Ans. is 'b' i.e. Collapsing Focal segmental glomerulosclerosisThe individual component of the name refers to the appearance of the kidney tissue on biopsy.Focal Only some of the glomeruli are involvedSegmental - Only part of an entire glomerulus is involvedGlomerulosclerosis - Refers to scarring of the glomerulusDepending on the cause it is broadly classified as:-PrimaryWhen no underlying cause is found; usually presents as nephrotic syndrome.SecondaryWhen an underlying cause is identified, usually presents with kidney failure and proteinuriaThis is actually a heterogenous group including numerous causes such as:- - Infections such as HIV (HIV associated nephropathy)Toxins and drugs such as heroin's predominateFamilial formsSecondary to nephron loss and hyperfiltration such as with chronic pyelonephritis and reflux, morbid obesity, diabetes mellitusPathological variantsFive mutually exclusive variants of focal segmental glomerulosclerosis may be distinguished by the pathological findings seen on renal biopsy:-Collapsing variantGlomerular tip lesion variantCellular variantPerihilar variantNot otherwise specified variant (NOS)The NOS variant is the most common subtype.Recognition of these variants has prognostic value in individual with primary focal segmental glomerulosclerosis.The collapsing variant is associated with higher rate of progression to end stage renal disease whereas Glomerular tip lesion variant has 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.The prognostic significance of perihilar and NOS variants has not yet been determined.Also knowGenetic basis of focal segmental glomerulosclerosisDefect in the gene ACTN4 which encodes alpha actinism A second gene associated with FSGS is TRPC6.