Vasculitis

With vasculitis, you have “inflammation”, of the “blood vessels”, and even though this can happen in arteries or veins, we’re going to focus on vasculitis in arteries because it’s way more common.

Vasculitides—plural for vasculitis—are categorized by the size of the blood vessels they affect, so we have small-vessel, medium-vessel, and large-vessel vasculitis.

Typically vasculitis is due to an autoimmune disease, where the immune system confuses a part of normal body as a foreign invader, and there are a couple of ways this might happen.

Sometimes the body confuses the innermost layer of the blood vessel, which is the endothelial layer, with a foreign pathogen and directly attacks it.

To be a little bit more specific, the white blood cells of the immune system mix up the normal antigens on the endothelial cells with the antigens of foreign invaders like bacteria simply because they look similar—and this is called molecular mimicry.

This autoimmune confusion is thought to be the cause several types of medium-vessel and large-vessel vasculitides.

Other times the immune system attacks healthy cells that are near the vascular endothelium, and the endothelial cells are only getting indirectly damaged.

This is the situation in many small-vessel vasculitides, where the immune system attacks white blood cell enzymes or other non-endothelial cell targets.

Once the endothelium is damaged either directly or indirectly, almost all vasculitis diseases progress in a similar way.

The damaged endothelium exposes the underlying collagen and tissue factor, and these exposed materials increase the chance of blood coagulation.

The blood vessel walls themselves get weaker as they’re more damaged, making aneurysms more likely.

And finally as the vessel wall heals, it becomes harder and stiffer because fibrin is deposited into the vessel walls as part of the healing process.

And actually, that’s vasculitis in a nutshell.

The different types of vasculitis for the most part only vary depending on how they are triggered and where in the body they cause problems.

People with vasculitis have generalized symptoms caused by the inflammatory response of the immune system.

Symptoms like fever, weight loss, fatigue, and so on.

More specific symptoms occur usually based off where in body the vasculitis is occurring, and which organ is supplied by that blood vessel.