Aetiology

The aetiology of Takayasu's arteritis is unknown. Environmental and genetic factors are thought to play roles in the development of the disease.[4]​ Cell-mediated immune mechanisms have been implicated.[1] Genetic screening has shown polymorphisms in IL-12, IL-6, and IL-2 genes in a population of Turkish patients with Takayasu's arteritis.[15] HLA-Bw5 and HLA-B39.2 are reportedly increased in frequency in some populations.[16][17]

Pathophysiology

Takayasu's arteritis is an immune-mediated vasculitis characterised by granulomatous inflammation of large arteries. Cell-mediated immune mechanisms have been implicated.[1][4]​​​ Interleukin (IL)-6 and IL-17 are thought to play an important role in the pathogenesis of Takayasu's arteritis.[18]​ Some patients have been treated with an IL-6 inhibitor with favourable responses.[19][20]​

The immunological and inflammatory response seen in arteries is similar to that observed in large arteries in giant cell arteritis.[1][4]​​ During the acute phase of vasculitis, inflammation begins in the vasa vasora of the adventitia of muscular arteries.[1][9]​ T cells are prominent in the initial cellular response, and anti-endothelial cell antibodies may also be involved.[1][4][21][22]​​​[Figure caption and citation for the preceding image starts]: Photomicrograph of the aorta from a patient with Takayasu's arteritis demonstrates marked thickening of the intimal layer and inflammatory infiltrates in the media and laminar necrosisUsed with permission from the collection of Dylan Miller, MD, Mayo Clinic [Citation ends].com.bmj.content.model.Caption@4ca52d5b

Classification

2012 International Chapel Hill Consensus Conference on the Nomenclature of Vasculitides[5]

Categorises vasculitis based upon the predominant type of vessels involved, and other features including aetiology, pathogenesis, type of inflammation, favoured organ distribution, clinical manifestations, genetic predispositions, and distinctive demographic characteristics.

  • Large vessel vasculitis

    • Takayasu's arteritis

    • Giant cell arteritis

  • Medium vessel vasculitis

    • Polyarteritis nodosa

    • Kawasaki disease

  • Small vessel vasculitis

    • ANCA-associated vasculitis

    • Microscopic polyangiitis

    • Granulomatosis with polyangiitis (formerly known as Wegener's granulomatosis)

    • Eosinophilic granulomatosis with polyangiitis (Churg-Strauss)

    • Immune complex vasculitis

    • Anti-glomerular basement membrane (anti-GBM) disease

    • Cryoglobulinaemic vasculitis

    • IgA vasculitis (Henoch-Schönlein)

    • Hypocomplementaemic urticarial vasculitis

  • Variable vessel vasculitis

    • Behçet's disease

    • Cogan's syndrome

  • Single-organ vasculitis

  • Vasculitis associated with systemic disease

  • Vasculitis associated with probable aetiology

Angiographic classification of Takayasu's arteritis[6]

Classification is based on the vessels involved in the inflammatory process as seen on angiography.

  • Type I: Branches of the aortic arch

  • Type IIa: Ascending aorta, aortic arch, and branches of the aortic arch

  • Type IIb: Ascending aorta, aortic arch, and its branches and thoracic descending aorta

  • Type III: Thoracic descending aorta, abdominal aorta, and/or renal arteries

  • Type IV: Abdominal aorta and/or renal arteries

  • Type V: Features of types IIb and IV

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