Weatherly's Woes - Glomerulus

GLOMERULAR DISEASES

Broken filter

Congratulations on making it this far! You’ve now officially reached the most difficult topic in all of medicine! These diseases are rare, obscure, numerous, complicated, poorly understood, histology-heavy, detailed and bizarrely named. I did my best to simplify the material, but making glomerular diseases easy is no easy task so bear with me.

The glomerulus is a filter. It turns blood into pee. The filter can break in two different ways.

In Nephrotic diseases, proteins slip through the filter.

In Nephritic diseases, red blood cells slip through.

NEPHRITIC VS. NEPHROTIC

*Low albumin → fluid shifts from blood vessels to ICF → essentially dehydration → RAAS activation → very mild decrease in GFR

IMMUNOFLUORESCENCE

It sure seems like a lot of nephritic and nephrotic diseases involve antibodies, huh? Well we can take advantage of that fact. Immunofluorescence is a staining technique that highlights antibodies! These images have a characteristic black-and-green appearance.

In type 2 hypersensitivity reactions, antibodies seek out the glomerulus like heat-seeking missiles. The antibodies coat every available nanometer of the glomerulus. This produces a smooth, even line on immunofluorescence.

In type 3 hypersensitivity reactions, antibody-antigen complexes are inadvertently filtered through the glomerulus, like trash caught in a fishing net. This produces a clumpy, granular appearance on immunofluorescence.

Vasculitis can also cause RPGN, but its immunofluorescence pattern is normal.

Pathology of Glomerulonephritis