**Core Concept**
Henoch Schonlein Purpura (HSP) is a form of vasculitis that primarily affects small vessels, characterized by the deposition of IgA immune complexes. This condition often presents with a tetrad of symptoms: palpable purpura, abdominal pain, arthritis, and renal involvement.

**Why the Correct Answer is Right**
Thrombocytopenia is not a characteristic finding in Henoch Schonlein Purpura. The condition is not caused by a platelet disorder or a problem with platelet aggregation. Instead, the presence of immune complexes leads to inflammation and damage to the blood vessel walls, resulting in the characteristic purpura. The normal platelet count in HSP patients helps to differentiate it from other conditions that may present with thrombocytopenia.

**Why Each Wrong Option is Incorrect**
**Option A:** Palpable purpura is a hallmark feature of Henoch Schonlein Purpura, often presenting as purpuric lesions on the lower extremities, buttocks, and sometimes on the face.

**Option B:** Nephritis is a potential complication of HSP, often presenting as hematuria, proteinuria, or both. It is believed to result from the deposition of IgA immune complexes in the renal glomeruli.

**Option D:** Abdominal pain is a common symptom in HSP, often presenting as colicky pain in the abdomen, which may be accompanied by gastrointestinal bleeding.

**Clinical Pearl / High-Yield Fact**
In addition to the classic tetrad of symptoms, patients with Henoch Schonlein Purpura may also experience gastrointestinal bleeding, which can be a significant complication. It is essential to monitor patients for signs of gastrointestinal involvement, particularly in those with significant abdominal pain.

**✓ Correct Answer: C. Thrombocytopenia**