Confusion of roentgenographic differential diagnosis between ankylosing hyperostosis (Forestier's disease) and ankylosing spondylitis

Diffuse Idiopathic Skeletal Hyperostosis (DISH) and a Possible Inflammatory Component

PURPOSE OF REVIEW

Diffuse Idiopathic Skeletal Hyperostosis (DISH) is considered a metabolic condition, characterized by new bone formation affecting mainly at entheseal sites. Enthesitis and enthesopathies occur not only in the axial skeleton but also at some peripheral sites, and they resemble to some extent the enthesitis that is a cardinal feature in spondyloarthritis (SpA), which is an inflammatory disease.

RECENT FINDINGS

We review the possible non-metabolic mechanism such as inflammation that may also be involved at some stage and help promote new bone formation in DISH. We discuss supporting pathogenic mechanisms for a local inflammation at sites typically affected by this disease, and that is also supported by imaging studies that report some similarities between DISH and SpA. Local inflammation, either primary or secondary to metabolic derangements, may contribute to new bone formation in DISH. This new hypothesis is expected to stimulate further research in both the metabolic and inflammatory pathways in order to better understand the mechanisms that lead to new bone formation. This may lead to development of measures that will help in earlier detection and effective management before damage occurs.

Magnetic resonance imaging in diffuse idiopathic skeletal hyperostosis: similarities to axial spondyloarthritis

Diffuse idiopathic skeletal hyperostosis (DISH) is a non-inflammatory condition that involves calcification and ossification of the spinal ligaments and entheses. While, characteristic magnetic resonance imaging (MRI) lesions of the spine in patients with axial spondyloarthritis, another enthesitis-related disease, have been described and defined, there is a paucity of information regarding the MRI findings in DISH. The aim of this study was to describe the MRI findings of patients with DISH. We collected computed tomography studies with findings characteristic of DISH and that also had corresponding and concurrent MRI studies of the spine. For each patient, sagittal T1-weighted and STIR MRI sequences were evaluated for anterior/posterior vertebral corners of bone marrow edema (BME) and fat deposition. In total, we assessed 156 vertebral units in 10 patients that had both radiographic evidence of DISH and available MRI studies of the spine. Lesions consistent with BME corners were detected in five patients, and in three of them, three separate sites were involved, a finding that is suggestive of axial spondyloarthritis (SpA) according to the ASAS/OMERACT consensus statement. Fat deposition corners were detected in eight patients and in seven of them, several sites were involved. Spinal MRI lesions that are characteristic of axial SpA were commonly observed in a cohort of patients with DISH. This bears relevance to cases with diagnostic uncertainty and may imply overlapping pathogenetic mechanisms for new bone formation in both SpA and DISH. Further study is indicated to better characterize the similarities and differences between the MRI lesions of DISH and SpA.

Whole Body Magnetic Resonance Imaging Features in Diffuse Idiopathic Skeletal Hyperostosis in Conjunction with Clinical Variables to Whole Body MRI and Clinical Variables in Ankylosing Spondylitis

OBJECTIVE

Discrimination of diffuse idiopathic skeletal hyperostosis (DISH) and ankylosing spondylitis (AS) can be challenging. Usefulness of whole-body magnetic resonance imaging (WB-MRI) in diagnosing spondyloarthritis has been recently proved. We assessed the value of clinical variables alone and in combination with WB-MRI to distinguish between DISH and AS.

METHODS

Diagnostic case-control study: 33 patients with AS and 15 patients with DISH were included. All patients underwent 1.5 Tesla WB-MRI scanning. MR scans were read by a blinded radiologist using the Canadian-Danish Working Group's recommendation. Imaging and clinical variables were identified using the bootstrap. The most important variables from MR and clinical history were assessed in a multivariate fashion resulting in 3 diagnostic models (MRI, clinical, and combined). The discriminative capacity was quantified using the area under the receiver-operating characteristic (ROC) curve. The strength of diagnostic variables was quantified with OR.

RESULTS

Forty-eight patients provided 1545 positive findings (193 DISH/1352 AS). The final MR model contained upper anterior corner fat infiltration (32 DISH/181 AS), ankylosis on the vertebral endplate (4 DISH/60 AS), facet joint ankylosis (4 DISH/49 AS), sacroiliac joint edema (11 DISH/91 AS), sacroiliac joint fat infiltration (2 DISH/114 AS), sacroiliac joint ankylosis (2 DISH/119 AS); area under the ROC curve was 0.71, 95% CI 0.64-0.78. The final clinical model contained patient's age and body mass index (area under the ROC curve 0.90, 95% CI 0.89-0.91). The full diagnostic model containing clinical and MR information had an area under the ROC curve of 0.93 (95% CI 0.92-0.95).

CONCLUSION

WB-MRI features can contribute to the correct diagnosis after a thorough conventional workup of patients with DISH and AS.

Ankylosing Spondylitis: A Contemporary Perspective on Diagnosis and Treatment

OBJECTIVES

In recent years, great progress has been made in the development of diagnostic tools, therapeutic approaches, and validated outcome measures in the understanding of the pathogenesis of ankylosing spondylitis (AS). The purpose of this review was to summarize these developments.

METHODS

We performed a PubMed search for the period 1978 to 2005, using the keyword, "ankylosing spondylitis," resulting in a total of 4878 publications, including 778 reviews. Articles were then selected based on their discussion of recent diagnostic tools and new treatment approaches in the pathogenesis of AS, leading to a final total of 104 articles.

RESULTS

In recent years, there have been 2 major developments in the management of AS that make earlier diagnosis possible and offer the hope of alleviating pain and preventing structural changes that result in loss of function. These developments include the use of magnetic resonance imaging to visualize the inflammatory changes in the sacroiliac joint and the axial spine, and the demonstration that tumor necrosis factor blocking agents are highly efficacious in reducing spinal inflammation and possibly in slowing radiographic progression.

CONCLUSIONS

There have been major advances in both the diagnostic tools and the therapeutic regimens available for patients with AS.

[Ankylosing spondylitis--current state of imaging including scoring methods]

Conventional radiography and magnetic resonance imaging (MRI) are currently the most widely used imaging methods for the initial diagnostic evaluation and follow-up of patients with ankylosing spondylitis (AS). Scintigraphy, computed tomography (CT), and positron emission tomography (PET) only play minor roles, although some are being further developed. AS is characterized by inflammatory changes to the sacroiliac joints (SIJs) and spine, as well as asymmetrical arthritis of the peripheral joints and joints near the trunk. The diagnosis of AS is based on clinical parameters and the presence of chronic inflammatory changes to the SIJs on conventional radiographs. Typical radiographic changes also involve the spine. MRI depicts not only chronic changes, but also active inflammatory lesions, which are important for the diagnosis of early disease and precursors of AS. The scoring system of choice for quantifying spinal changes depicted by conventional radiography is the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS). MRI allows the quantitative evaluation of changes involving the SIJs and the spine. Various MRI scoring systems have been proposed to quantify these changes, but they require further validation. This review article presents the imaging modalities used in AS patients, typical findings, and relevant methods of analysis. The most recent developments are discussed.

Staging of patients with ankylosing spondylitis: a preliminary proposal

Patients with ankylosing spondylitis (AS) are characterised by a wide range of clinical presentations, radiographic profiles, and outcomes, which are not well differentiated by current diagnostic and classification systems for the disorder. Inadequacies in these systems may limit clinicians' ability to manage their patients with AS appropriately and act as an obstacle to reasonable comparison of therapeutic trial results. A standardised staging system for AS is therefore proposed that would provide a more detailed categorisation of patients based on assessment of structural damage, peripheral joint and organ involvement, presence of concomitant diseases, and the severity and extent of disease activity and functional impairment. The proposed system needs to be evaluated closely and amended as needed to assure its usefulness in clinical and research settings.

Diffuse idiopathic skeletal hyperostosis in Meroitic Nubians from Semna South, Sudan

The paleopathological study of human osteological remains from the site of Semna South, of northern Sudan, revealed that about thirteen percent of this ancient Nubian population had diffuse idiopathic skeletal hyperostosis (DISH). As in modern cases, males were more affected than females. Two thousand years ago, ancient Nubian males had the same spinal problems elderly men have today.

Seronegative spondyloarthropathies and diffuse idiopathic skeletal hyperostosis in ancient northern Chile

Bioarchaeological research of ancient Amerindians was undertaken to test the hypothesis that seronegative spondyloarthropathies (SNS) and diffuse idiopathic skeletal hyperostosis (DISH) existed in prehistoric South Americans. An osteological-radiographic model was developed from clinical literature and systematically applied to 504 archaeological human remains housed at the Universidad de Tarapacá in Arica, Chile, to search for evidence of these arthritides. The results showed that SNS existed with an average frequency of 7% for the adult sample and DISH averaged 4% in individuals over 40 years old. It was found that the antiquity of SNS date back at least 5,000 years in both New World and Old World populations. In contrast, the antiquity of DISH in the Americas is not clear because no previous studies have dealt with this subject; however, this research finds mild DISH cases dating back 4,000 years in northern Chile. It was also found that SNS and DISH exhibit a trend of increasing incidence with the advent of agro-pastoral activities and village formation.

Evaluation of the involvement of axial entheses and sacroiliac joints in relation to diagnosis: comparison among diffuse idiopathic skeletal hyperostostis (DISH), osteoarthrosis and ankylosing spondylitis

Since diffuse idiopathic skeletal hyperostosis (DISH) is frequently difficult to differentiate radiologically from the axial involvement of ankylosing spondylitis and osteoarthrosis, some features of these 3 different diseases were compared. The predominantly horizontal nature of the enthesiophyte in DISH and its right preponderance in the thoracic region were demonstrated. This right preponderance was due to the presence of the thoracic aorta located in the left thoracic side. A midthoracic notch was described in DISH which seemed to be confined to noninflammatory conditions, but was not found in ankylosing spondylitis. The importance of sacroiliac computerized tomography to differentiate sacroiliac joint abnormalities associated with DISH from the sacroiliitis of spondylarthropathies was stressed.

Coexistence of diffuse idiopathic skeletal hyperostosis and ankylosing spondylitis

To the best of our knowledge, only two patients with concurrent diffuse idiopathic skeletal hyperostosis (DISH) and ankylosing spondylitis (AS) have been reported so far. Here we present 3 patients in whom clinical and radiological findings indicative of DISH and AS coexisted. Two of these cases exhibited HLA B27. Although the presence of sacroiliitis would appear to exclude DISH, calcification and ossification of the anterior common vertebral ligament (ACVL) confirmed diagnosis of the latter disease.

Palaeopathology of spinal osteophytosis, vertebral ankylosis, ankylosing spondylitis, and vertebral hyperostosis

Five hundred and sixty intact skeletons and several thousand disarticulated vertebrae have been examined with special reference to spinal fusion. In period they ranged from a 21st dynasty Egyptian mummy to a mid-19th century skeleton. Osteophytes were found in about half of the specimens, as reported previously. Fifteen skeletons with extensive blocks of spinal fusion were also identified. Sacroiliitis was present in two, but the asymmetrical spinal disease and peripheral joint changes suggested Reiter's disease or psoriatic spondylitis rather than ankylosing spondylitis. The remaining 13 had typical features of Forrestier's disease, and extraspinal findings indicative of diffuse idiopathic skeletal hyperostosis (DISH) were also common. A review of the available literature suggests that many palaeopathological specimens previously reported as anklylosing spondylitis are examples of DISH or other seronegative spondylarthropathies. The antiquity and palaeopathology of AS needs reappraisal.