Case report: Thoracolumbar spinal stenosis associated with alkaptonuria

Alkaptonuria: Clinical Spectrum of a Diagnosed Case in Bahrain With a Literature Review

Alkaptonuria (AKU) is a rare metabolic condition caused by mutations within a gene coding for homogentisate 1,2 dioxygenase enzyme involved in the tyrosine catabolism pathway. This mutation will result in the accumulation of homogentisic acid (HGA) in the body. AKU is a multi-systemic slowly progressing disease. The onset of its clinical presentation may vary based on the extensive disposition of the HGA. Initially, it might be asymptomatic, and symptoms usually appear in the second or third decades due to the formation of HGA, melanin compounds that accumulate in the cartilage leading to ochronosis. Furthermore, by the fourth or fifth decade, ochronotic arthropathy occurs, along with other extra-articular complications such as cardiovascular manifestations (e.g., valvular heart disease), renal and prostatic stones, and hypothyroidism. Management of this condition is mainly symptomatic, focusing on the treatment of its complications. Recently, the use of nitisinone (NTBC) has shown stabilization of disease manifestations. In this report, we present in detail the first AKU-diagnosed patient, including the clinical presentations, radiological findings, genetic results, and clinical outcomes, from the main tertiary hospital in Bahrain. Moreover, we conducted a thorough literature review on this rare condition.

Disc-coloration of an ochronotic cervical intervertebral disc in a patient with alkaptonuria: Case report and review of the literature

OBJECTIVES

Alkaptonuria is a rare inborn disorder of phenylalanine and tyrosine metabolism. It is characterized by an accumulation of homogentisic acid and its oxidation products, possibly resulting into connective tissue damaging. "Ochronosis" is a main feature, which is characterized by tissue discoloration and even alkaptonuric arthropathy. Cervical spine involvement is exceptional and there is a paucity of reports on surgical interventions in these patients. We explored the literature concerning cervical spine involvement in patients with alkaptonuria.

PATIENTS AND METHODS

We performed a review of the literature, in which patients with alkaptonuric degenerative changes of the cervical spine were examined. Articles were obtained from MEDLINE. Search terms included: "cervical", "alkaptonuria", "alkaptonuric changes" and "black disc". Additional studies were identified by checking reference lists. Furthermore, we present the case of a 46 year old patient with critical cervical spinal canal stenosis who underwent C6-C7 anterior cervical microdiscectomy and interbody fusion, in order to prevent myelopathic changes. CARE statement guidelines were followed.

RESULTS

Peroperatively, we did not encounter any macroscopic abnormalities of the skin, muscles or ligaments. A black discoloration of the nucleus pulposus was observed. Peroperative and postoperative course was uneventful.

CONCLUSION

Alkaptonuric degenerative abnormalities most commonly involve the lumbar spine, although the cervical spine can be affected in rare cases. Most frequently, the diagnosis of alkaptonuria can be made based on the clinical phenotype many years before symptoms secondary to ochronotic arthropathy develop. A retrospective diagnosis based on peroperative black discoloration of spinal structures has been described. A black discoloration of the intervertebral disc should encourage the neurosurgeon to further explore the possibility of alkaptonuria, even in the absence of a clear phenotype. Surgical results are mostly satisfactory. Further studies are required in order to better understand this pathology and its postoperative course.

Molecular landscape of congenital vertebral malformations: recent discoveries and future directions

Vertebral malformations (VMs) pose a significant global health problem, causing chronic pain and disability. Vertebral defects occur as isolated conditions or within the spectrum of various congenital disorders, such as Klippel-Feil syndrome, congenital scoliosis, spondylocostal dysostosis, sacral agenesis, and neural tube defects. Although both genetic abnormalities and environmental factors can contribute to abnormal vertebral development, our knowledge on molecular mechanisms of numerous VMs is still limited. Furthermore, there is a lack of resource that consolidates the current knowledge in this field. In this pioneering review, we provide a comprehensive analysis of the latest research on the molecular basis of VMs and the association of the VMs-related causative genes with bone developmental signaling pathways. Our study identifies 118 genes linked to VMs, with 98 genes involved in biological pathways crucial for the formation of the vertebral column. Overall, the review summarizes the current knowledge on VM genetics, and provides new insights into potential involvement of biological pathways in VM pathogenesis. We also present an overview of available data regarding the role of epigenetic and environmental factors in VMs. We identify areas where knowledge is lacking, such as precise molecular mechanisms in which specific genes contribute to the development of VMs. Finally, we propose future research avenues that could address knowledge gaps.