Toxic Mushrooms

Inna Baran MD
Jason Hack MD
Brown University, Medical Toxicology

There are at least 10,000 species of mushrooms and approximately 50 to 100 of these are known to be poisonous. Typically, mushroom poisoning occurs when recent Asian or Eastern European immigrants mistake poisonous mushrooms for edible ones, when young adults ingest mushrooms for recreational purposes, or when children take a bite of a mushroom found in their backyard.

In order to identify the ingested mushroom, it is essential to obtain a detailed description of the mushroom and to discuss with a mycologist (through your Poison Control Center). An option to consider is gastric aspiration, however this is often poorly tolerated by patients. Often, the specific mushroom is only identified after treatment is initiated, and it usually remains unidentified. Given the large number of different species and how rarely the specific species is identified, classification is typically done by clinical syndrome. There are 14 different clinical syndromes ranging from gastrointestinal upset to hallucinations to fulminant hepatic failure. Many of these syndromes are treated symptomatically with supportive care, though a few have more specific treatments.

Toxic mushroom ingestions can cause symptoms such as rhabdomyolysis, renal failure, liver failure, seizures, or encephalopathy. If seizures do not respond to benzodiazepines, pyridoxine may be considered. The treatment for the majority of toxicities is supportive care given that many patients present with nausea, vomiting and diarrhea. Additionally, a single dose of activated charcoal should be strongly considered for awake patients. If there is any concern about delayed hepatotoxicity, additional doses of activated charcoal may be administered.

One of the most notorious mushroom toxicities results from Cyclopeptides such as ɑ-Amanitin found in the Death Cap mushroom (among others). ɑ-Amanitin acts by interfering with RNA polymerase II preventing DNA transcription and leading to apoptosis. Symptoms begin ~ five hours after ingestion, starting with gastrointestinal symptoms followed by hepatic failure, encephalopathy, and death in up to 30% of cases. ɑ-Amanitin is known to undergo enterohepatic circulation, so multiple doses of activated charcoal are often administered. Silibinin, a derivative of Milk Thistle, appears to be the most efficacious of available treatments. The IV form is preferable but may be difficult to obtain, so when unavailable, the oral form can be found over-the-counter at health food stores. Silibinin reportedly works by preventing hepatocellular uptake of the toxin. Penicillin reportedly has a similar mechanism of action, and has been used as a treatment; however its benefit has not been clearly demonstrated. N-Acetyl Cysteine has also been used as a treatment given its effects as an anti-oxidant.

In the case of an unknown mushroom exposure, the most important factor to consider is the risk of delayed toxicity such as in the case of the previously mentioned Cyclopeptide toxicity. Typically the most toxic mushrooms cause delayed symptoms five or six hours after ingestion. One exception to this is the renal failure caused by the Amanita Smithiana mushroom. The good news for the majority of the country is that this mushroom is found exclusively in the Pacific Northwest. Another exception is in the case of ingestion of multiple mushrooms or at multiple meals at which point the timing of symptoms becomes less clear.

If a patient meets any of the following criteria, they should be admitted for observation: symptoms that begin after five hours of ingestion, early symptoms that persist after five hours, consumption of more than one mushroom or at more than one meal, evidence of rhabdomyolysis, evidence of renal or liver damage, if there is suspicion of amatoxin ingestion or lack of reliable 24 hour follow-up. If good follow-up within 24 hours can be obtained, if the patient is symptom free, if a minimal amount was ingested, or if early symptoms resolved and toxic mushroom ingestion can be excluded by clinical syndrome, history or mushroom identification, the patient can likely be discharged.

In summary, classification of poisoning in the case of mushroom toxicity is by clinical syndrome. Lethal mushrooms typically present with symptoms that begin after five hours, except as described, in the Pacific Northwest. If possible, obtain mushroom samples and contact a local toxicologist or the Poison Control Center.

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