Alkaptonuria—an atypical case: multi-modality imaging review

Alkaptonuria is a rare inborn metabolic disorder due to a mutation in the homogentisic acid oxidase enzyme (HGO) gene on chromosome 3q. As HGO is deficient in alkaptonuria patients, there is an accumulation of homogentisic acid in the blood and urine. Homogentisic acid gets deposited in the soft tissues, tendons, cartilages, large joints and intervertebral discs. Ochronosis usually affects the dorsolumbar spine and typically spares the cervical spine and sacroiliac joints. However, in this case of isolated ochronosis, we report co-existent extensive cervical spine degenerative changes and cervical vertebral fusion, which has not been described in the literature so far.