Ricin

Aka: Ricin, Ricin Poisoning, Ricinus Lectin, Castor Bean Lectin

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II. Pathophysiology

  1. Background
    1. Derived from seeds of the castor plant (Ricinus communis)
      1. Although originally native to Africa, castor plant now grows worldwide
    2. Ricin is a phytotoxin, Protein toxin used historically as Biological Weapon
      1. Used in assassination of Bulgarian exile Georgi Markov
        1. Gun disguised as Umbrella London 1978
        2. Implanted ricin pellet in his body
  2. Pharmacokinetics
    1. Heat resistant (<80 C, <176 F)
    2. Water soluble
    3. Tasteless
    4. Not removed with Hemodialysis
  3. Toxicity
    1. Highly cytotoxic
    2. Ricin B Chain binds specific complex Carbohydrates on cell surface
    3. Ricin complex is transported intracelleularly where it is taken up by the endoplasmic reticulum
    4. Ricin A chain activates and disrupts ribosomes, stopping Protein synthesis and resulting in cell death
  4. Exposures
    1. Ingestion
      1. Ingestion is most common source of Ricin Poisoning (other exposures are more difficult)
      2. Single ingested seeds are typically nontoxic unless chewed or crushed
    2. Small particle aerosol inhalation
      1. No secondary aerosol risk to healthcare workers
    3. Injection

III. Symptoms

  1. Early after Ingestion (first 6 hours): Gastrointestinal Symptoms
    1. Nausea, Voming or Diarrhea
    2. Ingestion of 4 to 8 beans (<=20 mg/kg ricin)
    3. Most severe or lethal if chewed or crushed
  2. Delayed ingestion effects (2 to 5 days after ingestion)
    1. Hepatotoxicity
    2. Nephrotoxicity
    3. Other systemic effects
      1. Tachycardia
      2. Hypotension
  3. After Inhalation (18-24 hours): Respiratory effects
    1. Severe respiratory distress and failure in 36-72 hours
    2. Cough
    3. Dyspnea
    4. Chest tightness
  4. Other Findings
    1. Weakness
    2. Fever
    3. Arthralgia

IV. Signs

  1. Pulmonary Edema
  2. Hypotension
  3. Vascular collapse
  4. Shock
  5. Disseminated Intravascular Coagulation (DIC)
  6. Multiple organ failure

V. Imaging: Inhalation

  1. Chest XRay
    1. Bilateral infiltrates on Chest Radiographs
    2. Pulmonary Edema

VI. Labs

  1. See Unknown Ingestion
  2. Complete Blood Count
    1. Neutrophilic Leukocytosis
  3. Comprehensive metabolic panel

VII. Differential Diagnosis

  1. Staphylococcal Enterotoxin B (SEB)
  2. Q Fever
  3. Tularemia
  4. Plague
  5. Phosgene (Chemical Toxin)

VIII. Course

  1. Pathologic changes seen as early as 8 hours after exposure

IX. Management

  1. See Unknown Ingestion
  2. Skin Decontamination
  3. Gastric Decontamination for ingestion
    1. Activated Charcoal if <1 hour after ingestion
    2. Consider Whole Bowel Irrigation (Polyethylene Glycol) for large ingestion
  4. Supportive care
    1. Intravenous Fluids
    2. Norepinephrine for refractory Hypotension
    3. Treat Pulmonary Edema
  5. Disposition
    1. May discharge if asymptomatic at 6 hours after exposure (esp. ingestion)

X. Prevention

  1. No Vaccine or antitoxin available

XI. References

  1. Tomaszewski (2024) Crit Dec Emerg Med 38(6): 38

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