Pathogenesis of Radiation Sickness

Mechanisms of radiation damage to the salivary glands

Damage to the salivary glands by ionizing radiation is classified as traumatic and iatrogenic injury. The primary etiological cause is targeted radiation therapy for malignant neoplasms localized in the head and neck region.

The development of the pathological process (pathogenesis) is staged and includes two main phases:

1. Acute stage: An acute inflammatory reaction is immediately triggered in the affected glands in response to radiation-induced cell damage.
2. Chronic stage (outcome): The inflammatory process predictably transforms into chronic sclerosing sialadenitis, accompanied by the replacement of functional tissue with scar tissue.

Tissue sensitivity: It is important to note that not all structures react equally to ionizing radiation. Specifically, the serous acini of the parotid gland possess the highest susceptibility and sensitivity to irradiation.

Pathogenesis of radiation (aseptic) pericarditis

Radiation exposure to the chest area (e.g., during cancer treatment) can provoke the development of aseptic pericarditis. Unlike infectious forms, where the pathogen enters via hematogenous, lymphogenous, or contact routes, inflammation here develops without the direct participation of an infectious agent in the pericardial cavity.

Mechanism of damage:

• The key link in the pathogenesis is increased vascular wall permeability of the pericardium.
• The direct trigger initiating this process is the physical impact of radiation (along with possible systemic immunopathological reactions).

Phases of exudation in radiation pericarditis

The development of radiation-induced aseptic inflammation has a distinct morphological staging, which ultimately determines the clinical presentation and classification of the process:

• Initial phase: There is an increase in fluid effusion (exudation) from the blood vessels of the visceral layer (epicardium). The process begins in the area of large major vessels at the base of the heart, after which the fluid flows down the posterior wall.
• Formation of dry (fibrinous) pericarditis: If the volume of inflammatory exudate is small, the liquid fraction is reabsorbed fairly quickly. As a result, only fibrin strands remain on the surface of the pericardial layers.
• Formation of effusion (exudative) pericarditis: With high-intensity radiation injury and involvement of both the visceral and parietal layers, the volume of exudate increases sharply, and the tissues' ability to reabsorb it decreases. Fluid initially accumulates in the lower parts, mechanically displacing the heart forward and upward. With further progression, the exudate can fill the entire pericardial cavity.

The exudative process may stop at any of the described stages spontaneously or with treatment. Despite the severity of the damaging factor, the disease most often has a benign course and ends in recovery.

Class and exam questions

What else to study on this topic

• Pathomorphological picture of cytomegalovirus parotitis ("owl-eye" cells)
• Infectious pericarditis: routes of pathogen entry
• Obstructive disorders of the salivary glands (sialolithiasis, mucocele, retention cysts)
• Toxic-metabolic causes of aseptic pericarditis (uremia, gout)
• Systemic immunopathological reactions as triggers of polyserositis

Prepared by WhiteCoat Pro faculty in accordance with the medical school curriculum. For educational purposes only.