Ochronosis as an unusual cause of valvular defect: a case report

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.

Melanins as Sustainable Resources for Advanced Biotechnological Applications

Melanins are a class of biopolymers that are widespread in nature and have diverse origins, chemical compositions, and functions. Their chemical, electrical, optical, and paramagnetic properties offer opportunities for applications in materials science, particularly for medical and technical uses. This review focuses on the application of analytical techniques to study melanins in multidisciplinary contexts with a view to their use as sustainable resources for advanced biotechnological applications, and how these may facilitate the achievement of the United Nations Sustainable Development Goals.

"As Black as Ink": A Case of Alkaptonuria-Associated Myelopathy and a Review of the Literature

STUDY DESIGN

Case report and literature review.

OBJECTIVE

To characterize the rare presentation of myelopathy occurring secondary to alkaptonuria and to evaluate the available evidence regarding its treatment.

SUMMARY OF BACKGROUND DATA

Alkaptonuria is an autosomal recessive genetic condition with an estimated incidence of 1 in 250,000 to 1 in 1,000,000 people. Mutation of the enzyme homogentisate 1,2-dioxygenase leads to the production of high levels of homogentisic acid, with subsequent deposition in ligaments, cartilage, and menisci. Involvement of the spine is termed "ochronotic spondyloarthropathy," of which myelopathy is an uncommon presentation.

METHODS

We present the case of a 57-year-old man with alkaptonuria-associated myelopathy, who underwent surgical decompression. Ten additional cases were identified in the literature by a systematic search of PubMed and Google Scholar.

RESULTS

In a patient presenting with myelopathy, alkaptonuria may be suspected because of medical history, family history, symptoms (including darkened urine, pigmented ear cartilage, and sclera), or radiographic changes, such as multilevel disc collapse, progressive wafer-like disc calcification, extensive osteophyte formation, and spinal deformity. The diagnosis can be confirmed by urine homogentisic acid testing. Of the 11 patients presented here or identified in the literature, 2 were treated nonoperatively, 8 were treated with decompressive spinal surgery, and treatment of the myelopathy was not discussed for 1 patient. In all cases in which outcomes were reported, substantial improvement in the patient's condition was seen.

CONCLUSION

Alkaptonuria is a rare cause of myelopathy, but one that clinicians should understand. Although no disease-modifying treatment currently exists for alkaptonuria, the use of symptomatic treatments and, particularly, surgical decompression is recommended to address myelopathy if it develops.

LEVEL OF EVIDENCE

4.

Redox proteomics gives insights into the role of oxidative stress in alkaptonuria

Alkaptonuria (AKU) is an ultra-rare metabolic disorder of the catabolic pathway of tyrosine and phenylalanine that has been poorly characterized at molecular level. As a genetic disease, AKU is present at birth, but its most severe manifestations are delayed due to the deposition of a dark-brown pigment (ochronosis) in connective tissues. The reasons for such a delayed manifestation have not been clarified yet, though several lines of evidence suggest that the metabolite accumulated in AKU sufferers (homogentisic acid) is prone to auto-oxidation and induction of oxidative stress. The clarification of the pathophysiological molecular mechanisms of AKU would allow a better understanding of the disease, help find a cure for AKU and provide a model for more common rheumatic diseases. With this aim, we have shown how proteomics and redox proteomics might successfully overcome the difficulties of studying a rare disease such as AKU and the limitations of the hitherto adopted approaches.

Alkaptonuria in a middle-aged female

BACKGROUND

Alkaptonuria (AKU) or ochronosis is a rare progressive degenerative arthropathy that results from deficiency of enzyme homogentisate 1,2 dioxygenase (HGD). The features include arthritis of the spine and in larger peripheral joints, with chondrocalcinosis. In this paper, we present a case of alkaptonuria in a 54 year old woman in Tehran, Iran.

CASE PRESENTATION

A 54 year old woman with pain and limitation of motion in hip and lumbar spine was admitted in Firoozgar Hospital, Tehran. The problem began about 12 years ago with a history of darkening of urine and discoloration of sclera and ears. In imaging studies, there were degenerative changes in spine. In urine examination, the darkening of urine after exposure to air or bicarbonate found. Alkaptouria was confirmed by demonstrating an increased homogentisic acid (HGA) in urine. Her sister had back pain for a long period of time without response to therapy. She was subsequently diagnosed with alkaptonuria.

CONCLUSION

Alkaptonuria must be considered in the evaluation of low back pain of patients especially with having a positive family history and bluish discoloration of cartilage tissues.

Natural history of alkaptonuria revisited: analyses based on scoring systems

Increased circulating homogentisic acid in body fluids occurs in alkaptonuria (AKU) due to lack of enzyme homogentisate dioxygenase leading in turn to conversion of HGA to a pigmented melanin-like polymer, known as ochronosis. The tissue damage in AKU is due to ochronosis. A potential treatment, a drug called nitisinone, to decrease formation of HGA is available. However, deploying nitisinone effectively requires its administration at the most optimal time in the natural history. AKU has a long apparent latent period before overt ochronosis develops. The rate of change of ochronosis and its consequences over time following its recognition has not been fully described in any quantitative manner. Two potential tools are described that were used to quantitate disease burden in AKU. One tool describes scoring the clinical features that includes clinical assessments, investigations and questionnaires in 15 patients with AKU. The second tool describes a scoring system that only includes items obtained from questionnaires in 44 people with AKU. Analysis of the data reveals distinct phases of the disease, a pre-ochronotic phase and an ochronotic phase. The ochronotic phase appears to demonstrate an earlier slower progression followed by a rapidly progressive phase. The rate of change of the disease will have implications for monitoring the course of the disease as well as decide on the most appropriate time that treatment should be started for it to be effective either in prevention or arrest of the disease.

A quantitative assessment of alkaptonuria: testing the reliability of two disease severity scoring systems

Alkaptonuria (AKU) is due to excessive homogentisic acid accumulation in body fluids due to lack of enzyme homogentisate dioxygenase leading in turn to varied clinical manifestations mainly by a process of conversion of HGA to a polymeric melanin-like pigment known as ochronosis. A potential treatment, a drug called nitisinone, to decrease formation of HGA is available. However, successful demonstration of its efficacy in modifying the natural history of AKU requires an effective quantitative assessment tool. We have described two potential tools that could be used to quantitate disease burden in AKU. One tool describes scoring the clinical features that includes clinical assessments, investigations and questionnaires in 15 patients with AKU. The second tool describes a scoring system that only includes items obtained from questionnaires used in 44 people with AKU. Statistical analyses were carried out on the two patient datasets to assess the AKU tools; these included the calculation of Chronbach's alpha, multidimensional scaling and simple linear regression analysis. The conclusion was that there was good evidence that the tools could be adopted as AKU assessment tools, but perhaps with further refinement before being used in the practical setting of a clinical trial.

Cardiovascular manifestations of Alkaptonuria

The cardiovascular manifestations of alkaptonuria relate to deposition of ochronotic pigment within heart valves, endocardium, aortic intima and coronary arteries. We assessed 16 individuals with alkaptonuria for cardiovascular disease, including full electrocardiographic and echocardiographic assessment. The self reported prevalence of valvular heart disease and coronary artery disease was low. There was a significant burden of previously undiagnosed aortic valve disease, reaching a prevalence of over 40% by the fifth decade of life. The aortic valve disease was found to increase in both prevalence and severity with advancing age. In contrast to previous reports, we did not find a significant burden of mitral valve disease or coronary artery disease. These findings are important for the clinical follow-up of patients with alkaptonuria and suggest a role for echocardiographic surveillance of patients above 40 years old.

Identification of forty cases with alkaptonuria in one village in Jordan

Alkaptonuria (AKU) is one of the four initially identified inborn errors of metabolism. The prevalence of AKU is unknown in Jordan. Therefore, a research project was started in April 2009 at the Faculty of Medicine/Mutah University in southern Jordan. The aims of the project were to identify people with AKU, to screen all family members with history of AKU, and to increase the awareness about the disease among health care professionals and the community in southern Jordan. Targeted family screening method was used to identify patients with AKU. In this paper, we present preliminary results of screening 17 families with history of AKU in a single village in southern region of Jordan. Forty cases with AKU were identified in this village (age range, 1-60 years). Early cases with AKU were diagnosed through out this study, two-third of patients (n = 28) were under the age of thirty. Interestingly, nine cases with AKU were identified in one family. Our experience suggests that for the identification of cases with AKU where consanguinity is common, the focus for screening should be extended to all family members. The prevalence of AKU among Jordanian is likely to be greater than the prevalence rates worldwide due to high rates of consanguineous marriages. Further studies and effective screening programs are needed to detect undiagnosed cases of AKU, to provide genetic counseling, and ultimately to prevent the occurrence of new cases of AKU in Jordan.

Novel mutations in the homogentisate 1,2 dioxygenase gene identified in Jordanian patients with alkaptonuria

This study was conducted to identify mutations in the homogentisate 1,2 dioxygenase gene (HGD) in alkaptonuria patients among Jordanian population. Blood samples were collected from four alkaptonuria patients, four carriers, and two healthy volunteers. DNA was isolated from peripheral blood. All 14 exons of the HGD gene were amplified using the polymerase chain reaction (PCR) technique. The PCR products were then purified and analyzed by sequencing. Five mutations were identified in our samples. Four of them were novel C1273A, T1046G, 551-552insG, T533G and had not been previously reported, and one mutation T847C has been described before. The types of mutations identified were two missense mutations, one splice site mutation, one frameshift mutation, and one polymorphism. We present the first molecular study of the HGD gene in Jordanian alkaptonuria patients. This study provides valuable information about the molecular basis of alkaptonuria in Jordanian population.