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Journal of Inherited Metabolic Disease Mar 2024Altered activity of specific enzymes in phenylalanine-tyrosine (phe-tyr) metabolism results in incomplete breakdown of various metabolite substrates in this pathway....
Altered activity of specific enzymes in phenylalanine-tyrosine (phe-tyr) metabolism results in incomplete breakdown of various metabolite substrates in this pathway. Increased biofluid concentration and tissue accumulation of the phe-tyr pathway metabolite homogentisic acid (HGA) is central to pathophysiology in the inherited disorder alkaptonuria (AKU). Accumulation of metabolites upstream of HGA, including tyrosine, occurs in patients on nitisinone, a licenced drug for AKU and hereditary tyrosinaemia type 1, which inhibits the enzyme responsible for HGA production. The aim of this study was to investigate the phe-tyr metabolite content of key biofluids and tissues in AKU mice on and off nitisinone to gain new insights into the biodistribution of metabolites in these altered metabolic states. The data show for the first time that HGA is present in bile in AKU (mean [±SD] = 1003[±410] μmol/L; nitisinone-treated AKU mean [±SD] = 45[±23] μmol/L). Biliary tyrosine, 3(4-hydroxyphenyl)pyruvic acid (HPPA) and 3(4-hydroxyphenyl)lactic acid (HPLA) are also increased on nitisinone. Urine was confirmed as the dominant elimination route of HGA in untreated AKU, but with indication of biliary excretion. These data provide new insights into pathways of phe-tyr metabolite biodistribution and metabolism, showing for the first time that hepatobiliary excretion contributes to the total pool of metabolites in this pathway. Our data suggest that biliary elimination of organic acids and other metabolites may play an underappreciated role in disorders of metabolism. We propose that our finding of approximately 3.8 times greater urinary HGA excretion in AKU mice compared with patients is one reason for the lack of extensive tissue ochronosis in the AKU mouse model.
PubMed: 38487984
DOI: 10.1002/jimd.12728 -
Nature Reviews. Disease Primers Mar 2024Alkaptonuria is a rare inborn error of metabolism caused by the deficiency of homogentisate 1,2-dioxygenase activity. The consequent homogentisic acid (HGA) accumulation... (Review)
Review
Alkaptonuria is a rare inborn error of metabolism caused by the deficiency of homogentisate 1,2-dioxygenase activity. The consequent homogentisic acid (HGA) accumulation in body fluids and tissues leads to a multisystemic and highly debilitating disease whose main features are dark urine, ochronosis (HGA-derived pigment in collagen-rich connective tissues), and a painful and severe form of osteoarthropathy. Other clinical manifestations are extremely variable and include kidney and prostate stones, aortic stenosis, bone fractures, and tendon, ligament and/or muscle ruptures. As an autosomal recessive disorder, alkaptonuria affects men and women equally. Debilitating symptoms appear around the third decade of life, but a proper and timely diagnosis is often delayed due to their non-specific nature and a lack of knowledge among physicians. In later stages, patients' quality of life might be seriously compromised and further complicated by comorbidities. Thus, appropriate management of alkaptonuria requires a multidisciplinary approach, and periodic clinical evaluation is advised to monitor disease progression, complications and/or comorbidities, and to enable prompt intervention. Treatment options are patient-tailored and include a combination of medications, physical therapy and surgery. Current basic and clinical research focuses on improving patient management and developing innovative therapies and implementing precision medicine strategies.
Topics: Male; Humans; Female; Alkaptonuria; Quality of Life; Ochronosis; Kidney; Homogentisic Acid
PubMed: 38453957
DOI: 10.1038/s41572-024-00498-x -
Journal of Orthopaedic Case Reports Feb 2024Alkaptonuria is a rare autosomal recessive disorder caused by the defective metabolism of homogentisic acid, with a rare course and remained undetected even until...
INTRODUCTION
Alkaptonuria is a rare autosomal recessive disorder caused by the defective metabolism of homogentisic acid, with a rare course and remained undetected even until adulthood. Ochronotic arthropathy is one of the manifestations of alkaptonuria, predominantly affecting weight bearing joints such as spine, hip, and knee. Total joint arthroplasty is treatment of choice in end-stage arthritis of hip and knee. Owing to the rarity of the disease, limited data is available in literature regarding surgical challenges and long-term functional outcomes.
CASE REPORT
Herein, we present a case of 43-year-old male with ochronotic arthropathy of bilateral hip, right knee, and bilateral elbow joints with involvement of spine, who was incidentally diagnosed with ochronotic arthropathy intraoperatively and underwent sequential arthroplasty for right hip followed by right knee and left hip over a period of 10 years. At 11 years' follow-up, the patient has full mobility with no loosening of implants.
CONCLUSION
The long-term results of total joint arthroplasty in ochronotic arthropathy are good. Surgeon should be aware of the difficulty in soft tissue balancing and possible complications in the ochronotic arthropathy and require a conscientious approach to avoid complications.
PubMed: 38420236
DOI: 10.13107/jocr.2024.v14.i02.4224 -
European Heart Journal. Case Reports Feb 2024Alkaptonuria is a rare metabolic disease that causes an increase in homogentisic acid (HGA) due to a lack of enzymatic activity. Commonly, accumulation of HGA presents...
BACKGROUND
Alkaptonuria is a rare metabolic disease that causes an increase in homogentisic acid (HGA) due to a lack of enzymatic activity. Commonly, accumulation of HGA presents with dark discoloration of skin and other tissues, also known as ochronosis. Additionally, alkaptonuria can result in other clinical manifestations, including arthritis and cardiac disease. This case highlights alkaptonuria-related cardiac disease and challenges that cardiac surgery teams may face when treating this patient population.
CASE SUMMARY
A 62-year-old male with a history of alkaptonuria, Hodgkin's lymphoma treated with chemoradiation, hypertension, and hyperlipidaemia originally presented with shortness of breath in the setting of known cardiac disease. Cardiac work-up demonstrated aortic stenosis, mitral stenosis, and multivessel coronary artery disease requiring aortic valve replacement, mitral valve replacement, and coronary artery bypass grafting. During the operation, significant discoloration of tissue was observed. This correlated with areas of severe calcification, which was noted throughout both valves. Extensive debridement was required prior to proceeding to valve replacements. Additionally, near-infrared spectroscopy failed to provide accurate measurements of cerebral oxygenation.
DISCUSSION
Alkaptonuria is correlated with cardiovascular disease, particularly valvular disease. Intraoperatively, these patients may exhibit noticeable discoloration and severe calcification of various tissues. Additionally, traditional infrared-based methods of cerebral oxygenation monitoring may not be reliable; however, other options of cerebral monitoring may be feasible. With proper pre-operative planning, however, patients with alkaptonuria may safely undergo cardiac surgery.
PubMed: 38405194
DOI: 10.1093/ehjcr/ytae076 -
The New England Journal of Medicine Jan 2024
Topics: Humans; Ochronosis; Skin Cream; Skin Lightening Preparations
PubMed: 38231626
DOI: 10.1056/NEJMicm2305739 -
Cureus Nov 2023Exogenous ochronosis (EO) results as a complication of long-term usage of skin lightening creams containing hydroquinone or other bleaching agents. Duration of use and...
Exogenous ochronosis (EO) results as a complication of long-term usage of skin lightening creams containing hydroquinone or other bleaching agents. Duration of use and concentration of hydroquinone in the product are noted to be key factors that decide the occurrence of EO. With more cases being reported globally, current classification systems lack practical applicability and may not be adequate for detecting early cases. Dermoscopy and clinicopathological correlation are very important for early diagnosis of EO to avoid undue overuse of hydroquinone leading to further deterioration of pigmentation. We report a series of six patients in one year with EO with the minimum duration of use of hydroquinone being three months to the development of ochronosis. The most common strength of hydroquinone used was 2%, documented in 5/6 cases. Three out of six patients (50%) had discordant findings according to the Dogliotti classification, while four out of six patients (66.7%) had discordant findings according to the Phillips classification. Our findings suggest that EO can occur with a shorter duration of hydroquinone use, even at lower percentage strengths. We propose that it may be more useful to accept the clinical presentation supported by dermoscopic features as adequate actionable findings, consider all the histopathological stages as warning signs of ochronosis or impending ochronosis, and terminate the use of hydroquinone in such patients.
PubMed: 38161945
DOI: 10.7759/cureus.49620 -
Cureus Oct 2023Alkaptonuria is a rare genetic disorder characterized by the excessive production of homogentisic acid, leading to the formation and deposition of pigment polymers...
Alkaptonuria is a rare genetic disorder characterized by the excessive production of homogentisic acid, leading to the formation and deposition of pigment polymers throughout the body. It is extremely rare, affecting only around one in 100,000 individuals. Despite the normal life expectancy, it can cause severe morbidities. Alkaptonuria is typically managed supportively with pain medication, dietary modifications, and surgical interventions, which are considered to be the gold standard of therapy. Here we present a case of a 33-year-old male with no previous medical or surgical history who presented with severe acute back pain radiating to the left leg. Genetic testing confirmed a homozygous pathogenic variant for alkaptonuria. This case highlights the challenges in diagnosing alkaptonuria, emphasizing the significance of early detection, and clinical evaluation for improved outcomes. Furthermore, it underscores the need to consider alkaptonuria as a multidimensional disease, necessitating further research to enhance our understanding and develop effective management. Therefore, this study serves as an opportunity for future trials and studies aimed at digging deeper into the intricacies of alkaptonuria to increase our understanding and establish comprehensive management plans for affected individuals.
PubMed: 37937039
DOI: 10.7759/cureus.46644 -
Biomedicines Sep 2023Endogenous ochronosis, also known as alkaptonuria, is a rare disease known for its bluish-black discoloration of the skin, sclerae, and pinnae, as well as urine that...
Endogenous ochronosis, also known as alkaptonuria, is a rare disease known for its bluish-black discoloration of the skin, sclerae, and pinnae, as well as urine that turns black upon standing. Though rarely fatal, joint degradation is a common sequela, and many patients require multiple large joint arthroplasties throughout their lifetime. Though many aspects of the pathophysiological mechanisms of the disease have been described, questions remain, such as how the initiation of ochronotic pigmentation is prompted and the specific circumstances that make some tissues more resistant to pigmentation-related damage than others. In this report, we present the case of an 83-year-old female previously diagnosed with alkaptonuria including high-quality arthroscopic images displaying the fraying of articular cartilage. We also offer a summary of the latest literature on the pathophysiological mechanisms of the disease, including cellular-level changes observed in ochronotic chondrocytes, biochemical and mechanical alterations to the cartilaginous extracellular matrix, and patterns of pigmentation and joint degradation observed in humans and mice models. With these, we present an overview of the mechanisms of ochronotic chondropathy and joint degradation as the processes are currently understood. While alkaptonuria itself is rare, it has been termed a "fundamental disease," implying that its study and greater understanding have the potential to lead to insights in skeletal biology in general, as well as more common pathologies such as osteoarthritis and their potential treatment mechanisms.
PubMed: 37892999
DOI: 10.3390/biomedicines11102625 -
BMJ Case Reports Oct 2023Alkaptonuria is a very rare disorder in which homogentisic acid accumulates due to a deficiency in the activity of homogentisic acid 1,2 dioxygenase. This deficiency...
Alkaptonuria is a very rare disorder in which homogentisic acid accumulates due to a deficiency in the activity of homogentisic acid 1,2 dioxygenase. This deficiency results in deposition of a yellowish-brown pigment in connective tissue. Such deposition is termed 'ochronosis' and leads to deterioration in the formation and structure of proteoglycans in hyaline cartilage. These actions lead to fragmentation and rapid destructive arthritis. Often, ochronotic arthritis appears at 40-60 years of age, and many patients are treated symptomatically. Here, we report two patients (three ankles) with ochronotic arthritis who were treated with ankle arthrodesis. In all cases, the postoperative clinical score improved, but the time needed for fusion was prolonged and symptomatic subtalar arthropathy developed in the early postoperative period.
Topics: Humans; Alkaptonuria; Ankle; Homogentisic Acid; Osteoarthritis; Cartilage Diseases; Arthrodesis
PubMed: 37880174
DOI: 10.1136/bcr-2022-254300 -
Frontiers in Medicine 2023Ochronosis is a rare autosomal recessive disorder of tyrosine metabolism characterized by multilevel spinal degeneration and arthritis of large weight-bearing joints,...
Ochronosis is a rare autosomal recessive disorder of tyrosine metabolism characterized by multilevel spinal degeneration and arthritis of large weight-bearing joints, which is referred to as ochronotic arthropathy. In this case report, we describe diagnosis and treatment of ochronotic arthropathy in a patient who underwent total hip arthroplasty (THA) and total knee arthroplasty (TKA). The Harris hip score was 26 preoperatively and 45, 68, 76, 90, 92, and 94 at 1, 3, 6, 9, 11, and 14 months, respectively, postoperatively. The forgotten joint score (FJS) of the hip was 27.8, 52.8, 81.1, 89.0, 90.6, and 92.4 at 1, 3, 6, 9, 11, and 14 months, respectively, postoperatively. TKA was performed 8 months after THA. The Knee Society Score was 36 before TKA and 74, 82, and 90 at 1, 3, and 6 months, respectively, after TKA. The FJS of the knee was 36.6, 63.9, and 84.5 at 1, 3, and 6 months, respectively, after TKA. The patient's knee range of motion returned to normal, with significant reduction in pain and improved satisfaction levels after TKA. THA and TKA can achieve good clinical outcomes in patients with ochronosis accompanied by severe joint pain.
PubMed: 37795417
DOI: 10.3389/fmed.2023.1212580