Vasculitis: Overview

00:00 Alright, first off, what is a vasculitis? So, all the vasculitides are just a group of auto-immune multisystem diseases that can affect all ages, from infants up to elderly patients. All of these vasculitides, however, are characterized by leukocytic inflammation of the vascular walls.

00:20 That's the primary defect. What that causes though is a variety of downstream problems which are all caused by either luminal narrowing which is going to cause downstream tissue ischemia, aneurismal dilatations which is one of the most significant features that we see in polyarteritis nodosa, or you may see vessel wall damage which is going to lead to red blood cells seeping into the skin which can cause hemorrhage or petechiae. In terms of the language here, a hemorrhage of a small vessel leads to petechiae which is anything smaller than 3 mm in size on the skin whereas anything larger that leads to a larger lesion greater than 3 mm we call that an ecchymosis.

00:59 Now keep in mind that with ongoing granulocytic inflammation of the vessel wall, you're going to get lesions that are more indurated and full and therefore palpable. Now, once you've earned the term palpable purpura, you've got to make sure you're thinking about vasculitis because that's the one thing that's going to cause that. Alright. Next up, remember that all the specific vasculitis subtypes that we're going to go through are essentially divided based on the pathology you find under biopsy and the distribution of the affected vessels. Where are the lesions occurring whether it's small, medium, or large. The other factors to think about vasculitis is that most of them are primary but a number of them can occur secondary to other disease processes. And lastly, all of them are completely idiopathic. We don't really know what causes them though we know a lot of different things that are associated with particular sub-types of vasculitis. Alright, so here is a huge schematic showing all the different types of vasculitis all on one slide. Initially we break up the vasculitis types into small, medium, and large vessel vasculitis. Looking over at the small vessel vasculitis group first, we can see that it's further broken up into 2 larger groups, immune complex mediated and ANCA-associated. The ANCA-associated group is also called pauci-immune which simply means that there is not any evidence or any significant evidence of immune complex on the pathologic biopsy of these lesions. The immune complex mediated if you perform biopsies and look at the lesions you're going to find lots of immune complexes there and that group includes cryoglobulinemic vasculitis, IgA vasculitis, and anti-glomerular basement membrane vasculitis. The ANCA-associated group again, eosinophilic granulomatosis with polyangiitis, microscopic polyangiitis, and granulomatosis polyangiitis.

02:50 Those 3 lesions on the bottom we're going to talk about more in detail. All of them are associated with ANCA positivity on serum testing. Moving on to our medium vessel group, that's only 2 significant diseases we have to be mindful of there and that's polyarteritis nodosa which is depicted there in our renal arteriography and then Kawasaki's disease. And then moving on to our last category, large vessel vasculitis. That's going to be giant cell arteritis and Takayasu's vasculitis. Alright, so we're back here with our differential diagnoses and we can see that our first 3 choices are all ANCA-associated small vessel vasculitides. Again, EGPA, GPA, and MPA.

03:33 Incidentally, little sidebar, you'll note that after the pathologic name you'll see a name in parentheses and that's of course an eponym giving homage to some prior physician who discovered the disease. Oftentimes, those prior people are of ill repute and we've attempted to discard those names over the past 5 or 10 years. Instead those prior eponymous descriptions of the disease have been replaced with information in the name that is more indicative of the actual underlying disease process and what you would find on pathology. So, with that caveat, let's move forward. So as I said, the first 3 are ANCA-associated small vessel vasculitides and then we've got anti-GBM disease also a small vessel vasculitides but it is immune complex mediated, and then lastly polyarteritis nodosa which is one of the medium vessel vasculitis.