Amanita Poisoning

Amanita phalloides (deathcap) is the most toxic amatoxin-containing mushroom species with an amatoxin content of about 2-3 mg/g dry tissue. Consequently, 1-3 fresh mushrooms probably contain lethal quantities of amatoxins. Alpha-amanitin is a cyclic octapeptide with a thioether bridge between the cystine and tryptophan. It inhibits RNA polymerase II), beta-amanitin (inhibits eukaryotic RNA polymerase II and III (but not RNA polymerase I or bacterial RNA polymerase) and mammalian protein synthesis. Both alpha-amanitin and gamma-amanitin produce the following toxic metabolites:

• Ibotenic Acid (a neurotoxic isoxazole; causes motor depression, ataxia, and changes in mood, perceptions and feelings, and is a potent excitatory amino acid agonist)
• Muscimol (neurotoxic isoxazole; a potent agonist at GABA-A receptors)

Amatoxins are stable compounds that do not degrade during cooking or drying and resist freezing.

The onset of GI symptoms usually ranges from 6-24 hours. Amatoxin poisoning has the following three stages after the onset of GI symptoms: 1) gastrointestinal phase; 2) latent period required for the amatoxins to bind to intranuclear RNA polymerase II and disrupt protein synthesis, and 3) hepatorenal phase.

The initial features of toxicity include a profuse, watery diarrhea, severe abdominal pain, nausea, vomiting, and sometimes bloody diarrhea. This phase usually lasts 12-36 hours. Fever, hyperglycemia, hypoglycemia, dehydration, and electrolyte imbalance may develop.

With adequate fluid and electrolyte replacement a remission of symptoms occurs, followed by the hepatorenal phase.

Within 3-4 days after the ingestion hepatic failure becomes obvious with jaundice, bleeding, hypoglycemia, delirium, confusion, and coma. Renal failure accompanies liver failure in most fatal cases. Poisoning may require liver transplantation.