primary focal segmental glomerulosclerosis: why are pieces of this puzzle still missing?

Focal segmental glomerulosclerosis (FSGS) can be classified as primary or secondary. Moreover, many causes of primary FSGS have been identified in recent years. In this regard, genetic circulating permeability factors and the abnormal podocyte expression of co-stimulatory molecules have been reported. However, the classification of this entity remains difficult to understand, mainly due to the fact that it describes a morphologic pattern of scarring. FSGS is a histological pattern shared by almost all the glomerulonephritides that describes a podocyte lesion and not a disease. Therefore, it should be reclassified according to the new pathophysiological findings and the biomarkers encountered in each triggered pathway.