Foraging for edible wild mushrooms is becoming increasingly popular say the authors of a case study of a woman who had to have a liver transplant after ingesting mushrooms she thought were safe to eat.

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The authors warn that poisonous and edible mushrooms can be very similar in appearance.

Dr. Adina Weinerman of Sunnybrook Health Sciences Centre in Toronto, Canada, and colleagues explain how eating the wrong mushrooms can result in liver failure and even death.

Even fungus experts can find it hard to distinguish mushrooms that are safe to eat from harmful ones, they note in a paper published in the Canadian Medical Association Journal.

There is no antidote for mushroom poisoning. The authors recommend doctors caring for patients with the condition should treat it aggressively, monitor the liver closely, and ask a poison control center about additional treatments. They should also investigate liver donation in case of liver failure.

If administered promptly, charcoal can absorb mushroom toxin. But unfortunately, because symptoms take time to appear, patients present themselves at emergency departments too late for this to be effective.

The true incidence of mushroom poisoning is hard to quantify because of the likely high number of unreported cases. The authors say in the US around 6,000 cases are reported annually, most of which are associated with mild symptoms.

Mushroom poisoning is more common in Western Europe, where around 50-100 deaths are reported every year.

In their paper, the authors describe the case of a 52-year-old immigrant Asian woman living in Canada who had been picking wild mushrooms in a local park with her husband, who used to forage for wild mushrooms in his native country.

The woman – who had been healthy before experiencing sudden abdominal pain, nausea, vomiting and watery diarrhea – eventually required a liver transplant.

She had eaten the mushrooms 12 hours before attending the emergency department. She brought some of the mushrooms with her to the hospital: they were Amanita bisporigera, a highly toxic species.

There are over 600 types of Amanita fungi, and they cause the most deaths from mushroom poisoning.

Mushroom poisoning proceeds through three phases. The first phase occurs 6-24 hours after ingestion and produces stomach and gut pain, nausea, vomiting and diarrhea.

The second phase is a “false recovery” phase where the symptoms seem to go away and the patient feels better. The authors warn this can lead to premature discharge from the emergency department or hospital.

In the third and final phase of mushroom poisoning, which usually occurs around 48 hours after ingestion, liver failure sets in, followed by multi-organ failure and even death.

In 2013, experts from Rutgers New Jersey Medical School warned that the growing popularity of wild mushroom foraging in the US may lead to increased hospitalizations and serious illness. The majority of reported cases of mushroom poisonings, they said, were of immigrants who were used to foraging in their native lands.

The Canadian authors of this latest paper make the same observation and conclude:

Patients should be counseled that poisonous and edible mushrooms can be very similar in appearance and that wild mushrooms of uncertain identity should not be eaten. This information is especially important for immigrants who might mistake local poisonous mushrooms for familiar edible species from their native land.”

They urge people to report cases of mushroom poisoning to the appropriate authorities so the toxic fungi can be located and further cases prevented.

The North American Mycological Association have an online form where you can report cases of mushroom poisoning.

In their guide to mushrooming (resource no longer available at mdc.mo.gov), the Missouri Department of Conservation recommend you do all of the following if you forage for edible wild mushrooms:

  • Join a mushroom club and go on forays and workshops
  • Learn about mushrooms and how to identify them
  • Use several field guides – one picture is not enough – and read the details carefully
  • Show your finds to experts
  • Don’t let your nose guide you – poisonous mushrooms can smell and taste good too
  • Collect and identify what you think is the same species again and again
  • Learn how mushrooms from the same species can look very different as they mature and in different seasons
  • And learn how mushrooms from different species can look very similar – a common cause of mushroom poisoning is green-spored Lepiota (Chlorophyllum molybdites), young specimens of which look just like the common white button mushrooms you can buy