A female who presented with cough with bloody sputum is diagnosed of having granulomatosis with polyangitis. Which of the following is the characteristic histological feature of granulomatosis with polyangitis:
First, I need to recall what GPA is. GPA is a type of vasculitis, specifically an ANCA-associated vasculitis. The key features are granulomatous inflammation and necrotizing vasculitis. Histologically, GPA is known for having granulomas with central necrosis, often in the respiratory tract and kidneys. The vasculitis affects small vessels, leading to the symptoms mentioned.
The options aren't listed, but common distractors might include features like non-caseating granulomas (like in sarcoidosis), caseating granulomas (Tuberculosis), or other types of vasculitis like Wegener's. Wait, GPA is also known as Wegener's granulomatosis. So the histological features would be granulomas with necrosis and vasculitis. The key here is the combination of granulomatous inflammation and necrotizing vasculitis in the same tissue.
Possible wrong options could be: A. Caseating granulomas (Tuberculosis), B. Non-caseating granulomas (Sarcoidosis), C. Lymphocytic infiltration (like in some autoimmune conditions), D. Fibrinoid necrosis (seen in other vasculitides like Henoch-Schönlein purpura). The correct answer would be a combination of granulomas and necrotizing vasculitis.
So the correct histological feature is granulomas with central necrosis and necrotizing vasculitis. The clinical pearl here is that GPA is characterized by this combination, which differentiates it from other vasculitides. Also, ANCA positivity (usually c-ANCA against PR3) is a key lab finding, but the question is about histology.
**Core Concept**
Granulomatosis with polyangitis (GPA), previously known as Wegener's granulomatosis, is a systemic autoimmune vasculitis characterized by **granulomatous inflammation** and **focal necrotizing vasculitis** affecting small- to medium-sized vessels. The histopathology typically involves **upper/lower respiratory tract** and **renal tissues**.
**Why the Correct Answer is Right**
The hallmark histological feature of GPA is the presence of **focal necrotizing granulomas** with **necrotizing vasculitis** in affected tissues. Granulomas are composed of **epithelioid histiocytes**, **multinucleated giant cells**, and **lymphocytes**, often with central necrosis. Vasculitis manifests as **fibrinoid necrosis of vessel walls** with neutrophilic infiltration, leading to ischemic damage in organs like the lungs (causing hemoptysis) and kidneys. This combination distinguishes GPA from other vasculitides.
**Why Each Wrong Option is Incorrect**
**Option A:** Caseating granulomas are specific to **tuberculosis** or **fungal infections**, not GPA.
**Option B:** Non-necrotizing granulomas with epithelioid cells and absence of necrosis are classic for **sarcoidosis**.
**Option C:** Lymphocytic