There is marked variation in the frequency of focal segmental glomerulosclerosis (FSGS) around the world. Recent studies of renal biopsy specimen archives from several institutions in the United States suggest that the incidence of FSGS has increased over the past 20 years. Indeed, FSGS has become the leading cause of idiopathic nephrotic syndrome in adults and has become increasingly common in children as well. Further, the data indicate that black individuals are at increased risk for developing idiopathic FSGS as well as FSGS in the setting of human immunodeficiency virus (HIV)-1 infection. Data from around the world suggest great variability in the proportion of glomerular disease that is attributed to FSGS, with recent increases seen in some countries and not in others. Epidemiologic data from the United States Renal Data Systems (USRDS) show that the incidence of end-stage renal disease (ESRD) owing to idiopathic FSGS has increased considerably, both as absolute numbers and as a fraction of the total ESRD incident population, with FSGS now accounting for 3.3% of incident ESRD cases. In the United States, the annual rate of incident FSGS ESRD cases is 7 per million for the general population, 20 per million for black individuals, and 5 per million for white individuals. The numbers of acquired immune deficiency syndrome (AIDS) nephropathy incident ESRD cases increased rapidly until reaching a plateau after 1995. The reasons for the recent increase in idiopathic FSGS and FSGS incident ESRD cases are complex, but these trends are likely caused, at least in part, by a real increase in the incidence of FSGS over the past 10 to 20 years.
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