Primal glomerular diseases - glomerulonephritis. Etiology & pathogenesis. Classification. Microscopic & gross pathomorphology.
Glomerulonephritis is a condition of kidneys diseases characterised by injury to the glomeruli or of small blood vessels in the kidney. There are different types of injury to the glomeruli which result in one or both of the nephrotic or nephritic syndromes.
Nephrotic syndrome is characterised by edema in a person with increased protein in urine and decreased protein in blood, along with increased fat in blood (due to increased production of lipoprotein and decreased lipid catabolism). Glomeruli are affected by inflammation (or hyalinization) that allows proteins such as albumin or immunoglobulins to pass through the cell membrane and appear in the urine. As a response the liver compensates with increased protein production. The loss of proteins in urine
accounts for edema, while the increased protein production accounts for lipoproteins in the blood. Causes can be primary or secondary:
- Primary glomerulonephritis (intrinsic to the kidney)
- Minimal change disease (common in children)
- Histology - appears normal under light microscope. Cells of proximal tubule often have protein droplets and lipids. Only obvious change is uniform and diffuse effacement of foot processes of podocytes
- Focal segmental glomerulosclerosis (common in adults, scarring in glomeruli)
- Histology - Affects only some glomeruli (hence focal), those affected show increased mesangial matrix, loss of capillary lumina, hyalinosis and lipid droplets
- Membranous glomerulonephritis (immune deposits on glomerular basement membrane, autoimmune)
- Histology - diffuse thickening of capillary wall with effacement of foot processes and granular deposits
- Membranoproliferative glomerulonephritis (deposition of antibodies in glomeruli membranes along with inflammation)
- Histology - larger glomeruli, proliferation of mesangial and endothelial cells with thick basement membrane.
- Rapidly progressive glomerulonephritis (presents as nephritic, not nephrotic, syndrome)
- Secondary glomerulonephritis (associated with non-kidney factors)
- Diabetic nephropathy
- Systemic lupus erythematosus
- Sarcoidosis
- Syphilis
- Hepatitis B
Nephritic syndrome is characterised by blood in the urine and a decrease in urine along with presence of hypertension. This syndrome sees inflammatory damage to cells lining the glomerulus which destroy the epithelial barrier which usually keeps RBCs in.
It may present with hematuria, proteinuria or as a nephrotic syndrome, nephritic syndrome, acute or chronic renal failure.
Causes of nephritic syndrome include:
- IgA nephropathy, post-streptococcal glomerulonephritis, hemolytic uremic syndrome and Henoch-Schonlein purpura in children
- Histology (post-streptococcal GN) - increased cellularity of glomerular tufts with subepithelial humps against basement membrane and granular deposits of IgG and complement with the capillary walls
- Goodpasture syndrome, systemic lupus, rapidly progressive glomerulonephritis and infective endocarditis in adults.