Toxicity, Mushrooms

Background: Mushroom toxicity is a worldwide concern. The increased use of mushrooms as components of organic diets, for alternative therapies, and by unsupervised children accounts, in part, for the renewed interest in mycetism. While most mushroom ingestions do not cause a clinically significant toxidrome, the lethal potential of a select few make mushroom toxicity an important subject. The incidence of mushroom poisoning in the US peaks in accordance with regional mushroom growing seasons, and case frequency has increased on the West Coast. Ingestion is the most common route of entry, but intravenous injection of mushroom toxins and inhalation of mushroom spores have been reported.

Mushroom toxidromes may be classified according to toxin and clinical presentation. Mushroom toxins have been divided into the following 7 main categories:
Amatoxins (cyclopeptides)

Orellanus (Cortinarius species)

Gyromitrin (monomethylhydrazine)

Muscarine

Ibotenic acid

Psilocybin

Coprine (disulfiramlike)
Some authors have created an eighth category comprising a vast range of species that only cause gastrointestinal symptoms.

Amanitin phalloides syndrome or Mycetismus choleriformis accounts for 90-95% of all fatalities from mushroom poisoning in North America. This discussion follows a clinical format because the offending mushroom is frequently unavailable for identification and poisoning may occur from a single species or a combination of different species. Trestrail’s data indicate that the mushroom was available for identification in only 3.4% of exposures.

Query patients presenting to the emergency department with compatible clinical scenarios about mushroom ingestion. Even a small piece of a toxic mushroom may cause death. Cooking, salting, or drying does not inactivate all mushroom toxins, and cooking fumes from certain species can cause poisoning.
Pathophysiology: Each mushroom group exerts its toxic effect by a different mechanism, and certain toxins have a predilection for individual organ systems. The amatoxins (cyclic octapeptides), which include amanitin, verotoxin, and phalloides, cause severe hepatocellular damage by inhibiting RNA polymerase II, thereby inhibiting protein synthesis at the cellular level, causing cell death. Other organ systems with high turnover rates (eg, gastrointestinal tract, kidneys) also are affected severely. Ibotenic acid and muscimol bind to glutamic acid and GABA receptors, respectively, and thereby interfere with CNS receptors. Monomethylhydrazine (MMH) from gyromitrin-containing mushrooms affects the GI tract, liver, and kidneys by inhibiting pyridoxine-dependent pathways in the synthesis of GABA. Muscarine affects the autonomic nervous system. It acts through depolarization of muscarinic acetylcholine receptors and exerts a peripheral cholinergic effect through stimulation of the postganglionic parasympathetic receptors. Coprine
inhibits aldehyde dehydrogenase, producing a disulfiramlike reaction in those consuming ethyl alcohol. Psilocybin indole exerts its effect on the central nervous system by stimulation of serotonin receptors. Orellanine and orelline, the bipyridyl toxins isolated from Cortinarius orellanus, exhibit their nephrotoxic effects by inhibiting alkaline phosphatase of the proximal tubule cells. Genetic factors may contribute to the clinical manifestations of this toxin, which has toxicity that is not reduced by cooking or drying.
Frequency:
In the US: Incidence of mushroom toxicity is reported to be 5 exposures per 100,000 population per year. According to a 12-year study by Goldfrank et al, more than 50% of patients experienced no symptoms, 25% were treated in a health care facility, 10-15% had minor symptoms, less than 5% had moderate symptoms, and 0.2% suffered major toxicity. In 1999, the American Association of Poison Control Centers reported 8996 mushroom exposures with 2930 treated in a health care facility and 6 fatalities.
Mortality/Morbidity: Mortality rate is estimated at 0.016%.

Race: No scientific data have found that outcomes of mushroom toxicity are dependent on race.

Sex: No scientific data have found that outcomes of mushroom toxicity are dependent on sex.

Age: According to the Toxic Exposure Surveillance System of the American Association of Poison Control Centers’ 1999 report, 5976 mushroom ingestions were reported in those younger than 6 years.