Focal segmental glomerulosclerosis (FSGS) is a cause of nephrotic syndrome in children and adolescents, as well as a leading cause of kidney failure in adults.It is also known as "focal glomerular sclerosis" or "focal nodular glomerulosclerosis." It accounts for about a sixth of the cases of nephrotic syndrome.(Minimal change disease (MCD) is by far the most common cause of nephrotic syndrome in children: MCD and primary FSGS may have a similar cause. Five mutually exclusive variants of focal segmental glomerulosclerosis may be distinguished by the pathologic findings seen on renal biopsy: Collapsing variant Glomerular tip lesion variant Cellular variant Perihilar variant Not otherwise specified (NOS) variant. The collapsing variant is associated with higher rate of progression to end-stage renal (hyperophy and necrosis of vascular epithelium is seen)lesion variant has a low rate of progression to end-stage renal disease in most patients. Cellular variant shows similar clinical presentation to collapsing and glomerular tip variant but has intermediate outcomes between these two variants. However, because collapsing and glomerular tip variant show overlapping pathologic features with cellular variant, this intermediate difference in clinical outcomes may reflect a sampling bias in cases of cellular focal segmental glomerulosclerosis (i.e. unsampled collapsing variant or glomerular tip variant). The prognostic significance of perihilar and NOS variants has not yet been determined. The NOS variant is the most common subtype. Collapsing variant is the most common type of glomerulopathy caused by HIV infection Ref Harrison20th edition pg 278