Large vessel vasculitides

Large-Vessel Vasculitis in Ophthalmology: Giant Cell Arteritis and Takayasu Arteritis

ABSTRACT

Giant cell arteritis and Takayasu arteritis are large-vessel vasculitides that share multiple common features but also have significant differences in epidemiology, demographics, clinical presentation, evaluation, and treatment. Giant cell arteritis is more common in elderly patients of Caucasian descent versus Takayasu arteritis, which is more prevalent in younger patients of Asian descent. Although traditionally age has been the main criterion for differentiating the 2 etiologies, modifications in the diagnostic criteria have recognized the overlap between the 2 conditions. In this monograph, we review the diagnostic criteria for both conditions and describe the epidemiology, pathogenesis, histology, evaluation, and management for large-vessel vasculitis in ophthalmology. Additionally, we describe ocular imaging techniques that may be utilized by ophthalmologists to identify manifestations of large-vessel vasculiti- des in patients. Lastly, we compare and contrast the key clinical, laboratory, and pathologic features that might help ophthalmologists to differentiate the 2 entities.

Ascending Aortic Aneurysm Secondary to Isolated Noninfectious Ascending Aortitis

Isolated noninfectious ascending aortitis (I-NIAA) is increasingly diagnosed at histopathologic review after resection of an ascending aortic aneurysm. PubMed was searched using the term aortitis; publications addressing the issue were reviewed, and reference lists of selected articles were also reviewed. Eleven major studies investigated the causes of an ascending aortic aneurysm or dissection requiring surgical repair: the prevalence of noninfectious aortitis ranged from 2% to 12%. Among 4 studies of lesions limited to the ascending aorta, 47% to 81% of cases with noninfectious aortitis were I-NIAA, more frequent than Takayasu arteritis or giant cell arteritis. Because of its subclinical nature and the lack of "syndromal signs" as in Takayasu arteritis or giant cell arteritis, I-NIAA is difficult to diagnose before complications occur, such as an aortic aneurysm or dissection. Therefore, surgical specimens of dissected aortic tissue should always be submitted for pathologic review. Diagnostic certainty requires the combination of a standardized histopathologic and clinical investigation. This review summarizes the current knowledge on I-NIAA, followed by a suggested approach to diagnosis, management, and follow-up. An illustrative case of an uncommon presentation is also presented. More follow-up studies on I-NIAA are needed, and diagnosis and follow-up of I-NIAA may benefit from the development of diagnostic biomarkers.

Magnetic resonance angiography versus 18F-fluorodeoxyglucose positron emission tomography in large vessel vasculitis

With advances in our understanding of the pathogenesis of large vessel vasculitides, we recognise the persistence of inflammation in large vessels, sometimes despite therapy to control clinical symptoms. Achieving an early diagnosis and establishing the extent of disease are important steps in improving our management of these diseases. Imaging is playing an increasing role in the assessment of these patients from diagnosis to prognosis. We review the current and potential role of two important and potentially complementary imaging techniques of magnetic resonance angiography and 18F-fluorodeoxyglucose positron emission tomography in the evaluation of patients with giant cell arteritis and Takayasu arteritis.

Analysis of the common genetic component of large-vessel vasculitides through a meta-Immunochip strategy

Giant cell arteritis (GCA) and Takayasu’s arteritis (TAK) are major forms of large-vessel vasculitis (LVV) that share clinical features. To evaluate their genetic similarities, we analysed Immunochip genotyping data from 1,434 LVV patients and 3,814 unaffected controls. Genetic pleiotropy was also estimated. The HLA region harboured the main disease-specific associations. GCA was mostly associated with class II genes (HLA-DRB1/HLA-DQA1) whereas TAK was mostly associated with class I genes (HLA-B/MICA). Both the statistical significance and effect size of the HLA signals were considerably reduced in the cross-disease meta-analysis in comparison with the analysis of GCA and TAK separately. Consequently, no significant genetic correlation between these two diseases was observed when HLA variants were tested. Outside the HLA region, only one polymorphism located nearby the IL12B gene surpassed the study-wide significance threshold in the meta-analysis of the discovery datasets (rs755374, P = 7.54E-07; OR_GCA = 1.19, OR_TAK = 1.50). This marker was confirmed as novel GCA risk factor using four additional cohorts (P_GCA = 5.52E-04, OR_GCA = 1.16). Taken together, our results provide evidence of strong genetic differences between GCA and TAK in the HLA. Outside this region, common susceptibility factors were suggested, especially within the IL12B locus.

Immune mechanisms in medium and large-vessel vasculitis

Vasculitis of the medium and large arteries, most often presenting as giant cell arteritis (GCA), is an infrequent, but potentially fatal, type of immune-mediated vascular disease. The site of the aberrant immune reaction, the mural layers of the artery, is strictly defined by vascular dendritic cells, endothelial cells, vascular smooth muscle cells and fibroblasts, which engage in an interaction with T cells and macrophages to, ultimately, cause luminal stenosis or aneurysmal wall damage of the vessel. A multitude of effector cytokines, all known as critical mediators in host-protective immunity, have been identified in vasculitic lesions. Two dominant cytokine clusters--the IL-6-IL-17 axis and the IL-12-IFN-γ axis--have been linked to disease activity. These two clusters seem to serve different roles in the vasculitic process. The IL-6-IL-17 cluster is highly responsive to standard corticosteroid therapy, whereas the IL-12-IFN-γ cluster is resistant to steroid-mediated immunosuppression. The information exchange between vascular and immune cells and stabilization of the vasculitic process involves members of the Notch receptor and ligand family. Focusing on elements in the tissue context of GCA, instead of broadly suppressing host immunity, might enable a more tailored therapeutic approach that avoids unwanted adverse effects of aggressive immunosuppression.

Pathology of Takayasu arteritis: A brief review

Takayasu arteritis (TA) is a chronic idiopathic and granulomatous vasculitis, manifesting mainly as a panaortitis. Autoimmune cell-mediated immunity is probably responsible for the disease. The inflammation commences from the adventitia and progresses to the intima and leads to, both in adults and children, segmental stenosis, occlusion, dilatation, and/or aneurysm formation. This review focuses briefly on the etiopathogenesis, and describes the pathological and clinical features in adults and children.