Increasing incidence of focal segmental glomerulosclerosis and an examination of demographic patterns

Abstract

Idiopathic focal segmental glomerulosclerosis (FSGS) is one of the leading causes of the nephrotic syndrome in adults and an important cause of end-stage renal disease. Its incidence has dramatically increased in the last two decades and it is especially prevalent among black patients. The trend of FSGS incidence has not been reported beyond 1997. We retrospectively reviewed all renal biopsies performed at our institution between 1986 and 2002 and identified patients with diagnoses consistent with primary glomerulopathy (PG), which included: minimal-change disease (MCD), idiopathic focal segmental glomerulosclerosis (FSGS), membranous nephropathy (MGN), IgA nephropathy (IgA), membrano-proliferative glomerulonephritis (MPGN) and mesangioproliferative glomerulonephritis. Patients with possible secondary causes for their renal disease were excluded. Clinical data at the time of biopsy and follow-up data were collected and analyzed. During the period from January 1986-December 2002, 299 renal biopsies were performed and 132 patients were diagnosed with PG. FSGS was the most common form of PG representing 37.8% of all PG followed by IgA 27.3%, MGN 16.6% and MCD 9.1%. Among FSGS patients 59% were females, 64% had nephrotic range proteinuria and 54% had the nephrotic syndrome. Mean serum creatinine was 2.0 +/- 0.2 mg/dl and mean protein excretion was 6.1 +/- 1.0 g/day. The incidence of FSGS increased from 19.3% (1986-1991) and 16.6% (1992-1997) to 58.5% in the period from 2002. The increase occurred among black and Hispanic patients (33.3-79.2%) as well as white patients (12.5-51.5%). Black and Hispanic patients with PG presented for renal biopsy at a significantly younger age than white patients (p = 0.003), with mean age 37.5 +/- 2.0 years vs. 50.3 +/- 1.8 years. White FSGS patients were significantly older than white non-FSGS patients (mean age 56.4 +/- 3.2 years vs. 48.0 +/- 2.0 years, p = 0.03). Black and Hispanic FSGS patients were also older when compared to their non-FSGS counter-parts (mean age 40.6 +/- 2.8 years vs. 32.1 +/- 2.0 years, p = 0.04). When patients were stratified by age (< 45 years and > or = 45 years), FSGS was the most common diagnosis in both age groups among black and Hispanic patients (55.1% and 88.8%) but only among older white patients (36.2%). The incidence of FSGS as a proportion of PG in our population has increased markedly in the most recent time period analyzed (1998-2002). The increase has occurred among both white and black and Hispanic patients. We also found that FSGS was most prevalent in patients > or = 45 years.