**Core Concept**
Ochronosis is a condition characterized by the accumulation of homogentisic acid in connective tissues, primarily due to a defect in the enzyme homogentisate dioxygenase. This leads to increased deposition of dark pigment in cartilage and ligaments, particularly affecting the vertebral column and joints.

**Why the Correct Answer is Right**
In ochronosis, homogentisic acid accumulates and causes abnormal deposition in the intervertebral discs, leading to **calcification of the disc**. This calcification results in stiffness, pain, and structural changes in the spine. The disc material becomes brittle and may show radiographic evidence of calcification, which is a hallmark of this disorder. This is distinct from other spinal deformities like kyphosis or spondylolisthesis.

**Why Each Wrong Option is Incorrect**
Option B: *Bamboo spine* refers to the appearance of vertebrae with multiple, sharp, bamboo-like ridges, seen in **ankylosing spondylitis**, not ochronosis.
Option C: *Increased disc space* is observed in degenerative disc disease or early disc herniation, not in ochronosis.
Option D: *None* is incorrect because calcification of the disc is a well-documented radiographic feature in ochronosis.

**Clinical Pearl / High-Yield Fact**
Ochronosis is a rare, inherited disorder (homogentisic aciduria) that presents with joint pain, stiffness, and **early disc calcification**—a key radiological clue. It is often misdiagnosed as degenerative disease, so recognizing this pigment deposition is critical.

✓ Correct Answer: A. Calcification of disc