Origin of disease
The inflammatory destruction of the vessels occurs in two different ways, for which the own immune system is responsible: On the one hand, defence cells (white blood cells, large leukocytes) form proteins (so-called antibodies), which attach themselves to the structures of the vessels and subsequently start a chain reaction in which various endogenous cells as well as enzymes and messenger substances (mediators) that destroy the vessels are involved (so-called immune reaction type II). The inflammation typically involves so-called giant cells (hence the name), which can be detected in the microscopic examination of affected vessels (see below). The second possibility of vascular damage is the undesired connection of the proteins formed by overreacting immune cells with the body’s own structures (antigens) floating in the blood.
These compounds are called immune complexes and also initiate the destructive chain reaction. In both cases, the result is damage to the blood vessels. In addition, the elastic membrane between the two layers of the vessel wall breaks down into pieces.
These characteristic vascular changes make it easier to clearly identify (if the clinical symptoms are not sufficient) giant cell arteritis (Horton’s disease) when viewing tissue samples under the microscope. However, clear detection of existing vascular changes is easier than the reliable exclusion of a disease, since the entire vessel need not be affected.Then the material of the tissue sample is apparently healthy and inconspicuous, because a non-infected area of the vessel was taken by chance (so-called skip lesions). To avoid this, pieces of vessel more than two centimeters long are often removed.
An ultrasound examination (sonography) can also provide the first indications of giant cell arteritis (Horton’s disease) with narrowing of the vessels. An ultrasound examination can determine the thickness of the vessels. Especially in the case of large vessels, the thickness of the vessel wall can be determined down to the millimeter.
A concealed vessel wall in the ultrasound examination can indicate Horton’s disease. However, other vascular diseases, such as arteriosclerosis, can also cause a thickening of the vessel wall.
- Inner (called intima) vascular layers and
- The middle layer, consisting of small, specialized muscle cells (media).
