Emily Johnson
Mushrooms are widely consumed and used for their nutritional and medicinal properties. However, some species contain toxic substances that can lead to mushroom poisoning, which can range from mild gastrointestinal discomfort to organ failure and death. The most common cause of mushroom poisoning is the misidentification of toxic mushrooms as edible species, often due to their similar appearance. While boiling, cooking, freezing, or processing may reduce toxicity in some mushrooms, it does not always eliminate it. Therefore, it is crucial to correctly identify mushroom species before consumption to prevent poisoning.
| Characteristics | Values |
|---|---|
| Number of toxic mushroom species | 100 out of 14,000 |
| Number of ingestions in the US | 6,000 per year |
| Proportion of ingestions by children under six | Over 50% |
| Common symptoms | Gastrointestinal upset, abdominal cramping, nausea, vomiting, diarrhoea |
| Less common symptoms | Chest pain, seizures, intestinal fibrosis, erythromelalgia, rhabdomyolysis |
| Serious symptoms | Liver failure, kidney failure, neurologic sequelae, organ failure, death |
| Toxins | Amatoxins, Orellanine, Muscarine, Cyclopeptides, Coprine, Illudins |
| Toxin effects | Inhibition of RNA polymerase II, disruption of protein synthesis, stimulation of muscarinic receptors, altered sensorium, euphoria, cholinergic toxicity, disulfiram-like reaction |
| Toxic mushrooms | Omphalotus spp., Jack-o-lantern mushrooms, Clitocybe dealbata, Verpa bohemica, Galerina marginata, Amanita, Lepiota, Galerina, Cortinarius, Psilocybe, Inocybe |
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What You'll Learn
- Amatoxins, the most common cause of mushroom-related fatalities in the US
- Orellanine, a toxin that causes kidney failure
- Muscarine, a toxin that stimulates the nerves and muscles
- Cyclopeptides, a family of toxins with varying levels of toxicity
- Misidentification, the most common cause of mushroom poisoning
Amatoxins, the most common cause of mushroom-related fatalities in the US
Amatoxins are a group of at least nine cyclic peptide toxins found in three genera of poisonous mushrooms: Amanita, Galerina, and Lepiota. They are the most common cause of mushroom-related fatalities in the US, responsible for more than 95% of deaths. Amatoxins are potent inhibitors of RNA polymerase II, a vital enzyme in the synthesis of messenger RNA (mRNA). Without mRNA, which serves as the template for protein synthesis, cell metabolism stops, leading to cell death and apoptosis.
The toxins act rapidly, with gastrointestinal effects typically occurring 6-12 hours post-ingestion, followed by a quiescent period of 24-36 hours with symptomatic improvement. However, during this seemingly calm phase, amatoxins are causing insidious damage to the liver, leading to fulminant liver failure within 48 hours. This damage is characterised by the disintegration of nucleoli and pathologically centrilobular hepatic necrosis. Late onset of vomiting and watery diarrhoea may occur due to the presence of phallotoxins, another toxin found in amatoxin-containing mushrooms.
The severity of symptoms and the progression to liver failure depend on the amount of toxin ingested. Amatoxins are so potent that even half a mushroom cap can cause severe liver injury. The highest concentrations of amatoxins are found in the gills and cap of the mushroom, with lower levels in the spores and mycelium.
While amatoxin poisoning is rare, it is a significant concern due to its high fatality rate. The best course of action, if suspected, is to seek immediate medical attention. Prompt emesis within the first two hours of ingestion, coupled with early and aggressive hospital treatment, significantly improves the chances of survival and full recovery.
To prevent amatoxin poisoning, it is crucial to properly identify mushrooms before consumption. Amatoxin-containing mushrooms often closely resemble edible species in colour and morphology, leading to accidental ingestion. Foragers and mushroom hunters should familiarise themselves with both edible and toxic mushroom species to minimise the risk of poisoning.
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Orellanine, a toxin that causes kidney failure
Orellanine is a toxin found in certain mushrooms, notably those from the Cortinarius genus, such as the fools webcap (Cortinarius orellanus). It was first isolated in 1962 by Stanisław Grzymala, who identified its nephrotoxicity, or ability to cause kidney injury.
Orellanine is unique among mushroom toxins in that it specifically targets the kidneys, leading to acute kidney injury (AKI) in humans. Its mechanism of toxicity is not yet fully understood, but it is believed to inhibit the synthesis of essential biomolecules such as proteins, RNA, and DNA. Orellanine is also resistant to conventional cooking and storage methods like boiling, freezing, and drying, so it can remain toxic even when exposed to these conditions.
The effects of orellanine poisoning may not be apparent for 3 to 20 days after ingestion, with kidney failure typically beginning around day 11 and becoming symptomatic by day 20. Symptoms can include pain in the kidney area, thirst, vomiting, headache, and fatigue. In a mass poisoning incident in Poland in the 1950s, 24 out of 102 individuals who ingested the toxin developed AKI, and 10 of them died, likely due to the unavailability of hemodialysis or kidney transplants at the time.
Orellanine poisoning can be challenging to diagnose due to the delayed onset of symptoms, and it may not be detected in standard clinical samples collected within the first two days or even as late as 18 days post-ingestion. However, early symptoms may be present due to the presence of other toxins in the mushrooms.
Interestingly, despite its toxicity, orellanine has shown potential as a future cancer treatment. Its ability to selectively target proximal tubular cells has led to promising preclinical results in treating metastatic clear cell renal cell carcinoma.
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Muscarine, a toxin that stimulates the nerves and muscles
Mushrooms are the fruiting bodies of a group of higher fungi that have evolved contemporaneously with plants for millions of years. They are widely distributed throughout the world. While there are thousands of mushroom species, only about 100 are toxic and cause the majority of poisoning cases in humans.
One such toxin is muscarine, a natural product found in certain mushrooms, particularly in Inocybe and Clitocybe species. It is also found in the genera Entoloma, Mycena, Boletus, Hygrocybe, Lactarius, and Russula. The concentration of muscarine varies across these genera, with Inocybe and Clitocybe containing the highest concentrations of up to 1.6%.
Muscarine stimulates the muscarinic receptors of the nerves and muscles. It mimics the function of acetylcholine, a natural neurotransmitter in the cholinergic nervous system. This stimulation can lead to a range of symptoms, including sweating, salivation, tears, blurred vision, palpitations, and, in high doses, respiratory failure.
The severity of symptoms depends on the concentration of muscarine ingested. In severe poisoning cases, muscarine can cause cardiovascular collapse and even death. However, it is important to note that muscarine is contraindicated in individuals with certain conditions, such as asthma, COPD, or peptic ulcer disease, as it may have adverse effects.
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Cyclopeptides, a family of toxins with varying levels of toxicity
Cyclopeptides are a family of toxins with varying levels of toxicity. They are found in mushrooms of the genus Amanita, Galerina, and Lepiota, and are responsible for a significant number of mushroom poisoning cases. These toxins can lead to severe health issues, including gastroenteric sickness, hepatic failure, and renal damage.
Cyclopeptides include amatoxins, phallotoxins, and virotoxins. Amatoxins are considered highly toxic and are synthesized by some species of Amanita, Galerina, and Lepiota. They are cyclic octapeptides that contain eight amino acids. Phallotoxins, on the other hand, have medium toxicity and include seven residue peptides. Virotoxins are not toxic.
Amatoxins are the most common cause of mushroom-related fatalities, responsible for over 90% of deaths from macrofungi ingestion in the Western world. They inhibit RNA polymerase II and protein synthesis, leading to hepatocellular damage. Alpha-amatoxin, a subtype of amatoxin, is rapidly absorbed by the gastrointestinal tract and may cause acute liver failure. Other subtypes of amatoxins include beta-amanitin and gamma-amanitin.
Mushroom poisoning due to cyclopeptide toxins can be challenging to diagnose. It often involves obtaining a history of ingestion and analyzing suggestive physical findings, such as acute gastroenteritis or toxic hepatitis. Advanced analytical techniques, such as ultra-high-performance liquid chromatography coupled with mass spectrometry, play a crucial role in detecting cyclopeptide toxins and their analogues in mushroom samples.
The severity of cyclopeptide mushroom poisoning can vary depending on various factors, including the amount of toxin ingested, individual susceptibility, and the presence of other toxins or confounding factors. While children are frequently exposed to nontoxic mushrooms, older individuals are at a higher risk of developing severe complications from mushroom poisoning compared to healthy young adults.
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Misidentification, the most common cause of mushroom poisoning
Mushroom poisoning, or toxicity, occurs when someone ingests mushrooms that contain toxins. There are thousands of mushroom species, but only about 100 are toxic and cause the majority of poisoning cases. Of these, 15-20 species are potentially lethal when ingested. Poisoning can range from mild gastrointestinal discomfort to organ failure and death.
The most common cause of mushroom poisoning is misidentification. In over 95% of cases, poisoning occurs because an amateur forager misidentifies a toxic mushroom as an edible one. This is often due to a close resemblance in terms of colour and general morphology. For example, the toxic yellow-staining mushroom (Agaricus xanthodermus) is the most commonly eaten poisonous mushroom in Victoria, Australia, because it resembles edible mushrooms. It grows in lawns and gardens and can be identified by its white cap, which becomes brown with age, and its yellow-staining cap and stem. Another example is the Jack-o-lantern mushroom, which is sometimes mistaken for a chanterelle because both are bright orange and fruit at the same time of year. However, Jack-o-lantern mushrooms contain illudins, which cause gastrointestinal symptoms.
To avoid misidentification, foragers should familiarize themselves with the mushrooms they intend to collect, as well as with any similar-looking toxic species. They should also be aware that some mushrooms, such as those containing amatoxins, cannot be rendered safe to eat by cooking. It is recommended that only mushrooms bought from a reputable source, such as a supermarket or greengrocer, are consumed. If someone has eaten a poisonous mushroom, they should seek immediate medical attention.
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Frequently asked questions
Mushrooms contain a variety of different toxins, including amatoxins, orellanine, muscarine, illudins, and coprine. These toxins can cause adverse effects such as liver failure, bradycardia, chest pain, seizures, gastroenteritis, intestinal fibrosis, renal failure, erythromelalgia, and rhabdomyolysis.
The symptoms of mushroom poisoning can vary depending on the type of toxin ingested. Some common symptoms include gastrointestinal discomfort, vomiting, diarrhoea, abdominal pain, nausea, and increased salivation, perspiration, and tearing. More severe symptoms can include organ failure, liver failure, and death.
The best way to avoid mushroom poisoning is to refrain from consuming wild mushrooms. If you do choose to forage for and consume wild mushrooms, it is important to familiarize yourself with both edible and toxic mushroom species to avoid misidentification.
If you experience any symptoms of mushroom poisoning, seek medical attention immediately. Provide as much information as possible about the mushrooms you consumed, including their physical characteristics and the location where they were foraged. This will help medical professionals identify the type of mushroom and provide appropriate treatment.
