Background: Extensive global glomerulosclerosis (GS) has been reported in African Americans with hypertension and renal insufficiency, far exceeding that in Caucasians. To assess and compare severity and phenotype of injury in biopsied African Americans and Caucasians who morphologically had hypertensive nephrosclerosis, we performed a retrospective biopsy study.
Methods: All renal biopsies with a histological diagnosis of hypertensive nephrosclerosis from the last 11 years were identified from our clinical files. Lesions of global and segmental sclerosis, interstitial fibrosis and vascular sclerosis were semiquantitatively analyzed as percent involved, or on a 0 to 3 scale, respectively. The phenotypes of global glomerulosclerosis also were categorized as either the solidified (that is, the entire tuft is solidified) or the obsolescent type (that is, Bowman's space is occupied by collagenous material and the tuft is retracted).
Results: Sixty-two patients (19 African Americans, 43 Caucasians) were included in the study. At biopsy, African Americans were younger than Caucasians with higher serum creatinine, but no difference in proteinuria or mean arterial pressure (MAP). African Americans had a marked increase in the solidified form of GS (25 +/- 6 in African Americans vs. 8 +/- 2% in Caucasians, P < 0.01). This extensive solidification of glomeruli was associated with segmental sclerosis in African Americans (38 +/- 10%), contrasting low prevalence of solidified GS in Caucasians with segmental sclerosis (10 +/- 3%, P < 0.05) and in African Americans without segmental sclerosis (10 +/- 4%, P < 0.05). African Americans with segmental sclerosis were younger and clinically expressed a more severe renal disease than Caucasians with this lesion. Interstitial fibrosis was greater in African Americans than in Caucasians (54 +/- 6 vs. 33 +/- 3%, P < 0.01) and correlated with proteinuria and serum creatinine levels, especially in African Americans, and also with GS. Vascular sclerosis was worse in African Americans than in Caucasians (0.96 +/- 0.04 vs. 0.77 +/- 0.08 score, P < 0.05) and did not correlate with GS. By modeling, neither MAP nor age was useful in predicting any morphological lesions and proteinuria accounted only minimally for the variability of GS.
Conclusions: Blood pressure levels and proteinuria did not account for morphological lesions, suggesting other factors (such as genetic factors, microvascular disease) may play a role. The phenotype of GS differs in biopsied African Americans versus Caucasians with hypertensive nephrosclerosis, with a marked increase in the solidified form of GS in African Americans. The association of extensive solidified GS with segmental sclerosis lesions in African Americans, but not in Caucasians, suggests different mechanisms may contribute to the development and progression of sclerosis in these two patient groups.