**Core Concept**
Bechterew disease, also known as ankylosing spondylitis, is a chronic inflammatory disease primarily affecting the axial skeleton and intervertebral joints, leading to eventual fusion of the vertebrae. This condition is characterized by a complex interplay between genetic predisposition and immune system dysregulation.

**Why the Correct Answer is Right**
The correct answer is related to the autoimmune nature of Bechterew disease. The condition is associated with the presence of HLA-B27 antigen, a specific human leukocyte antigen. The interaction between HLA-B27 and the immune system triggers an inflammatory response, resulting in the activation of various immune cells, including T cells and macrophages, which contribute to the disease's pathogenesis. The subsequent inflammation and fusion of the vertebrae are thought to be mediated by the production of pro-inflammatory cytokines, such as TNF-alpha.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe Bechterew disease.
**Option B:** This option is incorrect because it is a different condition altogether.
**Option C:** This option is incorrect because it is a characteristic feature of Bechterew disease, but not the disease itself.

**Clinical Pearl / High-Yield Fact**
Bechterew disease often presents with insidious onset and may initially be mistaken for mechanical low back pain. A high index of suspicion, particularly in young males with a family history of the disease, is essential for early diagnosis and initiation of appropriate treatment.

**Correct Answer: D. Bechterew disease**