**Core Concept**
Henoch-Schönlein purpura (HSP) is a form of vasculitis that primarily affects small blood vessels, leading to inflammation and bleeding into the skin and other organs. It is a type of IgA-mediated immune complex disease, characterized by the deposition of IgA immune complexes in the walls of small vessels.

**Why the Correct Answer is Right**
Henoch-Schönlein purpura typically presents with a classic tetrad of symptoms: non-thrombocytopenic purpura, abdominal pain, arthritis, and renal involvement. The purpura in HSP is caused by the deposition of IgA immune complexes in the dermal capillaries, leading to inflammation and bleeding. This process is mediated by the activation of complement and the release of various cytokines, which attract inflammatory cells to the affected area.

**Why Each Wrong Option is Incorrect**
**Option A:** While HSP can occasionally present with gastrointestinal symptoms, such as abdominal pain and gastrointestinal bleeding, it is not a defining characteristic of the disease.
**Option B:** Arthritis is a common manifestation of HSP, particularly affecting the knees, ankles, and wrists. It is a key component of the classic tetrad of symptoms.
**Option C:** Renal involvement is a serious complication of HSP, occurring in up to 50% of patients. It can range from mild hematuria to severe nephritic syndrome.

**Clinical Pearl / High-Yield Fact**
A key distinguishing feature of HSP is the presence of IgA deposits in the affected tissues, which can be demonstrated by immunofluorescence or immunohistochemistry. This is a critical diagnostic clue that helps differentiate HSP from other forms of vasculitis.

**Correct Answer: A.**