INCREASING INCIDENCE OF FOCAL-SEGMENTAL GLOMERULOSCLEROSIS AMONG ADULT NEPHROPATHIES - A 20-YEAR RENAL BIOPSY STUDY

Studies and textbooks from the 1970s and early 1980s list focal-segmen tal glomerulosclerosis (FSGS) as accounting for 10% to 15% of cases of idiopathic nephrotic syndrome in adults, although a recent review by D'Agati (Kidney Int 46:1223-1241, 1994) reported an approximately seve nfold increase in the incidence of FSGS from 1974 to 1993 in an active renal biopsy practice. To investigate possible changes in the inciden ce of FSGS in our renal biopsy practice, we reviewed reports from all nontransplant, adult (greater than or equal to 18 years) renal biopsie s received in our laboratory from 1974 to 1993, which comprised 7,420 cases. All diagnoses of membranous nephropathy (MN), minimal change ne phropathy (MCN), and FSGS made in each year were compiled; cases clear ly or suspicious of being secondary to an underlying systemic disease, glomerulonephritis, or drug reaction were excluded. Relative frequenc ies of MM, MCN, and FSGS among these three diseases and among all biop sies were calculated for each year of the study. Regression analysis s howed a significant (P < 0.001) increase in the odds of a diagnosis of FSGS over the study period: 7.6% per year among all biopsies and 6.8% per year among cases of FAN, MCN, and FSGS only. Among all biopsies, the yearly incidence of FSGS increased from 4.0% +/- 0.6% (mean +/- SD ) during the period between 1974 and 1979 to 12.2% +/- 20% during the period from 1987 to 1993. The odds of a diagnosis of MN (mean yearly i ncidence, 9.5% +/- 1.9%) did not vary significantly over the study per iod while the odds of a diagnosis of MCN (mean yearly incidence, 4.0% +/- 1.2%) declined at a rate of 2.2% per year (P < 0.03). Frequencies of diagnosis of MN, MCN, and FSGS by two pathologists were almost iden tical. Review of available slides from cases of FSGS revealed 21 (none before 1980) with characteristic histologic features of the collapsin g glomerulopathy (CG) variant of FSGS. No more than four cases of CG w ere observed in any year of the study, end CG accounted for 4.7% of to tal FSGS cases for which diagnostic slides were available. Compared wi th 42 patients with non-CG FSGS, the CG cohort showed a greater percen tage of black patients (86% v 38%), significantly higher mean levels o f serum creatinine (3.8 +/- 2.7 mg/dL v 1.9 +/- 1.5 mg/dL) and urinary protein (14.3 +/- 9.6 g/24 hr v 7.7 +/- 5.8 g/24 hr) at the time of r enal biopsy, and a greater likelihood of and more rapid progression to end-stage renal failure. Our findings confirm an increase in the inci dence of FSGS over the 20 years between 1974 and 1993, both overall an d among primary nephropathies leading to the nephrotic syndrome. In ag reement with others, we find that CG appears to represent a particular ly ''malignant'' variant of FSGS, although in our experience this vari ant is observed relatively infrequently. (C) 1995 by the National Kidn ey Foundation, Inc.