A 25-year analysis of Armillaria (honey mushroom) poisoning in Wisconsin.

BACKGROUND: Wild mushroom foraging is common in the United States. Poisoning usually results from misidentification, though some "edible" mushrooms can also cause toxicity. Armillaria ("honey mushrooms") are widely foraged and generally considered edible, yet sporadic gastrointestinal illness has been reported. Their clinical effects remain poorly described. Poison center data provide real-world exposure characterization with standardized symptom documentation and mycologist collaboration. This study characterized the presentation, management, and outcomes of suspected or confirmed Armillaria ingestions reported to the Wisconsin Poison Center (WPC) over 25 years.

METHODS: We conducted a retrospective case series of WPC records (2000-2025). Cases coded as Armillaria, "unknown mushroom," or "gastrointestinal irritant mushroom" were screened. Inclusion required mycologist confirmation or patient-reported Armillaria ingestion.

RESULTS: Eighteen cases were identified; 50% (n = 9) had mycologist confirmation. Exposures occurred August-October, with 78% in late September-mid-October. Most patients were adults (94%), median age 41.5 years. Fifteen (83%) developed gastrointestinal symptoms (vomiting, diarrhea, abdominal pain, nausea); all symptomatic patients had vomiting or diarrhea. Three (17%) remained asymptomatic. Symptom onset ranged 0.25-7.5 h (median 3.5), with resolution in 2-41 h (median 8.75). Five patients (28%) were evaluated in an emergency department; four were discharged and one had a brief admission for symptom control. No organ failure or deaths occurred. Illness occurred despite reported cooking. Concern for misidentification with toxic look-alikes was common; some cases reporting Armillaria were later identified as psilocybin-containing Gymnopilus.

CONCLUSIONS: Armillaria ingestion produces a self-limited gastrointestinal toxidrome, typically with early onset but occasionally >6 h, which may complicate differentiation from amatoxin-containing species such as Galerina. If patients report Armillaria ingestion toxic look-alikes, including Gymnopilus, Galerina, Cortinarius, and muscarine-containing genera, should remain in the differential if appropriate toxidrome features are present. Confirmed cases generally have a favorable prognosis. Early poison center or toxicology consultation can assist with identification and management.