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esponse. Precursor/stem cells are more sensitive than fully developed, mature cells.
Similarly, cells that are actively replicating (going through mitosis) are also more
responsive.
After receiving a radiation dose, a progressive, chronic, and complex inflammatory
process begins. The clinical course is a function of the following:
• Type of radiation.
• Inherent energy of the source.
• Dose and the dose rate.
• Length of exposure.
• Tissue involved.
• How the energy is distributed within that tissue.
• Size and area of the body involved in the exposure.
Although only a small superficial area may initially appear to be affected, because of the
amount of energy involved, deeper tissues and organ systems may also be affected.
Depending on the individual cells involved, onset of clinical symptoms will be variable.
Perhaps the most pertinent rule of thumb in these types of injuries is that there is no
pathognomonic sign or symptom of radiation injury. There is not always a specific linear
relationship between the dose of radiation that a tissue receives and the subsequent
somatic manifestations that result. Skin damage evolves over time according to the local
dose with the tissue furthest from the direct local injury being the slowest to display
damage. The extent of tissue damage or involvement is inversely proportional to the
square of the distance from the source of radiation. There is no definite correlation
between specific symptoms and cell types.
CRS has been divided into five time-related stages: prodromal erythematous,
manifestational, subacute, chronic, and late.
Prodromal erythematous stage. This stage may last minutes to hours after exposure to
doses >5–6 Gy. The time to onset, intensity, and duration are used to predict prognosis.
The early erythema is likely due to release of vasoactive amines and secondary
vasodilation. A clinically asymptomatic latent period may follow. At this stage, high-dose
and low-dose casualties cannot be distinguished. If additional symptoms (e.g., nausea,
vomiting, CNS changes) develop along with relevant patient history, then further
assumptions or conclusions will be possible.
Manifestational stage. After a latency period of 7–21 days, clinical signs develop that
range from bright erythemas with a burning sensation to painful blisters and ulcers. These
changes are due to injury to blood vessels and underlying connective tissue and death of
skin stem cells. From 8 to 12 Gy, there is dry desquamation, and from 15 to 20 Gy, moist
desquamation ensues. Moist desquamation occurs less commonly in children undergoing
radiation therapy than in adults. This is probably because of the ability of the epithelium
to recover more quickly in children than in adults. More changes are also observed in
fair-skinned individuals and at the more radiosensitive areas of the body such as the
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