Electron microscopy of a biopsy specimen in a patient with IgA nephropathy. Electron dense deposits can be identified in the mesangium (black arrows), which on immunofluorescence would have predominant or co-dominant IgA staining. Note that although mesangial IgA deposits are classic in IgA nephropathy and IgA vasculitis (former Henoch-Schonlein purpura nephritis), they can be seen in other conditions including infection-associated glomerulonephritis, inflammatory bowel disease, malignancies, sarcoidosis, and certain dermatologic conditions. GBM; glomerular basement membrane. RBC; red blood cells. Mes; mesangium. CS; capillary space. Images courtesy of Patrick Walker, MD.
Perihilar variant of focal segmental glomerulosclerosis (FSGS). Hyaline deposition and sclerosis occur at the vascular pole of the glomerulus. This variant is believed to be a secondary form of FSGS, occurring as an adaptive response to other injuries resulting in loss of functioning nephrons, such as in obesity-related kidney disease. Images courtesy of Patrick Walker, MD.
A normal glomerulus (left) and hypertrophied glomerulus (glomerulomegaly, right). Glomerulomegaly is an adaptive response to decreased nephron number (e.g. prematurity) and/or increased demand (e.g. obesity). Patients with glomerulomegaly may have sub-nephrotic or nephrotic-range proteinuria, but other features of nephrotic syndrome are rare. Images courtesy of Patrick Walker, MD.
A normal appearing glomerulus (left) compared to a glomerulus with endocapillary hypercellularity (right). Note the hypercellular capillary loop (red arrow) compared to the normal capillary lumens (black arrows). This histologic feature can be seen in several glomerular disorders, including IgA nephropathy, post-infectious glomerulonephritis, lupus nephritis, and C3 glomerulopathy. Images courtesy of Patrick Walker, MD.
Immunofluorescent staining pattern in a patient with C3 glomerulopathy. There is strong C3 staining in the capillary loops and mesangium. Immunoglobulin staining, such as IgG, is typically absent or at a lower intensity by at least two orders of magnitude than C3. Images courtesy of Patrick Walker, MD.
Membranoproliferative pattern of glomerular injury in a patient with C3 glomerulopathy. This pattern of injury typically has endocapillary proliferation, diffuse capillary wall thickening, increased mesangial matrix, and mesangial proliferation visible on light microscopy, producing a lobular appearance of the glomerular tuft. Images courtesy of Patrick Walker, MD.