A narrative review of toxicity after exposure to true morel (Morchella genus) and false morel (Gyromitra genus) mushroom ingestions.

Introduction: The clinical presentations associated with Morchella spp. (true morel) and Gyromitra spp. (false morel) mushroom ingestions are incompletely characterized. The objective of this review is to describe the clinical presentations reported after Morchella spp. and Gyromitra spp. ingestions.

Methods: This is a narrative review to identify studies reporting toxicity in humans from Morchella spp. and Gyromitra spp. The literature search was performed in two stages. First, a search of Medline, Embase, PubMed, Scopus, and Agricultural & Environmental Science electronic databases was performed. The search strategy employed a combination of controlled vocabulary terms and free-text terms. Terms such as "morel," "true morel," "false morel," "morchella," "gyromitra," and "lorchel" were utilized in conjunction with keywords related to toxicity. Duplicate articles were removed. Second, a manual search of the references for the included articles was performed. Inclusion criteria were peer-reviewed human reports of mushroom ingestion in all languages up to 31 December 2024, with sufficient description of three components: acute ingestions to Morchella spp. or Gyromitra spp., clinical manifestations, and medical outcome.

Results: There were 84 articles that met the inclusion criteria. The articles described 201 and 52 individual Gyromitra spp. and Morchella spp. ingestions, respectively. The mortality rate in these articles was 28.9% for Gyromitra spp. and 7.7% for Morchella spp. The clinical presentation after Morchella spp. ingestion was primarily neurologic (65.4%), most commonly dizziness and/or unsteadiness/ataxia (51.9%), without any reported seizures, with a median onset of 12 h (IQR: 9-12 h). Gastrointestinal (50.0%) effects were less common and often early, with a median onset of 2.3 h (IQR: 1.1-9 h). Hepatic effects were uncommon (17.3%) and only present when other organ systems were involved. No fatalities from Morchella spp. ingestion were reported until 2024. However, three articles published in 2024 report multiple cases of critical illness and fatality after Morchella spp. ingestion. The clinical presentation of Gyromitra spp. ingestions was primarily gastrointestinal (88.1%) and often delayed with a median onset of 9 h (IQR: 6-12 h). Hepatic (53.7%) and neurologic (51.7%) effects were also commonly reported. Seizures were only reported in 13.9% of Gyromitra spp. ingestions and mostly in fatal cases (82.1%) later in the disease course. Hemolysis was reported in only a minority of Gyromitra spp. (2.5%) ingestions.

Discussion: Morchella spp. ingestions were most frequently associated with a constellation of neurologic symptoms, including dizziness, unsteadiness, and ataxia. Approximately half of the patients displayed gastrointestinal symptoms, typically within the first 6 h. The absence of gastrointestinal symptoms did not preclude the involvement of other organ systems. However, the recent critical and fatal cases of Morchella spp. ingestion display a pattern of severe, early vomiting and diarrhea, sometimes with shock, hemorrhagic gastrointestinal complications, and multi-system organ failure. Gyromitra spp. ingestions commonly displayed delayed gastrointestinal, hepatic, and/or neurologic effects. However, seizures were uncommon other than in the late stages of fatal cases with coma. This review has limitations, including reporting and publication biases. However, having a better understanding of what has been reported in the literature provides better insight into these rare toxicologic presentations.

Conclusions: The clinical presentations following the ingestion of Morchella spp. and Gyromitra spp. mushrooms reported in the literature follow distinct patterns that differ from what is commonly reported in reference texts. Morchella spp. ingestions were associated with a constellation of neurological symptoms, including dizziness, unsteadiness, and ataxia, and many patients developed gastrointestinal symptoms, which typically occurred within 6 h. Several reports in 2024 described cases of critical illness, including early gastrointestinal symptoms, sometimes with shock, hemorrhagic gastrointestinal complications, and multi-system organ failure. Toxicity after Gyromitra spp. ingestion typically results in delayed gastrointestinal symptoms followed by hepatic and neurologic effects. Seizures were mostly reported as late findings in fatal cases after the onset of coma and multi-organ injury.