Temporal arteritis pathophysiology

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Hamid Qazi, MD, BSc [2]

Overview

Temporal arteritis is caused by transmural inflammation of elastic arteries. It is understood that temporal arteritis is the result of cell mediated immunity which arises as a response to endothelial injury and is antigen-driven disease with T-cell and macrophage activation in the elastic tissue in the arterial walls. The adventitia of the vessel is the initial site of immunologic injury. The activation of dendritic cells in the adventitia causes a production of chemokines that recruit CD4+ T helper cells. The CD4+ T helper cell convert in to Th17 cells which produce interleukin 17 and Th1 cells which produce interferon gamma. Giant cell are one of many inflammatory cells that are recruited and produce growth factor which narrows and obstructs the vessels. The concentric inflammation occurs in segments. Macrophages in the adventia produce interleukin 6. While in the intima and media of the vessel, macrophages produce vascular endothelial growth factor (VEGF) and metalloproteinases which destroy the internal elastic lamina. An increased activated platelets express P-selectin which may cause vessel inflammation and thromboembolic events. Temporal arteritis arises from giant cells, which are fused monocytes cells that are normally involved in the body immune response. Because the disease involves only arteries with internal elastic lamina, the aortic arch and its branches are often involved. Intracranial arteries do not have internal elastic lamina and are not involved.

Pathophysiology

Pathogenesis

  • It is understood that temporal arteritis is the result of cell mediated immunity which arises as a response to endothelial injury and is an antigen-driven disease with local T-cell and macrophage activation in the elastic tissue of arterial walls with an important role of the proinflammatory cytokines.[21][29, 30]
  • The adventitia of the vessel is the initial site of immunologic injury. The activation of dendritic cells in the adventitia causes a production of chemokines that recruit CD4+ T helper cells. The CD4+ T helper cell convert in to Th17 cells which produce interleukin 17 and Th1 cells which produce interferon gamma.
  • Giant cell are one of many inflammatory cells that are recruited and produce growth factor which narrows and obstructs the vessels.[10][13]
  • The concentric inflammation occurs in segments.[11]
  • Macrophages in the adventia produce interleukin 6.[13] While in the intima and media of the vessel, macrophages produce vascular endothelial growth factor (VEGF) and metalloproteinases which destroy the internal elastic lamina.[12][13]
  • An increased activated platelets express P-selectin which may cause vessel inflammation and thromboembolic events. [16]
  • Temporal arteritis arises from giant cells, which are fused monocytes cells that are normally involved in the body immune response.
  • Because the disease involves only arteries with internal elastic lamina, the aortic arch and its branches are often involved. Intracranial arteries do not have internal elastic lamina and are not involved. The distribution of involved arteries are as follows:

Commonly involved sites: [3, 4][7]18]

  • External vertebral arteries: It is less common though for the disease to extend more than 5 mm beyond the dural penetration.

Less commonly involved sites:

Genetics

  • Temporal artertis has an association with the HLA-DR4 haplotype.[24]
  • An association between Toll-like receptor 4 gene polymorphism and biopsy-proven GCA has been found. [25]

Associated Conditions

Gross Pathology

  • On gross pathology, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].

Microscopic Pathology

  • On microscopic histopathological analysis, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].

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