The pathogenesis of giant cell arteritis: morphological aspects.

Area of Science:

• Vascular pathology
• Immunohistochemistry
• Histopathology

Background:

• Giant cell arteritis (GCA) is an inflammatory condition affecting arteries.
• The pathogenesis of GCA, particularly the role of arterial changes, requires further elucidation.

Purpose of the Study:

• To investigate the light-microscopic, electron-microscopic, and immunocytochemical features of temporal arteries in GCA.
• To elucidate the cellular mechanisms and sequence of events in the inflammatory process of GCA.

Main Methods:

• Analysis of temporal artery biopsies using light microscopy, electron microscopy, and immunocytochemistry.
• Correlation of histological findings with arterial structural changes.

Main Results:

• Arterial atrophy and internal elastic membrane calcification appear to be prerequisites for GCA initiation.
• Foreign body giant cells form near calcifications, potentially derived from modified smooth muscle cells, and attack calcifications.
• A diffuse mononuclear cell infiltrate, leading to arterial dilation, is more common than focal reactions around calcifications.
• Langhans giant cells arise from macrophages in the diffuse infiltrate.

Conclusions:

• The inflammatory process in GCA may initiate as a focal foreign body giant cell reaction to arterial calcifications.
• This focal reaction potentially triggers a subsequent diffuse inflammation, leading to significant arterial dilation.