**Core Concept**
Henoch-Schönlein purpura (HSP) is a form of vasculitis characterized by IgA immune complex deposition, affecting small blood vessels and leading to skin, joint, and gastrointestinal symptoms.

**Why the Correct Answer is Right**
HSP is a classic example of IgA-mediated vasculitis, where IgA antibodies deposit in the walls of small blood vessels, triggering an inflammatory response. This results in the characteristic non-thrombocytopenic purpura, abdominal pain, and joint inflammation. The deposition of IgA in the affected tissues is a hallmark of the disease.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not specify the involvement of IgA immune complexes, which is a key pathophysiological mechanism in HSP.
**Option B:** This option is incorrect as it does not accurately describe the clinical presentation of HSP, which typically involves purpura, abdominal pain, and joint inflammation, rather than just a single symptom.
**Option C:** This option is incorrect as it refers to a different condition, Henoch-Schönlein nephritis, which is a complication of HSP but not the primary diagnosis.

**Clinical Pearl / High-Yield Fact**
HSP is more common in children and often follows a viral upper respiratory tract infection, highlighting the importance of considering a preceding infection in the clinical history.

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