Focal segmental glomerular sclerosis: the cellular lesion.

The pathological features of 59 renal biopsy specimens with focal segmental glomerular sclerosis (FSG) were correlated with the patient's clinical and laboratory findings at the time of biopsy. Two morphologic patterns were identified: thirty-nine biopsy specimens had only focal segmental scars which were frequently associated with hyaline deposits. In 20 scars which were frequently associated with hyaline deposits. In 20 biopsy specimens with FSG, the glomeruli also contained a cellular lesion. It consisted of hypercellularity in the involved portion of the glomerulus, increased cells in the surrounding Bowman's space, and reactive and proliferative changes in the associated glomerular visceral epithelial cells. The cellular lesion was seen overlying glomerular capillaries with minimal histologic abnormalities and adjacent to scars. However, it was usually superimposed upon a segmental scar or a portion of the glomerulus with collapsed capillaries and wrinkled, folded basement membranes. Immunofluorescence and electron microscopy did not demonstrate significant immune reactants or electron-dense deposits in the glomeruli. Nineteen of 39 patients with only segmental scars had proteinuria equal to or greater than 3.0 g/day, and nine had the nephrotic syndrome. Eighteen of 20 patients with the cellular lesion had proteinuria equal to or greater than 3.0 g/day, and 14 had the nephrotic syndrome. The interval between the onset of proteinuria and biopsy was much shorter in patients with the cellular lesion (3.4 +/- 3 vs. 71.9 +/- 87 months, mean +/- SD, P less than 0.01). This difference was also significant when only those with nephrotic range proteinuria were compared (3.4 +/- 3 vs. 45.6 +/- 73 months, mean +/- SD, P less than 0.01). Patients with FSG, with or without the cellular lesion, were similar with respect to male/female ratio, age, serum creatinine, and diastolic blood pressure. From these observations, we believe that glomerular injury, evidenced by segmental proliferative lesions with signs of epithelial cell injury, is a significant factor in the pathogenesis of FSG.(ABSTRACT TRUNCATED AT 250 WORDS)