identical to those observed in nail-patella syndrome, a rare hereditary disease with ectodermal and mesodermal involvement, manifested as bony and nail abnormalities. Nephropathy is now a well established part of this syndrome. Our cases did not have the typical bony and nail changes. We feel these three cases represent a partial gene penetrance or manifestation of only a portion of gene complex involved in this syndrome.