How to diagnose kidney focal segmental glomerulosclerosis histology?
Answers
The characteristic histologic feature is sclerosis of segments of the glomerular tuft in some glomeruli (“segmental and focal”), with mesangial expansion and capillary lumen loss in these segments. The injury can be more notorious in the vascular pole or in the periphery of the tuft. When advancing the process the sclerosis becomes global and is indistinguishable of the secondary sclerosis to other diseases. The sclerosing segments are positive with PAS and silver-methenamine stains (type IV collagen). From the Fifties it is said that juxtamedullary glomeruli are more compromised by the segmental lesions. There are, in many cases, podocyte hypertrophy and hyperplasia, mainly on the surface of the sclerosed tuft segment (“cap lesion” or “cellular lesion”). Podocytes frequently appear with protein droplets and lipid resorption. The glomeruli without sclerosing lesions can appear normal or with increase of the mesangial cellularity and, sometimes, hypertrophic (glomerulomegaly).
Focal and segmental glomerulosclerosis (FSGS) is a disease characterized morphologically by segments of sclerosis in some glomeruli. It can be primary or secondary and it usually present as nephrotic syndrome (NS). The glomeruli without segmental lesions can display alterations of the mesangial cellularity and/or loss (“effacement”) of podocyte foot process.
The term “sclerosis” means healing and it is characterized by accumulation of glomerular collagen (type IV). Nevertheless, in FSGS some of the segmental lesions are not sclerosis, but hyaline deposits: Hyalinosis. This feature originated the classical denomination, more of the French school, focal and segmental hyalinosis. Other investigators designate those cases in which there are hyaline segments: “FSGS with hyalinosis”. There is no a clear explanation why in some cases there are hyaline segments and in other no. Some authors consider that hyaline lesions are precursory of those sclerosing; nevertheless, seems that in many cases sclerosing lesions begins thus, without a phase of hyalinosis.