Ochronosis and lumbar disc herniation - A case report and literature review

Background

Alkaptonuria (AKU) is a rare autosomal recessive disease characterized by a deficiency in an enzyme involved in the tyrosine and phenylalanine degradation. Patients suffering from this disorder develop a black coloration of cartilages known as ochronosis, leading to debilitating cartilage and arthritis at early ages. The spine is commonly involved but reports of lumbar disc disease are rare.

Methods

We present a case of a lumbar disc herniation secondary to ochronosis, and we also provide a comparative analysis with other cases documented in the literature. For the literature search we selected manuscripts published in PubMed, Embase, Scopus, Ovid, and Science Direct between 1963 and 2022.

Results

The mean age of the 25 included patients was 44.2 years (range: 22–69), and most of them were males (n = 19). The most common presentations were back pain and leg pain (n = 10), followed by lumbar radiculopathy (n = 9). Cauda equina syndrome (n = 2), thoracic myelopathy (n = 2), and cervical radiculopathy (n = 1) were less frequently observed. The lumbar region was the most affected area, with L4-L5 being the most affected level (n = 7), followed by L5-S1 (n = 4).

Conclusion

AKU can lead to ochronotic spondyloarthropathy and, rarely, disc herniation, particularly in the lower lumbar region. Surgeons should note that black cartilage during a discectomy indicates likely ochronotic disc involvement. Diagnosis requires histopathologic and biochemical analyses of blood and urine, usually done retrospectively. Genetic confirmation is crucial due to the multisystem nature of alkaptonuria. Our case contributes to the literature on this rare condition, emphasizing the need for comprehensive diagnostics.