Mushroom Poisoning

Mushroom poisoning results from ingestion of wild fungi that contain toxins, most often by foraging errors, and is seasonal (late summer and autumn in temperate regions). The key point is the time between eating and the first symptoms, which separates mostly benign early-onset syndromes (under 6 hours) from dangerous late-onset syndromes (over 6 hours).

Principal syndromes

• Amatoxin (Amanita phalloides, Amanita virosa, Galerina and some Lepiota species): the cause of about 90% of fatal mushroom poisonings. Amatoxins inhibit RNA polymerase II and are concentrated by the liver through enterohepatic recirculation. A single cap (about 30 g) of death cap can be fatal. Without treatment, mortality is 10 to 30%.
• Orellanine (Cortinarius orellanus and C. rubellus): delayed acute kidney injury 2 to 20 days after ingestion.
• Gyromitrin (false morel, Gyromitra esculenta): metabolized to monomethylhydrazine, which depletes pyridoxal phosphate and causes seizures, hemolysis and hepatic injury.
• Muscarine (Clitocybe and Inocybe species): cholinergic syndrome within 15 to 30 minutes.
• Isoxazoles (Amanita muscaria, Amanita pantherina): ibotenic acid and muscimol cause confusion, ataxia and sedation.
• Psilocybin (Psilocybe species): hallucinations.
• Coprine (Coprinopsis atramentaria): a disulfiram-like reaction with alcohol.
• Gastrointestinal irritants: many species cause self-limiting vomiting and diarrhea.

Amatoxin poisoning evolves in three phases: a latent phase of 6 to 24 hours, a gastrointestinal phase of profuse vomiting and cholera-like diarrhea (6 to 24 hours), a false recovery at 24 to 48 hours, and then hepatic and renal failure at 48 to 96 hours. Complications: fulminant liver failure, hepatic encephalopathy, coagulopathy, acute kidney injury, cerebral edema and death.

• Early onset (under 6 hours): vomiting, diarrhea, sweating, salivation, lacrimation, bradycardia, miosis (muscarinic), confusion, delirium, ataxia, hallucinations
• Late onset (6 to 24 hours): severe vomiting, watery or bloody diarrhea, abdominal cramps and dehydration (amatoxin), then jaundice, bleeding, confusion and coma from liver failure
• Orellanine: flank pain, nausea, thirst, polyuria then oliguria, 2 to 20 days after ingestion
• Gyromitrin: vomiting, headache, seizures, jaundice and hemolysis within 6 to 12 hours
• Red flags: symptoms starting after 6 hours, a mixed meal of several species, persistent vomiting with diarrhea, rising liver enzymes, and a group poisoned from the same meal

1. History: time of the meal, number of people affected, species picked, preparation, and any left-over mushrooms. Keep any specimens, vomitus and photographs for identification by a mycologist.
2. Laboratory tests: liver tests (AST and ALT rise at 24 to 48 hours), INR, glucose, creatinine, urea, electrolytes, lactate, bilirubin, full blood count and creatine kinase. Repeat liver tests and INR every 6 to 12 hours for at least 72 hours in suspected amatoxin ingestion.
3. Urine amatoxin assay (immunoassay, detects within 36 to 48 hours of ingestion) and spore microscopy of stomach contents or specimens.
4. ECG and monitoring for bradycardia and arrhythmia in muscarinic poisoning.
5. Liver ultrasound, and CT head if encephalopathy develops.

Differentials: viral gastroenteritis, food poisoning from bacteria or toxins, acute viral hepatitis, paracetamol poisoning, cholera, other plant poisoning.

1. Fluids and electrolytes: aggressive IV crystalloid 20 mL/kg and repeat (losses can exceed 10 litres in a day), with potassium, magnesium, glucose and acid-base correction. Antiemetic: ondansetron 4 to 8 mg IV (children 0.15 mg/kg).
2. Gut decontamination: activated charcoal 50 g orally (children 1 g/kg, maximum 50 g) within a few hours, and repeated 25 to 50 g every 4 hours for the first 24 to 48 hours in amatoxin poisoning if the gut is working (interrupting enterohepatic circulation).
3. Amatoxin poisoning (start on suspicion, without waiting for results):
   • Silibinin (a milk thistle extract) 5 mg/kg IV over 1 hour, then 20 mg/kg a day as a continuous infusion for 3 days or until recovery.
   • N-acetylcysteine 150 mg/kg IV over 1 hour, then 50 mg/kg over 4 hours, then 100 mg/kg over 16 hours (a total of 300 mg/kg over 21 hours), continued at 6.25 mg/kg/h in liver failure.
   • Benzylpenicillin in high doses has been used (300,000 to 1,000,000 units/kg a day IV), but with uncertain benefit.
   • Monitoring in a high-dependency setting with early transfer to a liver transplant centre.
4. Indications for liver transplantation: INR over 2.0 at 48 hours, or over 6.0 at any time, rising bilirubin over 100 micromol/L, falling factor V, hepatic encephalopathy, or acute kidney injury. Haemodialysis and molecular adsorbent recirculating system (liver support) as a bridge.
5. Muscarine poisoning: atropine 0.5 to 1 mg IV every 5 to 10 minutes titrated to dry bronchial secretions and heart rate over 80 beats a minute (children 0.02 mg/kg, minimum 0.1 mg).
6. Isoxazole and psilocybin poisoning: a quiet environment, and benzodiazepines (diazepam 5 to 10 mg IV or lorazepam 1 to 2 mg IV) for agitation and hallucinations. Avoid physostigmine and atropine.
7. Gyromitrin poisoning: pyridoxine 25 mg/kg IV over 15 to 30 minutes (maximum 25 g in a day) for seizures, with benzodiazepines, and methylene blue 1 to 2 mg/kg IV for methemoglobinemia.
8. Orellanine poisoning: supportive care and haemodialysis for kidney failure. Charcoal haemoperfusion has been used early. Kidney function may take months to recover and some patients need transplantation.
9. Coprine reaction: supportive care and avoidance of alcohol for 3 to 5 days.
10. Seizures: lorazepam 4 mg IV (children 0.1 mg/kg, maximum 4 mg).

Observation: at least 24 hours for suspected amatoxin, or 48 to 72 hours if the species is unknown, even in asymptomatic patients who ate a risk species. All people who ate the same meal must be assessed. Follow-up includes liver and renal function until normal. Counsel never to eat wild mushrooms unless identified by an expert, not to rely on folk rules (peeling, cooking or color), and that cooking and freezing do not destroy amatoxins.