Mushroom toxicity is divided into early toxicity (within 1 h after ingestion) and delayed toxicity (6 h to 20 days). In general, if toxicity begins within 2 h of ingestion of a mushroom, the clinical course will most likely be benign. If symptoms begin 6 h or later after ingestion, however, in general the clinical course will be more serious and potentially fatal. Nearly all fatalities in the United States occur from the ingestion of the Amanita species (Amanita phalloides, Amanita virosa, and Amanita verna).
Mushroom poisoning occurs among four main groups of individuals: young children who ingest mushrooms inadvertently, wild-mushroom foragers, individuals attempting suicide or homicide, and individuals looking for a hallucinatory "high." Identification of the mushroom ingested may be difficult and time consuming. In all cases, treatment should be directed by a patient's symptoms rather than by attempts at mushroom identification. Very often, foragers will mix different species of mushrooms together, so it is not always clear that the species being identified is the same one that was ingested. Treatment of the patients should always be based on presenting symptoms.
Identification of the Amanita species may be helpful; however, there are many Amanita mushrooms that are nontoxic. Amanita species generally have warts on the cap (remnants of the membrane covering the emerging mushroom), which often give it a spotted appearance. The gills are "free," ending before the stem begins. The stem characteristically has a membrane ring around it and widens as it enters the soil. In most cases, the stem of the mushroom is contained in a cup or volva, which may be underground.
This chapter deals with each of the major toxic groups separately, as their toxicity, clinical features, and treatment vary significantly.
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