Feature of microscopic polyangitis is-
**Core Concept**
Microscopic polyangiitis (MPA) is a type of small vessel vasculitis characterized by inflammation of blood vessels, leading to damage and organ dysfunction. It is a systemic disease that affects multiple organs, including the kidneys, lungs, and skin.
**Why the Correct Answer is Right**
MPA is typically associated with the presence of anti-neutrophil cytoplasmic antibodies (ANCA), particularly anti-myeloperoxidase (MPO) antibodies. The immune complex deposition and complement activation lead to the activation of neutrophils and macrophages, resulting in the release of various inflammatory mediators and the subsequent damage to the blood vessels. The renal involvement in MPA is characterized by rapidly progressive glomerulonephritis, which is a hallmark of the disease.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because granulomatosis with polyangiitis (GPA) is a different type of ANCA-associated vasculitis, typically associated with anti-proteinase 3 (PR3) antibodies and a more prominent upper respiratory tract involvement.
**Option B:** This option is incorrect because eosinophilic granulomatosis with polyangiitis (EGPA) is another type of ANCA-associated vasculitis, characterized by the presence of asthma, eosinophilia, and a more prominent upper respiratory tract involvement.
**Option C:** This option is incorrect because Henoch-Schönlein purpura (HSP) is a small vessel vasculitis that affects children and young adults, typically characterized by the deposition of IgA immune complexes in the affected tissues.
**Clinical Pearl / High-Yield Fact**
MPA is a systemic disease that requires prompt recognition and treatment to prevent organ damage and improve patient outcomes. The presence of ANCA and the absence of granulomas on biopsy are key diagnostic features of MPA.
**Correct Answer:** D.