CLINICAL-FEATURES AND OUTCOME OF PATIENTS WITH THIN AND ULTRATHIN GLOMERULAR MEMBRANES

There is considerable disagreement regarding the natural history of re nal disease associated with thin glomerular basement membranes (TGBM). We followed 43 patients (19 male), mean age 41.6 years (range 19-73) for a mean of 88 months (48-140). TGBM was recognized in adults when g lomerular basement membrane thickness, measured from multiple sites in electronmicrographs of renal biopsy tissue as the harmonic mean, was < 320 nm. At presentation, 95% had microscopic haematuria, 12% macrosc opic haematuria, 14% loin pain, 28% proteinuria, and 14% hypertension. There was no difference in GBM width between the sexes (male 258 nm v s. female 251 nm) but there was a significant negative correlation bet ween age and GBM width (r = -0.53, p < 0.001), with older patients hav ing the thinnest membranes. Twenty six patients had ultrathin GBM (< 2 70 nm), of whom 54% had 3+ haematuria vs. 12% of the group with BM > 2 70 nm (p < 0.01). In the ultrathin group, 71% had loss of anionic char ge from the GEM, vs. 17% in those with membranes which were thin but > 270 nm (p < 0.05). Proteinuria occurred more frequently in those with GBM > 270 nm, 65% vs. 8% in the ultrathin group (p < 0.01). Thin GBM were associated with a benign prognosis, as after a mean follow-up of 85 months (48-140), there was no significant change in either serum cr eatinine or mean arterial blood pressure. Patients with ultrathin GEM had greater loss of GBM anionic charge, which might result in both an alteration of flow characteristics within the glomerular capillaries a nd also increased fragility of the glomerular basement membrane with l ikelihood of rupture and resultant macroscopic haematuria.