What are the characteristic X ray findings for ochronosis?
Lumbosacral radiographs show premature degenerative changes, ligamentous calcifications that can resemble ankylosing spondylitis, dense wafer-like calcifications of the intervertebral discs, vacuum discs, and narrowing of the intervertebral spaces. Sacroiliac joints are normal. Prominent intervertebral disc calcification can also be seen in hemochromatosis, hyperparathyroidism, calcium pyrophosphate deposition disease, paralytic poliomyelitis, and amyloidosis. The radiographic appearance of the large peripheral joints in ochronotic arthritis is virtually indistinguishable from that in primary osteoarthritis. The elevated levels of HA and its oxidation byproduct cause cartilaginous tissue to become stiff and brittle, inhibit lysyl oxidase, which decreases collagen crosslinking, and are cytotoxic to chondrocytes resulting in premature osteoarthritis.
