Mushrooms are a valued food delicacy in many parts of the world, but a number of species can cause harmful effects in humans, in some cases potentially lethal. In recent years the range of recognized clinical syndromes associated with mushroom poisoning has expanded and is now well beyond the scope of past classification schemes. Here, we construct a new diagnostic algorithm based on an updated and comprehensive classification of mushroom poisoning.

We surveyed the available literature through a PubMed search spanning 1927–2018 using the terms “mushroom” and “poisoning” in all possible variations, identifying 1923 papers, from which we extracted those detailing distinct clinical syndromes. We focused on papers published following the major 1994 review by Spoerke and Rumack (subset of 858 papers), particularly noting papers describing “new” syndromes of mushroom poisoning. New syndromes were considered eligible for inclusion into the classification system if there was sufficient detail about both causation and clinical descriptions. Considered criteria included: identity of mushrooms, clinical profile, epidemiology, and the distinctive features of poisoning in comparison with previously documented syndromes.

We propose 6 major groups, plus subgroups based on an analysis of key clinical features that might be relevant in distinguishing between poisoning syndromes. Some clinical features, notably gastrointestinal symptoms (nausea, vomiting, diarrhoea), are common to many types of mushroom poisoning, and it is important that any diagnostic process acknowledges this, in order to avoid missing these cases during the window of opportunity for treatment. Group 1 - Cytotoxic mushroom poisoning. This group encompasses those types of poisoning where there is specific major internal organ pathology, causing either primary hepatotoxicity, or primary nephrotoxicity: 1A, primary hepatotoxicity (amatoxins); 1B, early primary nephrotoxicity (amino hexadienoic acid; AHDA); 1C, delayed primary nephrotoxicity (orellanines). Group 2 - Neurotoxic mushroom poisoning. This group includes those classic types of mushroom poisoning causing primary neurotoxicity: 2A, hallucinogenic mushrooms (psilocybins and related toxins); 2B, autonomic-toxicity mushrooms (muscarines); 2C, CNS-toxicity mushrooms (ibotenic acid/muscimol); 2D, morel neurologic syndrome (Morchella spp.). Group 3 - Myotoxic mushroom poisoning. This group covers mushroom poisoning with rhabdomyolysis as the primary feature: 3A, rapid onset (Russula spp.); 3B, delayed onset (Tricholoma spp.). Group 4 - Metabolic-toxicity mushroom poisoning. This group includes a wide variety of poisoning syndromes and clinical presentations, so could be considered a grouping assembled for convenience, rather than reflecting close clinical similarities: 4A, GABA-blocking mushroom poisoning (gyromitrins); 4B, disulfiram-like (coprines); 4C, polyporic mushroom poisoning (polyporic acid); 4D, trichothecene mushroom poisoning (Podostroma spp.); 4E, hypoglycaemic mushroom poisoning (Trogia venenata); 4F, hyperprocalcitoninemia mushroom poisoning (Boletus satanas); 4G, pancytopenic mushroom poisoning (Ganoderma neojaponicum). Group 5 - Gastrointestinal irritant mushroom poisoning. This group includes a wide variety of mushrooms that cause gastrointestinal effects without causing other clinically significant effects. This latter distinction is important, because many types of mushroom poisoning cause gastrointestinal effects in addition to their primary toxicity effects. Group 6 - Miscellaneous adverse reactions to mushrooms. This group contains those types of mushroom “poisoning” which do not fit within the previous 5 groups. Not all are due to specific “poisoning” reactions: 6A, Shiitake mushroom dermatitis; 6B, erythromelagic mushrooms (Clitocybe acromelagia); 6C, Paxillus syndrome (Paxillus involutus); 6D, encephalopathy syndrome (Pleurocybella porrigens).

We analysed the clinical profile for each group and subgroup of mushroom poisoning, based on a matrix of clinical symptoms/signs and from this developed a diagnostic algorithm, in 6 sections, to allow separation of each poisoning syndrome, with priority placed on those syndromes which were either most severe, or most common. The diagnostic algorithm is intended to be effective for single syndrome poisoning; where ingestions of multiple types of mushroom occur, resulting in a mixed poisoning syndrome presentation, it is impractical to expect a diagnostic algorithm to distinguish each participating syndrome, but it should identify syndromes of concern.

The proposed new classification of mushroom poisoning is the result of our considered efforts to create an organised strategy to assist patient care decisions. We anticipate that new types of mushroom poisoning may emerge and incorporation of these within the classification may require future modification of the scheme and the diagnostic algorithm. The real test for the proposed system will be clinical use.