[Thin glomerular membrane nephropathy. Clinico-pathological observations].

In two nephrology centres between 1983 and 1993 among 1545 kidney biopsies 34 cases of thin basement membrane nephropathy have been diagnosed. All patients had a varying degree of microscopic dysmorph haematuria, occasional slight proteinuria--except two nephrotic children; and normal blood pressure with one exception. 5 children and 7 adults experienced repeated bouts of macroscopic haematuria mainly after exercise or upper respiratory tract infection, one child after tonsillectomy. All patients had normal renal function and retained it during the follow-up period (mean 61 months, 3 months to 22 years), except a 46 year old patient, who was found to have the joint occurrence of light chain gammopathy and hypertension. Seven patients had positive family history for microscopic haematuria, in four family members of three patients renal biopsy disclosed mesangioproliferative glomerulonephritis with thin GBM segments. As a cut off value for thin basement membrane nephropathy we considered 264 nm. The morphometric analysis of the electron micrographs revealed a mean thickness of 210 nm. No differences in basement membrane thickness were measured regarding gender, age or the presence of macroscopic haematuria. The thin basement membrane is considered to be the pathological basis and predisposing alteration leading to haematuria.