Mushroom Poisoning: A Deadly Mistake

Mushrooms are an important source of food and medicine, especially in China. However, some mushrooms are toxic and can cause poisoning, leading to severe illness and even death. Poisonous mushrooms contain toxins that can affect multiple organs, including the liver, kidneys, and brain. While most cases of mushroom poisoning are not severe, certain types of mushrooms contain very potent toxins and are highly poisonous, resulting in high mortality rates even with prompt treatment. The number of deaths from mushroom poisoning varies across regions, with an average of about 3 deaths per year in the United States and an estimated 50-100 deaths each year in Europe and China.

Death cap mushrooms

Due to the deadly nature of death cap mushrooms, it is essential to be able to identify them correctly. They are often mistaken for edible puffballs or other Amanita species, so some experts recommend avoiding collecting Amanita mushrooms for consumption altogether. It is crucial to seek immediate medical attention if you suspect that you or someone you know has ingested death cap mushrooms, as prompt treatment significantly improves survival rates.

Amanita phalloides

The death cap originates in Europe but has since been introduced to other parts of the world, including the western United States and Canada, as well as other areas such as the Northeast. It grows in mixed deciduous woods, often in widely spaced groups, particularly under oak and beech trees. The large fruiting bodies (mushrooms) appear in summer and autumn, with caps that are generally greenish in colour, though the cap colour is variable, and can include white forms. The gills underneath the cap are white, turning cream or slightly pink as they age. The stem is off-white, 7-15 cm high, with a floppy ring, and is swollen at the base.

The principal toxic constituent of Amanita phalloides is α-amanitin, which causes liver and kidney failure. The onset of symptoms typically occurs 6 to 12 hours after ingestion, with colicky abdominal pain, vomiting, and watery diarrhea. These symptoms subside after about a day, but then recur after about 72 hours, along with signs of impending liver failure. Death usually occurs 7 to 10 days after the first onset of symptoms. Early treatment is essential to prevent liver damage and reduce mortality.

Liver and kidney failure

In the United States, mushroom poisoning kills an average of about 3 people per year. According to the National Poison Data System (NPDS), 52 fatalities have been reported over an 18-year period, mostly from cyclopeptide-producing mushrooms ingested by older adults unintentionally. The lethal amanitas produce a toxin called ɑ-amanitin, also known as AMA, which attacks the liver and kidneys and inhibits protein synthesis in these organs. Amatoxin syndrome is the most common intoxication resulting from mushroom poisoning. The onset of symptoms typically occurs 6 to 12 hours after mushroom ingestion, with severe hepatic failure and kidney failure occurring 48 hours or more after ingestion. Renal failure occurs in 30%-75% of all poisonings, depending on individual sensitivity and the amount ingested.

The first stage of amatoxin poisoning includes cholera-like diarrhea, vomiting, and abdominal pain. This is followed by a period of clinical improvement, after which cytolytic hepatitis occurs silently. The third phase, marked by severe hepatic and kidney failure, begins 48 hours or more after ingestion. Patients with kidney failure due to fungal toxin ingestion may present with leukocyturia, hematuria, and proteinuria.

Treatment for amanita poisoning includes N-acetylcysteine, a glutathione precursor with a hepatoprotective effect, and the administration of i.v. benzylpenicillin, vitamin C, and cimetidine. In cases of fulminant hepatic failure, a liver transplant may be required. The prognosis for renal failure is frequently poor, often requiring chronic dialysis or kidney transplantation.

While most mushrooms are not dangerous, poisonings from wild mushrooms occur due to misidentification as edible species. To prevent mushroom poisoning, gatherers should familiarize themselves with both the mushrooms they intend to collect and similar-looking toxic species. Symptoms of mushroom poisoning can vary from slight gastrointestinal discomfort to death within about 10 days.

Cyclopeptide poisoning

Cyclopeptide mushroom poisoning is responsible for 90% to 95% of deaths from macrofungal ingestion. Cyclopeptides are found mainly in species from three genera: Amanita, Galerina, and Lepiota. These mushrooms are found on five continents and grow predominantly in Europe and North America.

The toxins produced by cyclopeptide mushrooms are primarily amatoxins, phallotoxins, and virotoxins. Amatoxins are the only toxins found in common among the three genera and are responsible for organ damage. They irreversibly bind to DNA-dependent RNA polymerase II in eukaryotic cells, causing a progressive decrease in mRNA, leading to a decrease in protein synthesis and cell death. Phallotoxins are extremely potent hepatotoxins but are not well absorbed from the GI tract, so they contribute little to Amanita toxicity following ingestion.

The clinical presentation of cyclopeptide mushroom poisoning, also called phalloidian syndrome, is typically divided into three phases. After a latency period of 6 to 12 hours, sometimes even 24 hours, severe gastrointestinal symptoms appear, including vomiting and diarrhea, and severe dehydration, which can lead to acute kidney injury, electrolyte and acid-base imbalance, and even hypovolemic shock. In Phase II, the patient's clinical condition improves with rehydration, but hepatic cytolysis appears, often asymptomatically. In severe cases, Phase II progresses to Phase III of hepatic and acute renal failure, which can lead to death despite supportive care.

The diagnosis of cyclopeptide mushroom poisoning is made largely from a positive history of ingestion coupled with suggestive physical findings, such as acute gastroenteritis and toxic hepatitis. Treatment for cyclopeptide mushroom poisoning includes fluid/electrolyte resuscitation, liver transplantation in severe cases, and the administration of antidotes such as penicillin G and silibinin, though their effectiveness is not yet fully understood.

Misidentification of toxic mushrooms

Mushroom poisoning is often the result of mistaking toxic mushrooms for edible ones. While most mushrooms are innocuous, a small percentage are poisonous and can cause severe poisoning and even death. The vast majority of mushroom-related deaths are caused by species in the genus Amanita.

The most common reason for misidentification is the close resemblance between toxic and edible mushrooms in terms of colour and general morphology. For example, the toxic “Death Cap” mushroom, Amanita phalloides, can easily fool foragers from countries where it does not exist, but where similar-looking edible mushrooms do. Those most susceptible to mushroom poisoning are often immigrants who mistake local toxic mushrooms for edible ones from their home countries.

To prevent mushroom poisoning, 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 of the methods of preparation for cooking, as some toxins are thermostable and will not be rendered safe by cooking. For example, the Devil's Bolete is poisonous both raw and cooked and can lead to strong gastrointestinal symptoms.

In addition to colour and morphology, other characteristics such as the shape of the mushroom cap have been used to distinguish between edible and poisonous mushrooms. However, these methods are not always reliable. For instance, the belief that "poisonous mushrooms have a pointed cap, while edible ones have a flat, rounded cap" does not hold true for the Death Cap, which has a rounded cap when mature. Similarly, the folklore that "poisonous mushrooms will turn rice red when boiled" led to the hospitalization of several Laotian refugees who ate toxic Russula mushrooms.

While some toxic mushrooms emit an unpleasant smell that discourages consumption, this odour may not always be detectable by humans. Additionally, some mushrooms contain less toxic compounds and may not cause severe poisoning, but certain types contain very potent toxins that can lead to high mortality rates even with prompt treatment.

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