Histomorphological classification of focal segmental glomerulosclerosis: A critical evaluation of clinical, histologic and morphometric features

Primary focal segmental glomerulosclerosis (FSGS) has recently been divided into five subtypes by the Columbia classification. However, little is known about the incidence of these subtypes in the Indian population. In addition, there are very few studies evaluating the clinico-pathologic features with morphometric parameters in these subtypes. This study was aimed at evaluating the clinical, histopathological and morphometric parameters in various subtypes of FSGS at our referral center. Sixty-five (65) cases of idiopathic FSGS, diagnosed over two years (2006-2007), were included in the study. Detailed clinical and biochemical investigations were noted. Histological sections were reviewed and cases classified according to the Columbia classification and various glomerular and tubulo-interstitial features were noted. Glomerular morphometry on digitized images was performed using image analysis software. Renal biopsies with minimal change disease were used as controls for morphometric evaluation. In this study, FSGS not otherwise specified (NOS) was the most common subtype (44.6%), followed by perihilar FSGS (24.6%), collapsing (13.8%), tip (12.3%) and cellular FSGS (4.6%). Collapsing subtype showed significantly shorter duration of symptoms and higher degree of proteinuria, mean serum urea and creatinine compared with the other subtypes. On histologic analysis, features like glomerular hyalinosis, capsular adhesion, mesangial proliferation and visceral epithelial cell prominence (VEP) were frequently seen. The cases with VEP had a shorter duration of symptoms and a higher mean serum creatinine and 24-h urine protein excretion compared with those without VEP. The morphometric study revealed a significant higher mean glomerular area in the NOS, perihilar and collapsing variants as compared with the control biopsies. The present study highlights the differences in the prevalence in the FSGS subtypes in our population compared with the western data. Also, the significant differences in the clinical, biochemical and histological parameters reaffirm the utility of the Columbia classification of FSGS in routine reporting of renal biopsies. We found VEP (without causing collapse of the tuft) to be associated with higher serum creatinine at presentation. This feature needs to be evaluated in further studies for its potential significance.