Chapter 117: Mushrooms

INTRODUCTION

The diversity of mushroom species is evident in our grocery stores, our restaurant menus, and our environment. The enhanced culinary interest in mushrooms has led to experimentation by young and old—old citizens and our newest immigrants and our young children reaching for what might become an innocuous (common) or a serious (rare) ingestion. Rigor in ­analyzing the possible ingestion is indispensable for those treating a patient who has ingested a mushroom of concern. This chapter offers general information on the most consequential toxicologic groups of mushrooms and emphasizes clinical diagnosis over mushroom identification.

EPIDEMIOLOGY

Unintentional ingestions of mushrooms particularly in children represent a small but relatively constant percentage of consultations requested from poison control centers (Chap. 130). A summary of a quarter century of ­American Association of Poison Control Centers (AAPCC) data reveals that mushrooms represent less than 0.25% of the reported human exposures. Combined data accumulated by the AAPCC and the Mushroom Poisoning Registry of the North American Mycological Association indicates that approximately 5 patient exposures to toxic mushrooms are called into Poison Control Centers or reported to the Registry per 100,000 persons per year. Some variations result from geographic and climatic conditions and mycologic habitats.¹⁴¹ Although the methods of codification of patients with mushroom exposure have changed over the past 35 years, cumulative AAPCC data consistently demonstrate the relative benignity of the vast majority of exposures. The inability of most health care providers to correctly identify the ingested mushroom and the rarity of lethal outcomes are also demonstrated by the accumulated data. In 75% to 95% of ­exposures, the exact species was unidentified¹⁴¹ (Chap. 130). More than 50% of exposed individuals had no symptoms. Most patients were treated at home and rarely had major toxicity. During the 35 years covered by the AAPCC data, fewer than 100 patients died of their mushroom ingestion. Of the mushrooms associated with death, most were Amanita spp and several were hallucinogens, Boletus spp, or gyromitrin-containing mushrooms, while others remained unidentified. All reported deaths occurred in adults. Those containing either hallucinogens or gastrointestinal (GI) toxins were the most common reported exposures, yet they accounted for less than 10% of all mushroom exposures. All other presumed exposures represented less than 2% of those actually identified. A distinctly different analysis is presented by a retrospective study from the Krakow ­Department of Medical Toxicology suggesting that following mycological analysis 87% of their 457 adult poisoning cases over an 8-year period were related to edible species. They suggested that extended storage in plastic prior to preparation, long storage following cooking, or simply delay to use led to mild gastrointestinal manifestations.⁶⁰ Because more than 75% of mushrooms involved in exposures are never identified—more than 100,000 mushroom species exist, less than 0.1% of these are known to be toxic, and many species are poorly studied—a strategy for making significant decisions with incomplete data is essential.