Take Home Points:
- Gastrointestinal symptoms lasting longer than or beginning after 6 hours are worrisome
- Most ingestions of “little brown mushrooms” by children result in only mild symptoms
- Misidentification of mushrooms while foraging is most likely to cause toxicity
- Call Utah Poison Control Center at 1-800-222-1222 for any mushroom exposure
Mushroom ingestions are fairly common and have very good outcomes in most scenarios. However, accidental ingestion of hepatotoxic mushrooms may lead to liver failure and death. Though definitive mushroom identification is rarely possible, most patients can be easily identified and treated based on clinical symptoms and laboratory findings.
The Death Cap Mushroom
There is an enormous variety of mushrooms with 15 separate classes of toxic mushrooms commonly described1.
Many “toxic” mushrooms cause only mild GI irritant effects. However, the most notorious of these toxic species are the amatoxin-containing mushrooms which are found in several different genera.
Amanita phalloides, or the so-called death cap mushroom, is an amatoxin-containing mushroom responsible for the majority of deaths in the United States2. It is native to Europe but that is now found in many places in the United States including the Pacific coast, northern Midwest states, and the Northeast. The Utah Poison Control Center is unaware of any confirmed cases ever occurring in the state though local mycologists do report finding such mushrooms in Utah.
Amatoxins are cyclopeptides that inhibit RNA polymerase II in hepatocytes leading to hepatocellular necrosis. The first clinical manifestations of toxicity are significant gastrointestinal distress with vomiting and diarrhea beginning about 6 hours after ingestion. Elevation of AST and ALT occur at about 24 hours and may progress to fulminant hepatic failure over the next few days. Management of A. phalloides induced liver failure is beyond the scope of this article.
Clinical Evaluation of Mushroom Exposure
The history of mushroom exposure and timing of clinical symptoms are the most important components of evaluating patients who have ingested mushrooms.
Many mushroom species cause mild gastrointestinal symptoms but they do so very soon after ingestion. This is in contrast to hepatotoxic mushrooms that do not cause symptoms until at least 6 hours after exposure. Thus a patient with mild nausea and vomiting soon after mushroom ingestion is very unlikely to have consumed a hepatotoxic mushroom. However, it is important to note that patients who foraged for mushrooms could have ingested multiple species with different patterns of toxicity. Thus if symptoms begin after or persist for > 6 hours this may be evidence of a toxic mushroom exposure.
Children consuming “little brown mushrooms” found in the yard can be managed similarly.
Fortunately serious outcomes from mushroom ingestion are rare. The vast majority of mushroom exposures in the United States cause only minor effects2.
Identification of mushrooms is difficult even for trained experts. Given the vast array of toxic mushrooms, there are no definitive methods for identification by foraging enthusiasts such as the area where the mushroom was growing, nearby trees, presence of gills, or color of the mushroom. Those wishing to collect wild mushrooms must have the knowledge to definitely identify the intended mushroom and distinguish it from similar inedible or toxic species. The Mushroom Society of Utah is an excellent resource.
In cases of mushroom ingestion, the poison control center may be able to work with local mycologists to identify a sample of the mushroom. If a patient brings an intact mushroom or vomits a large fragment of mushroom, it may be kept in a paper bag in a refrigerator. Photos of the mushroom should be taken from several angles to include the various parts of the mushroom including the top (cap), underside, and stem. Details about the mushroom the patient intended to gather and where it was found may be helpful. The Utah Poison Control Center can work with local mycologists to identify the mushroom.
Even positive identification of a non-toxic mushroom does not exclude the possibility of ingestion of a toxic mushroom. In many cases, multiple species of mushroom are collected and ingested and the specimen identified may not be the same as the mushroom ingested.
Most mushroom ingestions cause minimal effects or only mild, self-limited gastrointestinal symptoms. Symptoms beginning after or persisting beyond 6 hours should raise concern for a more serious ingestion. The Utah Poison Control Center is available 24 hours a day, 7 days a week for expert consultation on the management of suspected mushroom exposures.
Author: Michael Moss, MD, Medical Director, Utah Poison Control Center
White J, Weinstein SA, De Haro L, Bédry R, Schaper A, Rumack BH, Zilker T. Mushroom poisoning: A proposed new clinical classification. Toxicon. 2019 Jan;157:53-65. doi: 10.1016/j.toxicon.2018.11.007. Epub 2018 Nov 12. PMID: 30439442.
Brandenburg WE, Ward KJ. Mushroom poisoning epidemiology in the United States. Mycologia. 2018 Jul-Aug;110(4):637-641. doi: 10.1080/00275514.2018.1479561. Epub 2018 Jul 31. Erratum in: Mycologia. 2018 Dec 12;:1. PMID: 30062915.