Ochronotic arthropathy of the spine limited to the thoracic section

Radiological evolution of spinal disease in alkaptonuria and the effect of nitisinone

Objectives

Ochronotic spondyloarthropathy represents one of the main clinical manifestations of alkaptonuria (AKU); however, prospective data and description of the effect of nitisinone treatment are lacking.

Methods

Patients with AKU aged 25 years or older were randomly assigned to receive either oral nitisinone 10 mg/day (N=69) or no treatment (N=69). Spine radiographs were recorded yearly at baseline, 12, 24, 36 and 48 months, and the images were scored for the presence of intervertebral space narrowing, soft tissue calcifications, vacuum phenomena, osteophytes/hyperostosis and spinal fusion in the cervical, thoracic and lumbosacral segment at each of the time points.

Results

At baseline, narrowing of the intervertebral spaces, the presence of osteophytes/hyperostosis and calcifications were the three most frequent radiographic features in AKU. The rate of progression of the five main features during the 4 years, ranked from the highest to lowest was as follows: intervertebral spaces narrowing, calcifications, vacuum phenomena, osteophytes/hyperostosis and fusions. The rate of progression did not differ between the treated and untreated groups in any of the five radiographic parameters except for a slower rate of progression (sum of all five features) in the treatment group compared with the control group (0.45 (1.11) nitisinone vs 0.74 (1.11) controls, p=0.049) in the thoracic segment.

Conclusion

The present study shows a relatively slow but significant worsening of radiographic features in patients with AKU over 4 years. Our results demonstrate a modest beneficial effect of 10 mg/day of nitisinone on the slowly progressing spondylosis in AKU during the relatively limited follow-up time.

Trial registration number

NCT01916382.

Characterizing the alkaptonuria joint and spine phenotype and assessing the effect of homogentisic acid lowering therapy in a large cohort of 87 patients

A large alkaptonuria (AKU) cohort was studied to better characterize the poorly understood spondyloarthropathy of rare disease AKU. Eighty-seven patients attended the National Alkaptonuria Centre (NAC) between 2007 and 2020. Seven only attended once. Fifty-seven attended more than once and received nitisinone 2 mg daily. Twenty-three attended at least twice without receiving nitisinone. Assessments included questionnaire analysis, ^18F Positron emission tomography computerised tomography (PETCT), as well as photographs of ochronotic pigment in eyes and ears at baseline when 2 mg nitisinone was commenced and yearly thereafter. Blood and urine samples were collected for chemical measurement. The prevalence of ochronosis, as well as pain, PETCT and combined pain and PETCT scores, was greatly increased at 90.5%, 85.7%, 100%, and 100%, respectively. Joint pain scores were greatest in proximal joints in upper and lower limbs. PETCT joint scores were higher in proximal joints in upper limb but higher in distal joints in the lower limb. Spine pain scores were highest in lumbar, followed by cervical, thoracic, and cervical regions at 77.4%, 59.5%, 46.4%, and 25%, respectively. PETCT spine scores were highest in thoracic followed by lumbar, cervical, and sacroiliac regions at 74.4%, 70.7%, 64.6%, and 47.8% respectively; ochronosis associated closely with spondyloarthropathy scores (R = .65; P < .0001). Nitisinone reversed ochronosis significantly, with a similar pattern of decreased joint and spine disease. Spondyloarthropathy is a highly prevalent feature in this NAC cohort. Ochronosis appears to be associated with spondyloarthropathy. Nitisinone decreases ochronosis and had a similar nonsignificant effect pattern on spondyloarthropathy.

Symptomatic pseudarthrosis in ochronotic spine: case report

In this study the authors report the first example of spinal pseudarthrosis in a patient with ochronosis, and they describe the application of posterior-only 360° surgery as an alternative approach to combined anterior-posterior surgery in the management of pseudarthrosis of an ankylosed spine, regardless of its etiology. Spinal involvement in ochronosis produces loss of flexibility and ankylosis of thoracic and lumbar segments. Pseudarthrosis is a serious complication of the diseases that present with ankylosis of the spine. However, its occurrence in ochronotic spine has not been reported previously. Evaluation of progressive paraparesis in a 68-year-old man with ochronosis revealed pseudarthrosis at the T11-12 level. Circumferential dural sac decompression, debridement of the disc space, interbody fusion, and screw-rod fixation were all done via a posterior-only approach. Postoperatively the patient exhibited a marked recovery in terms of pain and neurological status. At the 3-month follow-up, he was able to walk independently. Ochronosis should be included in the etiology of pseudarthrosis. With aggravation of back pain and the appearance of neurological deficits in an already stable patient with any ankylosing disease, pseudarthrosis should be suspected. Furthermore, single-stage, 360°, posterior-only surgery may obviate the need for single-stage or staged anterior-posterior surgical intervention in patients with pseudarthrosis of the thoracic and lumbar spine.

Alkaptonuria-Associated Changes in Disc Degeneration: A Case Report

CASE

A thirty-nine-year-old man with alkaptonuria presented with low back pain. Imaging demonstrated lumbar scoliosis, extensive irregularities of end-plate vertebral margins, and Thompson Grade-V disc degeneration. Six months later, the patient returned with a herniated L2-L3 disc. Minimally invasive disc surgery was performed, and harvested disc tissue showed marked extracellular matrix changes and ochronotic pigment deposits.

CONCLUSION

Scattered previous literature is available regarding disc changes in alkaptonuria. Although rare, alkaptonuria appears to severely impact the disc as reflected by cellular and matrix inclusions that contribute to disc-cell pathology.