Specific Types of primary GN

1. Acute Diffuse Proliferative GN.

Light microscopy we’ll see hypercellularity (primarily of endothelial cells and mesangial cells)

1. PSGN (post-streptococcal GN) ---cross-reacting Abs to strep forming IC in vasculature.

EM: subepithelial deposition of ICs.

IF: granular

2. Non PSGN --- histologic changes are identical, but etiology is different. This could be a complication after Hepatitis B infection, for. ex.

Acute Diffuse Proliferative GN is characterized by nephritic syndrome.

2. Rapidly Progressive (Crescentic)GN:

   1. idiopathic

   2. secondary to other types of GN such as Goodpasture’s (most common)

A crescent is proliferation of visceral epithelial cells, and therefore obliteration of Bowman’s space (since visceral and parietal epithelial cells sit around Bowman’s space). You also have fibrin and mononuclear cells in a crescent.

3. Membranous GN:

This is #1 cause of nephrotic syndrome in adults—this disease corresponds to Hayman’s model of glomerulonephritis, with abs being made towards epithelial cell antigens.

Light microscopy: thickening of BM as a result of IC deposition (note, even though there is thickening, remember that this thickening is due to IC deposition, which activate complement and cause damage. In other words, it is thickened, but non-functional, hence we see lots of proteins in urine)

EM: subepithelial IC deposits.

IF: granular

Prognosis: poor overall

4. Lipoid Nephrosis (Minimal Change Disease)--this is the #1 cause of nephritic syndrome in children.

Light microscopy: don’t really see much deviation from normal (hence “minimal change”)

EM: loss of foot processes of podocytes, no deposits

IF: negative. There is no IC deposition

Treatment: children respond well to steroids, good prognosis.

5. Focal Segmental Glomerular Sclerosis (FSGS)

Light microscopy: sclerosis of some of the glomeruli (focal), only parts of those glomeruli are affected (segmented)

FSGS could be

1. idiopathic

EM: loss of foot processes

IM: focal deposition of immune complexes (idiopathic, not sure how or why we get these deposits here)

2. secondary to other diseases, most notably HIV or heroin abuse

FSGS causes nephrotic syndrome

prognosis: variable clinical course

6. MembranoProliferative GN:

It causes nephrotic syndrome

It is slowly progressive

There is thickening of BM and proliferation of endothelial, mesangial, epithelial cells (hence, “membranoproliferative”)

Type I:

EM: subendothelial deposition of IC

Type II:

EM: intramembrane deposits of complement (no Ig) b/c there is alternative activation of complement, i.e., IgG/IgM is not involved—can lead to low serum complement. “Tram-track” appearance on EM.

7. IgA Nephropathy ---

This is the most common type of GN in the world

Light microscopy: mesangial deposition of IgA.

It usually affects young individuals after a respiratory infection

EM: dense deposits in mesangial and paramesangial areas .

IF: IC deposition in mesangium

Prognosis: good

8. Goodpasture Disease (only kidney is affected), also known as anti-GBM disease and Goodpasture Syndrome (kidney and lung are affected)

Basically, if you have a patient who presents with symptoms of renal failure and hemoptasis, your differential is quite limited:

1. Goodpasture Syndrome

2. Wegners granulomatosis, which is mediated by ANCA (remember, PMNs become more “sticky” as a result, stick to the capillaries, cause damage to vessels)

Category: Nephrology Notes , Pathology Notes