Eating the wrong wild mushroom can be a grave mistake, leading to death or, as in the case of one 52-year old woman in Ontario, to the need for a lifesaving liver transplant.

"Thus far, I have only seen one case of mushroom poisoning during my residency," said Dr. Corey M. Stein, lead author of a case report about the woman in CMAJ. "I imagine that (foraging) is relatively common but most people are not picking poisonous mushrooms so we don't hear about it as physicians."

Stein, of the University of Toronto, and his coauthors describe the condition of the woman, an immigrant of Asian descent who had been foraging in a local park with her husband. She appeared at the hospital with acute abdominal pain, nausea, vomiting and watery diarrhea, about 12 hours after eating the mushrooms.

As she had brought a sample of the mushrooms to the emergency department, experts were able to identify them as Amanita bisporigera, a deadly fungus especially toxic to the liver. Common throughout eastern and central North America, this tall, white, smooth-capped mushroom is also known as the "eastern North American destroying angel."

The patient was initially rehydrated and given regular doses of activated charcoal to help clear the toxins as well as medications to protect the liver, but within two days her liver function worsened and she was transferred for an emergency liver transplant.

Mushrooms of the Amanita genus cause the majority of reported deaths from mushroom poisoning, the authors write in CMAJ. In the U.S. there are about 6,000 reported cases of mushroom poisoning each year, most being mild cases, though many may go unreported, Stein said.

"The Ontario Poison Centre fields on average 200 calls per year on mushroom exposures," Stein told Reuters Health by email.

Foraging is much less common in the U.S. and Canada than in other countries, according to Dr. Tri Tong, an emergency medicine physician in La Jolla, California, who has studied mushroom toxicity.

"Because there are many toxic mushrooms that mimic the appearance of benign ones (that's how nature intended it - it's a defense mechanism), no one should forage alone for wild mushrooms to eat unless they are truly an expert with years of experience," Tong, who was not part of this case study, told Reuters Health by email.

However, he noted, poisoning from pharmaceuticals is hundreds of times more likely than from plants and mushrooms, especially in places like the U.S. and Canada, which are not foraging cultures. In the case of this woman who foraged in the park, little more could have been done to save her liver, Stein said.

"There is no specific antidote for mushroom poisoning," he said. "Many therapies have been studied including N-acetylcysteine (which is an antioxidant used in tylenol overdose) and high dose penicillin but none have been shown to improve outcomes."

The toxin in the mushroom is not made safer by cooking or by freezing, so preparation does not affect the ultimate poisonous outcome, he said.

"I do think that mushroom foraging can be done safely but the general public needs to be aware of the dangers of ingesting the wrong kind of mushroom," Stein said. "Foragers should be advised that poisonous mushrooms and edible mushrooms can look very similar and mushrooms of uncertain identity should not be eaten."

Policymakers and doctors should focus on reminding people that wild mushrooms, despite sometimes growing in environments we consider to be safe, can pose extreme health risks, he said.