Ochronosis, Black Urine

Ochronosis is an autosomal recessive disorder (Figure 1) which cause problems with enzymes. With autosomal dominant inheritance, there will be structural problems.

Ochronosis will present itself to the patient as degenerative arthritis and low back pain (Figure 2).

The term associated with ochronosis is alkaptonuria, which is black urine and black bone disease (Figure 3). In this disorder, the homogentisic acid oxidase enzyme is defective and extra homogentisic acid deposits into the joints, leading to chondrocalcinosis. When the homogentisic acid deposits become polymerized it leads to early arthritis (Figure 4).

Patients can also develop spondylitis with degenerative changes, disc space narrowing, and calcification.

There can be a darkened, pigmented, full-thickness defect in the cartilage and a darkened synovium (Figure 5).

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