All are examples of medium vessel vasculitis EXCEPT?
**Core Concept**
Medium vessel vasculitis refers to inflammation of medium-sized blood vessels, typically between 100-400 micrometers in diameter. This category of vasculitis involves vessels larger than those found in small vessel vasculitis (e.g., vasculitis of arterioles and capillaries) but smaller than those in large vessel vasculitis (e.g., vasculitis of arteries > 400 micrometers in diameter).
**Why the Correct Answer is Right**
Medium vessel vasculitis encompasses conditions such as Kawasaki disease, Polyarteritis Nodosa (PAN), and Takayasu arteritis. These conditions often present with systemic symptoms, including fever, weight loss, and fatigue, in addition to specific organ involvement (e.g., skin, kidneys, or nervous system). The pathophysiology of medium vessel vasculitis typically involves immune complex deposition, anti-neutrophil cytoplasmic antibodies (ANCA), or granulomatous inflammation.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option should list a condition that is actually a small vessel vasculitis, such as Granulomatosis with Polyangiitis (GPA) or Microscopic Polyangiitis (MPA). These conditions involve inflammation of arterioles, capillaries, and venules, rather than medium-sized vessels.
* **Option B:** This option should list a condition that is actually a large vessel vasculitis, such as Giant Cell Arteritis (GCA) or Large Vessel Vasculitis (LVV). These conditions involve inflammation of arteries > 400 micrometers in diameter, rather than medium-sized vessels.
* **Option C:** This option should list a condition that is actually not a vasculitis at all, such as a primary or secondary condition that affects other parts of the body.
**Clinical Pearl / High-Yield Fact**
In medium vessel vasculitis, the presence of systemic symptoms (e.g., fever, weight loss) alongside organ-specific involvement is a key clinical clue. Familiarity with the typical presentations and complications of medium vessel vasculitis is essential for accurate diagnosis and management.
**Correct Answer:** A. Granulomatosis with Polyangiitis (GPA)