**Question:** Hypersensitivity vasculitis is seen in-

A. Drug-induced vasculitis
B. Vasculitis due to infection
C. Vasculitis due to malignancy
D. Vasculitis due to autoimmune disorders

**Correct Answer:** D. Vasculitis due to autoimmune disorders

**Core Concept:**
Hypersensitivity vasculitis is a type of vasculitis (inflammation of blood vessels) that occurs in response to an autoimmune reaction (when the immune system mistakenly attacks the body's own tissues). There are five types of hypersensitivity reactions, classified based on the time course of the immune response: immediate (Type I), delayed (Type IV), and the intermediate types (Type II, III, and V). Hypersensitivity vasculitis falls under Type IV hypersensitivity reaction, also known as delayed hypersensitivity.

**Why the Correct Answer is Right:**
Hypersensitivity vasculitis occurs due to an immune response triggered by an autoantibody (antibody against the self) or autoreactive T cells attacking the blood vessels. This leads to inflammation, vessel wall damage, and the release of inflammatory mediators that cause the characteristic features of hypersensitivity vasculitis.

**Why Each Wrong Option is Incorrect:**

A. Drug-induced vasculitis (Type III hypersensitivity reaction): This type of vasculitis is caused by circulating immune complexes formed from drug-antibody complexes. It usually presents with a more widespread involvement and is distinct from hypersensitivity vasculitis.

B. Vasculitis due to infection (Type III hypersensitivity reaction): Infections can cause vasculitis through various mechanisms, such as bacterial endotoxins or immune complex formation, but it is not specific to Type IV hypersensitivity reaction.

C. Vasculitis due to malignancy (e.g., lymphoma): Although malignancies can cause vasculitis, the correct answer should specifically address Type IV hypersensitivity reaction.

D. Vasculitis due to autoimmune disorders: Hypersensitivity vasculitis is a type of autoimmune vasculitis, as it is triggered by autoantibodies or autoreactive T cells. Autoimmune disorders are broader than hypersensitivity vasculitis, but they share a similar pathogenesis involving immune-mediated inflammation.

**Clinical Pearl:** Hypersensitivity vasculitis is a clinical manifestation of autoimmune reactions, which can be triggered by medications, infections, or malignancies. Its key feature is the involvement of small and medium-sized blood vessels, leading to a characteristic clinical presentation. Correct diagnosis and differentiation from other vasculitides are essential for appropriate management and prognosis.