Identification of an extraordinary bone phenotype in a patient with alkaptonuria

Abstract

Event Abstract Back to Event Identification of an extraordinary bone phenotype in a patient with alkaptonuria AM Taylor1*, JS Davidson2, JC Jarvis1, LR Ranganath1, JA Gallagher1 and A Boyde3 1 University of Liverpool, Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease, United Kingdom 2 Royal Liverpool and Broadgreen University Hospitals Trust, Department of Trauma & Orthopaedics, United Kingdom 3 Queen Mary University of London, Institute of Dentistry, United Kingdom A 59 year old man with known alkaptonuria (AKU) presented for surgery due to ochronotic osteoarthropathy and underwent a total hip replacement. The resected femoral head showed uniform ochronosis of the articular cartilage with the presence of a large osteophyte on the neck of femur, also demonstrating ochronosis. Surrounding capsular tissues displayed patchy ochronotic pigmentation. An ultrastructural and histological analysis of patient tissues was undertaken. Samples were processed for histology and for topographical 3D scanning electron microscopy (SEM) and quantitative back scattered electron SEM (qBSE-SEM). These analyses revealed an extraordinary phenotype including the presence of some novel microanatomical structures. Histological examination of the cartilage demonstrated the presence of ochronotic pigment throughout all zones of articular cartilage, both intra- and extracellularly. No similar pigmentation was observed in the calcified cartilage or bone matrices, but these latter tissues underwent significant structural modelling. Ochronosis was observed in osteoblasts, osteoclasts and osteocytes, with osteoclasts seen engulfing pigmented osteocytes from the bone matrix. The most striking feature was the resorption of subchondral bone and calcified cartilage such that in advanced stages there was complete loss of the subchondral bone plus calcified cartilage plate. The underlying trabecular bone also contained idiosyncratic architecture. Trabecular surfaces had numerous outgrowths that we have termed 'excrescences' of which three distinct types were recognized. The first type arose from the incomplete resorption of branching trabeculae and they were characterized by scalloped surfaces and rugged edges. The second type arose in a similar way but had been smoothed over by new bone deposition. The third type which resembled coarse stucco probably arose from resting surfaces that had been focally reactivated. These were poorly cemented to the prior trabecular wall. They had a disorganized arrangement of collagen fibres and contained poorly mineralised and hypermineralised regions. We propose these distinctive microanatomical structures do not arise as a result of pigmentation per se but because of abnormal osteoclast/osteoblast modelling secondary to altered mechanical loading or other aberrant signalling. The distinctive subchondral environment underneath pigmented cartilage in AKU provides a unique model to investigate the response of bone to altered mechanical loading. Keywords: Bones, Bone Research Conference: 2011 joint meeting of the Bone Research Society & the British Orthopaedic Research Society, Cambridge, United Kingdom, 27 Jun - 29 Jun, 2011. Presentation Type: Poster Topic: Abstracts Citation: Taylor A, Davidson J, Jarvis J, Ranganath L, Gallagher J and Boyde A (2011). Identification of an extraordinary bone phenotype in a patient with alkaptonuria. Front. Endocrinol. Conference Abstract: 2011 joint meeting of the Bone Research Society & the British Orthopaedic Research Society. doi: 10.3389/conf.fendo.2011.02.00067 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 30 Sep 2011; Published Online: 30 Sep 2011. * Correspondence: Dr. AM Taylor, University of Liverpool, Department of Musculoskeletal Biology, Institute of Ageing and Chronic Disease, Liverpool, United Kingdom, amtaylor@liv.ac.uk Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers AM Taylor JS Davidson JC Jarvis LR Ranganath JA Gallagher A Boyde Google AM Taylor JS Davidson JC Jarvis LR Ranganath JA Gallagher A Boyde Google Scholar AM Taylor JS Davidson JC Jarvis LR Ranganath JA Gallagher A Boyde PubMed AM Taylor JS Davidson JC Jarvis LR Ranganath JA Gallagher A Boyde Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.