**Core Concept**
Thromboangitis obliterans, also known as Buerger's disease, is a rare, non-atherosclerotic, inflammatory disease affecting the small to medium-sized arteries and veins. It primarily affects the limbs, leading to ischemia and gangrene.

**Why the Correct Answer is Right**
The correct answer is **Arterial thickening**. This is because Thromboangitis obliterans is characterized by inflammation and thrombosis of the blood vessels, which leads to intimal thickening due to fibrosis and proliferation of smooth muscle cells. The disease process involves inflammation of the vessel walls, which can result in fibrosis and thickening of the arterial walls.

**Why Each Wrong Option is Incorrect**
**Option A:** Intimal hyperplasia is a feature of many vascular diseases, including atherosclerosis and restenosis after angioplasty, but it is not a unique characteristic of Thromboangitis obliterans.

**Option B:** Panarteritis is indeed a feature of Thromboangitis obliterans, as the disease involves inflammation of the entire vessel wall.

**Option C:** Vasospasm is a transient, reversible constriction of blood vessels, whereas the vasculature in Thromboangitis obliterans is characterized by chronic inflammation and fibrosis.

**Option D:** As explained earlier, arterial thickening is indeed a feature of Thromboangitis obliterans.

**Clinical Pearl / High-Yield Fact**
Thromboangitis obliterans is strongly associated with smoking, and patients with this disease often have a history of heavy tobacco use. It is essential to advise patients with this disease to quit smoking to prevent progression of the disease.

**✓ Correct Answer:** D. Arterial thickening