Kidney tubule basement membrane alterations in type II membranoproliferative glomerulonephritis

Fourteen kidney biopsy specimens from nine patients with type II membranoproliferative glomerulonephritis (MPGN) were examined by electron microscopy for tubular basement membrane (TBM) alterations. In all biopsies, laminal densities, charateristic for type II MPGN, were present in the glomerular basement membranes. The TBM alterations observed included: 1) the presence of laminal, and/or discrete, and/or aggregated densities; 2)focal thickening; 3) multilamination; and, 4) vesicular structures. Laminal densities occurred in 6 of the 9 cases examined. All biopsies had TBM densities representative of at least one of the three forms. The occurrence of electron densities in or near the TBM in type II MPGN may have diagnostic value. In those biopsies where tissue is insufficient for immunofluorescence microscopy and where glomeruli are not found on electron microscopy, an electron microscopic search for densities associated with TBMs would be warranted. Although TBM-associated densities are not pathognomonic for type II MPGN, the observation of such densities, espically laminal densities, would be useful in complementing light miccrscopic and clinical findings.