**Core Concept**
Vasculitis refers to the inflammation of blood vessels, which can be caused by various factors such as autoimmune disorders, infections, or exposure to certain medications. In adults, certain types of vasculitis are more common than others, while some are relatively rare.

**Why the Correct Answer is Right**
The correct answer is Henoch-Schönlein purpura (HSP), a form of vasculitis that primarily affects small blood vessels. HSP is characterized by the deposition of immune complexes containing IgA antibodies, which leads to inflammation and damage to the blood vessel walls. This condition is more commonly seen in children than in adults.

**Why Each Wrong Option is Incorrect**
**Option A:** Polyarteritis nodosa (PAN) is a form of vasculitis that affects medium-sized blood vessels and is more common in adults. PAN is characterized by the presence of granulomas and necrotizing inflammation of the blood vessel walls.
**Option B:** Giant cell arteritis (GCA) is a form of vasculitis that affects large blood vessels, particularly the temporal arteries, and is more common in adults. GCA is characterized by the presence of giant cells and granulomatous inflammation of the blood vessel walls.
**Option C:** Kawasaki disease is a form of vasculitis that primarily affects children, particularly those under the age of 5. It is characterized by the presence of fever, rash, and lymphadenopathy, as well as inflammation of the blood vessel walls.

**Clinical Pearl / High-Yield Fact**
HSP is often associated with abdominal pain, joint pain, and skin purpura, and can be triggered by upper respiratory tract infections. It is essential to consider HSP in the differential diagnosis of children and young adults presenting with these symptoms.

**Correct Answer: D. Henoch-Schönlein purpura**