Alport's syndrome and benign familial haematuria: light and electron microscopic studies of the kidney

Abstract

INTRODUCTION Hereditary nephropathy is clinically characterized by the familial occurrence in successive generations of progressive haematuric nephritis and neural hearing loss. Hereditary nephropathy of Alport's syndrome (AS) and benign familial (recurrent) haematuria (BFH) are morphologically characterized by specific and diagnostically important thickening and splitting of lamina densa of the glomerular basement membranes. Those lesions can be recognized only by electron microscopy. Hereditary nephritis is usually present clinically with haematuria, and new mutations without a family history of haematuria. It is therefore important to differentiate hereditary nephritis from BFH and no familial haematuria. Thus, electron microscopy is essential in diagnosis of haematuria. OBJECTIVE The aim of this study was to describe, by light microscopy, constellation of renal alterations by which hereditary nephropathy can be recognized with high probability as well as to compare the diagnostic validity of the findings observed by light and electron microscopy in AS and BFH. METHOD We examined 48 renal biopsies of the patients with hereditary nephoropathies by light and electron microscopy. Tissue samples were fixed in buffered paraformaldehyde and embedded in paraffin for long-term preservation. For the electron microscopy analysis, the following fixation in 4% glutaraldehyde tissue was postfixed in 1% osmium tetroxide.Thereafter, the following dehydration procedure tissue slices were embedded in epon. RESULTS Our results demonstrated that the interstitial foam cells, foetal-like glomeruli, minimal glomerular abnormalities with stain less intense in basement membranes, mild irregular mesangial widening, focal thickening of Bowman's capsule, foci of dilatation tubules, tubular ectasia and atrophy, erythrocyte tubules casts were present in hereditary nephritis. Additionally, light microscopic biopsy findings in patients with BFH were either normal or revealed minor changes (e.g. increased mesangial matrix). All biopsies were reevaluated by electron microscopy and ultrastructural findings confirmed the diagnosis of hereditary nephropathies. CONCLUSION The findings observed by light microscopy represent an important step that leads to a definitive diagnosis of AS and BFH. The definitive diagnosis, however, depends on electron microscopy.