Radiation Syndrome: Understanding Acute and Chronic Radiation Effects
1. Dr. Samatbek Turdaliev
2. Mayavan Swetha
Kuntal Arzu
Shaik Manusha
(1. Lecturer, Dept. Of Hospital Therapy, International Medical Faculty, Osh State University, Osh, Kyrgyz Republic.
2. Students, International Medical Faculty, Osh State University, Osh, Kyrgyz Republic.)
OVERVIEW
Radiation syndrome refers to the spectrum of clinical effects caused by exposure to ionizing radiation. It includes both acute radiation syndrome (ARS), resulting from a high dose exposure over a short time, and chronic radiation syndrome from prolonged or repeated lower doses. Understanding the pathophysiology, clinical manifestations, investigations, and management of these syndromes is critical for preparedness in nuclear accidents, radiation therapy mishaps, and occupational exposures. This article presents a comprehensive and detailed exploration of radiation syndrome, emphasizing its acute and chronic effects.
ABSTRACT
Radiation syndrome arises from exposure to ionizing radiation and manifests as acute or chronic health effects depending on dose and duration. Acute radiation syndrome is characterized by a rapid onset of symptoms affecting hematopoietic, gastrointestinal, and neurovascular systems following high-dose exposure. Chronic radiation syndrome results from long-term low-dose exposure leading to cumulative tissue damage and increased cancer risk. This article reviews the causes, pathology, clinical features, diagnostic strategies, and therapeutic approaches to radiation syndrome, underscoring the importance of early recognition and multidisciplinary management to improve prognosis.
Keywords: Radiation syndrome, acute radiation syndrome, chronic radiation syndrome, ionizing radiation, hematopoietic syndrome, gastrointestinal syndrome, neurovascular syndrome, radiation toxicity, radiation exposure management
Introduction
Radiation syndrome is a clinical condition caused by exposure to ionizing radiation—high-energy particles or waves capable of ionizing atoms and molecules. Ionizing radiation damages DNA and cellular structures, predominantly affecting rapidly dividing cells such as bone marrow, gastrointestinal tract epithelium, and hair follicles. The syndrome is classified into acute and chronic forms based on exposure characteristics. ARS occurs with whole-body or significant partial-body dose exceeding 0.7 Gray (Gy) delivered within minutes to hours, often in nuclear accidents or radiological emergencies. Chronic radiation syndrome develops gradually from cumulative lower doses over months to years, leading to systemic effects including fibrosis, organ dysfunction, and carcinogenesis. Recognition of clinical patterns and timely investigation are essential for appropriate intervention.
CAUSES AND TYPES
CAUSES
The main cause of radiation syndrome is exposure to ionizing radiation from various sources including:
- Nuclear power plant accidents (e.g., Chernobyl, Fukushima)
- Atomic bomb detonations
- Accidents involving medical radiation devices or radiotherapy overdoses
- Occupational exposures in nuclear industry or radiology without adequate protection
- Ingestion or inhalation of radioactive materials contaminating food, air, or water
- Radiological terrorism such as “dirty bombs”
Exposure can be external, involving whole or partial body irradiation, or internal through contaminated radioactive particles inside the body affecting tissues over time.
TYPES
Radiation syndrome is divided primarily into:
1. ACUTE RADIATION SYNDROME (ARS) Occurs after exposure to a large radiation dose (≥0.7 Gy) over a short time. It is characterized by three classic sub-syndromes depending on dose and organ system affected:
i. Hematopoietic Syndrome (2-10 Gy): The most common form, resulting from bone marrow damage causing reductions in white blood cells, red blood cells, and platelets. Patients are prone to infections, anemia, and bleeding. Symptoms appear days to weeks after exposure.
ii. Gastrointestinal Syndrome (6-20 Gy): Caused by destruction of intestinal crypt cells leading to nausea, vomiting, diarrhea, dehydration, and sepsis. Death occurs within 3-10 days without intensive care.
iii. Neurovascular (Cerebrovascular) Syndrome (≥20 Gy): The most severe, affecting the brain and nervous system. Symptoms such as headache, confusion, ataxia appear within hours, progressing rapidly to coma and death within 48 hours.
The clinical course of ARS consists of prodromal symptoms (nausea, vomiting within hours), a latent phase, then manifest illness varying by syndrome severity. Doses above 8 Gy are usually fatal despite treatment.
Chronic Radiation Syndrome (CRS)
CRS results from repeated or prolonged low-dose exposure to radiation, causing progressive tissue damage. It manifests with skin atrophy, fibrosis, cataracts, chronic anemia, immunosuppression, and increased risk of cancers such as leukemia and solid tumors. Symptoms develop over months to years, often insidiously. CRS can also involve neurological deficits and chronic inflammatory states. Latent periods for radiation-induced cancer span 7 to 30 years.
INVESTIGATION
Clinical suspicion for radiation syndrome is based on exposure history and symptom onset. Investigations aim to evaluate severity and organ involvement:
1.Complete blood count (CBC): To detect leukopenia, thrombocytopenia, and anemia indicative of hematopoietic damage.
2.Cytogenetic tests: Dicentric chromosome assay and other biomarkers confirm radiation exposure and estimate dose.
3.Biochemical tests: Monitor electrolytes, renal and liver function, and inflammatory markers.
4.Physical examination: Skin inspection for burns, alopecia, mucosal ulcerations.
5. Imaging: Abdominal imaging/endoscopy for gastrointestinal injury, brain imaging if neurovascular syndrome suspected.
6. Dose assessment: Environmental and biological dosimetry to estimate exposure levels.
Repeated CBCs over 2-4 weeks track marrow recovery or failure. Early diagnosis assists in prognosis and treatment planning.
MANAGEMENT
Management of radiation syndrome is multidisciplinary and depends on syndrome type and severity:
General and supportive care
- Rapid decontamination by removing contaminated clothing and washing skin
- Fluid and electrolyte replacement to treat dehydration and maintain organ perfusion
- Nutritional support, including parenteral nutrition for gastrointestinal syndrome
- Pain control and wound care for radiation burns and mucositis
Specific treatment by syndrome
1.Hematopoietic syndrome:
Administration of hematopoietic growth factors (e.g., granulocyte colony-stimulating factor, G-CSF) to stimulate bone marrow recovery, blood transfusions for anemia and thrombocytopenia, and antibiotics to prevent/treat infection. Severe marrow failure may require bone marrow or stem cell transplantation.
2.Gastrointestinal syndrome:
Supportive care focusing on hydration and infection control; sometimes surgical intervention for bowel perforation or necrosis.
3.Neurovascular syndrome:
Largely supportive as treatment options are limited; prognosis is very poor.
Pharmacological interventions
- Potassium iodide to block radioactive iodine uptake by the thyroid in radioiodine exposure
- Chelating agents to remove internalized radionuclides
- Anti-nausea and anti-diarrheal medications
Long-term follow-up
Surveillance for delayed effects including secondary cancers, cataracts, and chronic organ dysfunction is critical. Psychosocial support for radiation victims is important due to the psychological impact of exposure and illness.
REFERENCES
1. López M, et al. Medical management of the acute radiation syndrome – PMC. 2011. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC3863169/
2. Acute Radiation Syndrome – Wikipedia. 2025. Available from: https://en.wikipedia.org/wiki/Acute_radiation_syndrome
3. Radiation Injury – MSD Manuals. 2025. Available from: https://www.msdmanuals.com/home/injuries-and-poisoning/radiation-injury/radiation-injury
4. CDC. Acute Radiation Syndrome: Information for Clinicians. 2024. Available from: https://www.cdc.gov/radiation-emergencies/hcp/clinical-guidance/ars.html
5. NRC. Early (Acute) Effects of Radiation. 2010. Available from: https://www.nrc.gov/docs/ml1122/ML11229A693.pdf
6. NCBI Bookshelf. Radiation Syndrome – StatPearls. 2023. Available from: https://www.ncbi.nlm.nih.gov/books/NBK441931/
This comprehensive review elucidates the clinical spectrum and pathophysiology of radiation syndrome, highlighting diagnostic criteria and therapeutic strategies necessary for effective management and mitigation of both acute and chronic radiation effects.
CITATIONS:
[1] Acute radiation syndrome https://en.wikipedia.org/wiki/Acute_radiation_syndrome
[2] Medical management of the acute radiation syndrome – PMC https://pmc.ncbi.nlm.nih.gov/articles/PMC3863169/
[3] Radiation Injury – Injuries and Poisoning https://www.msdmanuals.com/home/injuries-and-poisoning/radiation-injury/radiation-injury
[4] 16 – Early (Acute) Effects of Radiation. https://www.nrc.gov/docs/ml1122/ML11229A693.pdf
[5] Acute radiation syndrome and chronic radiation syndrome https://nuclmed.gr/wp-content/uploads/2017/03/60-1.pdf
[6] A Brochure for Physicians https://www.cdc.gov/radiation-emergencies/media/pdfs/ARS.pdf
[7] Acute Radiation Syndrome: Information for Clinicians https://www.cdc.gov/radiation-emergencies/hcp/clinical-guidance/ars.html
[8] Diagnosis and Treatment of Radiation Injuries https://www-pub.iaea.org/MTCD/Publications/PDF/P040_scr.pdf
[9] Radiation Health Effects | US EPA https://www.epa.gov/radiation/radiation-health-effects
[10] Radiation Syndrome – StatPearls – NCBI Bookshelf https://www.ncbi.nlm.nih.gov/books/NBK441931/