All of the following are small vessel vasculitis, Except:
**Core Concept**
Small vessel vasculitis refers to inflammation of small blood vessels, typically involving vessels less than 10mm in diameter. This can lead to various clinical manifestations depending on the organ involved, such as skin, kidney, or nervous system.
**Why the Correct Answer is Right**
Small vessel vasculitis is characterized by the presence of immune complexes and complement activation. This leads to the activation of neutrophils and macrophages, causing damage to the blood vessel wall. The most common forms of small vessel vasculitis include Henoch-Schönlein purpura (HSP), microscopic polyangiitis (MPA), and granulomatosis with polyangiitis (GPA), previously known as Wegener's granulomatosis.
**Why Each Wrong Option is Incorrect**
* **Option A:** Polyarteritis nodosa (PAN) is a medium vessel vasculitis, not small vessel vasculitis. PAN primarily affects medium-sized arteries, leading to aneurysm formation and organ damage.
* **Option B:** Giant cell arteritis (GCA) is a large vessel vasculitis, typically affecting the temporal artery. It is characterized by the presence of giant cells and granulomatous inflammation.
* **Option C:** Kawasaki disease is a medium vessel vasculitis, primarily affecting children. It is characterized by fever, rash, and coronary artery aneurysm formation.
**Clinical Pearl / High-Yield Fact**
Remember the "Buerger's disease" mnemonic: **B** - Blood vessels affected; **U** - Unilateral involvement; **E** - Erythromelalgia; **R** - Raynaud's phenomenon; **G** - Granulomatous inflammation; **E** - Endovascular changes; **R** - Renal involvement; **S** - Skin manifestations; **D** - Disease progression. This mnemonic helps differentiate medium vessel vasculitis from small vessel vasculitis.
**Correct Answer: A. Polyarteritis nodosa**