Mushroom toxicity is a worldwide concern. The increased use of mushrooms as components of organic diets, for alternative therapies, and by unsupervised children accounts, in part, for the renewed interest in mycetism. While most mushroom ingestions do not cause a clinically significant toxidrome, the lethal potential of a select few make mushroom toxicity an important subject. The incidence of mushroom poisoning in the US peaks in accordance with regional mushroom growing seasons, and case frequency has increased on the West Coast. Ingestion is the most common route of entry, but intravenous injection of mushroom toxins and inhalation of mushroom spores have been reported.
Mushroom toxidromes may be classified according to toxin and clinical presentation. Mushroom toxins have been divided into the following 7 main categories:
Amatoxins (cyclopeptides)
Orellanus (Cortinarius species)
Gyromitrin (monomethylhydrazine)
Muscarine
Ibotenic acid
Psilocybin
Coprine (disulfiramlike)
Some authors have created an eighth category comprising a vast range of species that only cause gastrointestinal symptoms.
Amanitin phalloides syndrome or Mycetismus choleriformis accounts for 90-95% of all fatalities from mushroom poisoning in North America. This discussion follows a clinical format because the offending mushroom is frequently unavailable for identification and poisoning may occur from a single species or a combination of different species. Trestrail's data indicate that the mushroom was available for identification in only 3.4% of exposures.
Query patients presenting to the emergency department with compatible clinical scenarios about mushroom ingestion. Even a small piece of a toxic mushroom may cause death. Cooking, salting, or drying does not inactivate all mushroom toxins, and cooking fumes from certain species can cause poisoning.
Pathophysiology: Each mushroom group exerts its toxic effect by a different mechanism, and certain toxins have a predilection for individual organ systems. The amatoxins (cyclic octapeptides), which include amanitin, verotoxin, and phalloides, cause severe hepatocellular damage by inhibiting RNA polymerase II, thereby inhibiting protein synthesis at the cellular level, causing cell death. Other organ systems with high turnover rates (eg, gastrointestinal tract, kidneys) also are affected severely. Ibotenic acid and muscimol bind to glutamic acid and GABA receptors, respectively, and thereby interfere with CNS receptors. Monomethylhydrazine (MMH) from gyromitrin-containing mushrooms affects the GI tract, liver, and kidneys by inhibiting pyridoxine-dependent pathways in the synthesis of GABA. Muscarine affects the autonomic nervous system. It acts through depolarization of muscarinic acetylcholine receptors and exerts a peripheral cholinergic effect through stimulation of the postganglionic parasympathetic receptors. Coprine inhibits aldehyde dehydrogenase, producing a disulfiramlike reaction in those consuming ethyl alcohol. Psilocybin indole exerts its effect on the central nervous system by stimulation of serotonin receptors. Orellanine and orelline, the bipyridyl toxins isolated from Cortinarius orellanus, exhibit their nephrotoxic effects by inhibiting alkaline phosphatase of the proximal tubule cells. Genetic factors may contribute to the clinical manifestations of this toxin, which has toxicity that is not reduced by cooking or drying.
History:
Try to ascertain the species or varieties of the wild mushrooms ingested, the type of preparation, volume ingested, and symptoms of others sharing the mushroom meal. Comorbidity, concomitant medications, allergies to medications, and drug and alcohol use may influence the clinical picture and should be elicited. Symptoms and signs are discussed relative to onset postingestion, with gastrointestinal dysfunction being a nearly universal component. Early symptoms may be observed with mixed ingestions, and they do not exclude a potentially fatal poisoning.
A short latency period (30-180 min) may be observed with GI mushroom (eg, Chlorophyllum molybdates, Entoloma lividum, Boletus species, Paxillus species) syndromes, muscarine-containing mushrooms (Inocybe species, Clitocybe species), psilocybin-containing mushrooms (Paneolus species, Psilocybe species, Gymnopilus species), and coprine-containing mushrooms.
GI mushroom syndromes present exclusively with abdominal discomfort, cramping, nausea, vomiting, and/or diarrhea. Dehydration is the most common complication. Most symptoms resolve by 24 hours and the prognosis is generally good.
Anticholinergic symptoms can occur with ibotenic and muscimol ingestions. Dizziness, incoordination, ataxia, GABAergic effects, seizures, hallucinations, muscle spasms, flushing, and dilated pupils may be observed.
Cholinergic effects may result from muscarine ingestion. Perspiration, salivation, lacrimation, blurred vision, miosis, hypotension, bradycardia, and bronchoconstriction have been described. Although muscarine was first isolated from the Amanita muscaria mushroom in 1868, the signs and symptoms of poisoning from A muscaria are not related to muscarine.
Neuropsychiatric symptoms, including hallucinations or delirium, have been associated with mycetism caused by ibotenic acid, muscimol, and psilocybin. Muscle weakness, drowsiness, hallucinations, hyperkinesis, and mydriasis have been described. Patients may have hallucinations while awake and then have a prolonged sleep that lasts hours; in each case, the prognosis is generally good and symptoms resolve within 24 hours with supportive care. Rare residual effects have been reported.
Muscarine and coprine intoxications have also been associated with neurovegetative symptoms.
The Coprinus syndrome is characterized by a rapid onset of nausea, vomiting, tachycardia, palpitations, paresthesias, diaphoresis, and flushing. Hypotension also can occur. This syndrome has been referred to as a disulfiramlike reaction; it is associated with ethanol use from 30 minutes to 5 days following a mushroom meal, and symptoms generally last 2-4 hours. Interestingly, if alcohol is consumed at the time of the mushroom meal, symptoms may not occur.
Intravenous injection of mushroom toxins from Psilocybe species has been reported. The clinical course includes vomiting, fever, muscle cramps, and hypoxia.
A long latency period (>6 h) can be observed with amatoxins, orellanus, and gyromitrin syndromes. This generally signifies a serious ingestion and should be considered potentially life threatening.
Amatoxin toxicity presents in the following 3 stages.
Stage one presents with abdominal cramping, nausea, vomiting, and profuse watery diarrhea after a latent period of 6-12 hours.
The second stage begins with clinical recovery of gastrointestinal dysfunction after 24 hours and lasts 2-3 days, during which liver damage is ongoing.
In the third stage, hepatic and renal damage becomes clinically evident.
Orellanine toxicity initially may present with gastrointestinal dysfunction 24-48 hours postingestion of mushrooms from the genus Cortinarius. Acute renal failure may follow from 36 hours to 2 weeks postingestion and present with flank pain, polydipsia, polyuria, oliguria, and malaise.
Gyromitrin toxicity typically presents 6-10 hours postingestion (but may be delayed up to 48 h) with gastrointestinal dysfunction. Patients may display symptoms and signs of volume depletion, hepatic injury, methemoglobinemia, intravascular hemolysis, and CNS effects (eg, malaise, tremor, myoclonus, delirium, seizures, encephalopathy).
Lab Studies:
Consider the following tests for an initial laboratory evaluation of a symptomatic patient in the emergency department:
As with all suspected toxic ingestions, blood, urine and gastric contents should be saved.
Consider CBC, urinalysis, coagulation studies, glucose, BUN, creatinine, electrolytes, fibrinogen, and arterial blood gas as possible the initial tests.
If the patient has evidence of hemolysis, haptoglobin and Coombs tests may be helpful.
Perform clotting studies and conduct hepatic and renal profiles if phalloides syndrome is suspected.
In Gyromitra species intoxications, a methemoglobin level may be indicated.
Identify the mushroom whenever possible. This may be done with the help of a regional Poison Control Center, the consulting mycologist, or by referring to the Poisindex or a mycology handbook.
If the mushroom is available, the following information may be helpful for determining the mushroom's identity:
Provide the mycologist with all available information, including the size, shape, and color of the mushroom. Be able to describe the surface and the underside of the cap, the stem, gills, veil, ring, spores and the color and texture of the flesh. If the specimen is not available for the mycologist to examine personally, cut the specimen to see if the gills are attached to the stalk. It also is helpful to know the location and conditions in which the mushroom grew (eg, wood, soil).
Wrap the mushroom in foil or wax paper and store in a paper bag in a cool dry place, pending transport to your mycologist. Do not store in a plastic bag or container because the moisture may alter the mushroom's features. Do not freeze.
Consider making a spore print using a piece of black and white paper. To make a spore print, remove the stem and place the mushroom cap, gill side down, on the paper. Cover with a bowl to prevent disturbance. Wait at least 4 hours and evaluate the print, noting the pattern and color. Fix the print with artist's fixative or hair spray. Amanita varieties have white spores. Immature mushrooms may not shed spores.
The Meixner test (a qualitative bedside assay) is used to detect amatoxins (eg, alpha-amanitin, beta-amanitin) in the mushroom. It is not recommended for use with stomach contents nor to determine edibility of a mushroom because false-positive and false-negative results have been described.
If the mushroom is unavailable, the following information may be helpful for determining the mushroom's identity:
Save emesis or gastric lavage fluid for microscopic examination for spores. If mushroom fragments are available, they can be stored in a 70% solution of ethyl alcohol, methanol, or formaldehyde and placed in the refrigerator. Otherwise, emesis can be centrifuged and the heavier layer on the bottom can be examined under a microscope for the presence of spores.
Consider high performance liquid chromatography for quantification of alpha or beta amanitin in urine, plasma, or gastric contents.
Consider the amanitin radioimmunosorbent assay kit to detect alpha-amanitin in blood if used within 24 hours postingestion. False-positive results have been reported.
Prehospital Care: If it is known that mushroom ingestion has occurred, make every attempt to supply the hospital personnel with any remaining sample of the mushrooms involved. This may involve saving the patient's emesis. Otherwise, care is supportive (eg, intravenous hydration for volume depletion, pharmacologic sedation for agitation).
Emergency Department Care:
Asymptomatic patients
Obtain specimen, if possible, of mushroom or emesis.
Contact a regional poison control center.
Give 1 g/kg of activated charcoal orally.
Encourage fluids and administer a balanced diet.
Monitor patients in the emergency department for at least 4 hours. Discharge patients home if they continue to be asymptomatic and can be contacted and reliably monitored at home. Advise patients to contact the hospital immediately if they become symptomatic. If the mushroom is identified as potentially toxic or the patient becomes symptomatic, admission to the hospital is recommended.
Symptomatic patients
The basic elements of supportive care are critical in the evaluation and management of the poisoned patient. Attention to airway maintenance, breathing, and adequacy of circulation should be ongoing.
Provide intravenous glucose to obtunded patients as a priority. Dextrostix evaluation can help guide therapy initially.
Obtain the mushroom specimen, if possible, and facilitate expeditious transport to mycologist.
Consider gastric lavage followed by activated charcoal administration every 2-6 hours. Airway protection is critical in these patients because of the risk of aspiration.
Cardiopulmonary monitoring should be continuous.
Monitor fluid, electrolyte, and glucose status; correct accordingly. Rehydrate with isotonic fluids. Forced diuresis is not recommended.
If amanitin ingestion is suspected or proven, careful attention to clotting studies and renal and hepatic profiles is important. Early consultation with a medical toxicologist is recommended.
If symptoms or laboratory parameters become critical, admit the patient to a critical care unit and consider specific treatment options.
Additional treatment options may be considered under the following circumstances:
For anticholinergic symptoms consistent with ibotenic acid or muscimol, consider physostigmine administration. This option should be used only for life-threatening anticholinergic signs and symptoms. It may cause bradycardia, asystole, or seizures. Atropine and emergency resuscitation equipment should be available immediately at the bedside.
Consider atropine administration for cholinergic effects consistent with muscarine.
Disulfiram effect consistent with coprine may require cardiac dysrhythmic medications (eg, beta-blockers) or fluids and catecholamine infusions (eg, norepinephrine, dopamine) for severe hypotension.
Hallucinations or delirium consistent with muscimol, ibotenic acid, or psilocybin usually responds to reassurance and a quiet environment; however, benzodiazepines may be necessary. Atropine may exacerbate these symptoms.
Amatoxin syndrome merits special attention because it is responsible for the most serious morbidity and mortality in mycetism. Although specific antidotes and controlled clinical trials do not exist, anecdotal and animal studies suggest a potential benefit of high dose penicillin, silibinin (a constituent of the extract silymarin derived from the milk thistle, Silybum marianum), cimetidine, aucubin (an iridoid glycoside of Aucuba japonica), and kutkin.
Intravenous pyridoxine may be considered for MMH induced coma or seizures refractory to standard treatment.
