C-ANCA associated with
**Core Concept**
C-ANCA (Cytoplasmic Anti-Neutrophil Cytoplasmic Antibodies) is a type of autoantibody associated with vasculitis, particularly Granulomatosis with Polyangiitis (GPA). GPA is a systemic disease characterized by inflammation of the blood vessels, leading to damage of various organs such as the kidneys, lungs, and respiratory tract.
**Why the Correct Answer is Right**
C-ANCA is specifically directed against proteinase 3 (PR3), a serine protease enzyme found in the azurophilic granules of neutrophils. The presence of C-ANCA is highly suggestive of GPA, and its detection is often used as a diagnostic marker. In this condition, the immune system mistakenly attacks the blood vessels, leading to inflammation and damage. The C-ANCA antibodies play a key role in this autoimmune response.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as A-ANCA (also known as p-ANCA) is associated with Microscopic Polyangiitis (MPA), a different type of vasculitis.
**Option B:** This option is incorrect as there is no established association between C-ANCA and this condition.
**Option C:** This option is incorrect as Eosinophilic Granulomatosis with Polyangiitis (EGPA) is associated with P-ANCA, not C-ANCA.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the presence of C-ANCA in a patient with vasculitis is highly suggestive of GPA, and its detection should prompt a thorough investigation of the lungs, kidneys, and respiratory tract for signs of involvement.
**Correct Answer:** C.