11
THE POISON PAX
A Deadly Mystery

Not being ambitious of martyrdom,
even in the cause of gastronomical enterprise,
Especially if the instrument is to be a contemptible, rank-smelling fungus,
I never eat or cook mushrooms.

MARION HARLAND, COMMON SENSE IN THE HOUSEHOLD:
A MANUAL OF PRACTICAL HOUSEWIFERY, 1873

What would you call a common mushroom widely eaten across much of Eastern Europe for many generations, which, in spite of its edibility, was the most common cause of mushroom-related sickenings in Poland? What would you call this same mushroom if every now and then dining on it triggered an immediate and severe reaction that included the breakdown of the victim’s red blood cells causing anemia, kidney damage, and occasionally death? If you needed to factor in the reality that those people severely poisoned by the mushroom typically enjoyed an extensive history of eating it with impunity, you would be faced with a mycological mystery. This is the confusing tale of the poison pax, Paxillus involutus, also known as the brown rolled-rim mushroom.

The poison pax is one of the more recent additions to the ranks of mushrooms that were once thought to be benign—even esteemed—as an edible in some regions of the world and are now seen as seriously toxic. It has long been associated with the more minor toxic reactions of gastrointestinal distress in Eastern Europe if eaten raw or undercooked. For a number of years, mushroom experts were aware that this species caused problems when eaten raw, but had not implicated the cooked mushroom. Raw or undercooked Paxillus are frequently responsible for moderate to severe gastrointestinal distress, apparently due to the presence of a heat-labile toxin that is deactivated during cooking.

European mushroom-lovers have a very different attitude than Americans about minor illness caused by mushrooms; they take it in stride as a manageable side effect of enjoying a diverse diet of mushrooms. On several occasions I have talked to European mushroomers who, with a fatalistic shrug, normalize the occasional gastric upset that befalls them in the course of mycophagy.

The recognition of the connection between the poison pax and dangerous severe hemolytic anemia was much more slow in coming. Even after the tentative connection was made, the fact that the anemia struck people following a successful history dining on this mushroom proved to be a major barrier to connecting P. involutus as the causal agent to the hemolytic reaction. Though the mushroom was implicated in other deaths across Europe, following the death of the German mycologist Dr. Julius Schaffer in 1944, serious questions were raised regarding the level of toxicity of P. involutus. Dr. Schaffer and his wife dined on a meal including poison pax after which he rapidly developed vomiting, diarrhea, and fever. Following hospitalization within twenty-four hours, his kidneys, apparently already compromised, began to fail and he died two weeks after his last mushroom meal, despite the fact that Schaffer and his wife had previously enjoyed many meals of poison pax. (Dr. Schaffer is perhaps the only bonafide professional mycologist known to have died of mushroom poisoning.¹ It’s not unusual for people who are passionate about mushrooms—either professional or dedicated amateur—to get sick from eating a mildly toxic mushroom, but rarely will a knowledgeable mycologist eat a really poisonous one.)

The first reports of sudden death by hemolytic anemia associated with eating poison pax were published in the 1960s and attributed the illnesses and deaths to an unknown toxin.² All of the victims who developed hemolytic anemia had eaten poison pax before without any serious problems, although many of them did report gastrointestinal distress after the pax meal they ate immediately prior to the serious poisoning. In the 1970s, German scientists determined that the rapid onset of severe poisoning was attributable to an immune response, and in 1980, the German toxicologist R. Flammer discovered an antigen in the mushroom capable of stimulating a response in the human immune system.³⁴

Here is what we now know about the course of poison pax poisoning that ends with severe consequences. For some people, following repeated ingestion of poison pax, the body responds to an unknown antigen in the mushroom and produces immunoglobin-G antibodies that then circulate in the bloodstream. When they eat their next meal of the mushroom—and it can be many months later—antibody–antigen complexes form in the bloodstream. These complexes attach themselves to the surface of red blood cells circulating throughout the body, triggering cell lysis. This rapid breakdown of red blood cells begins within two hours after the meal and what follows is a rapid rise in free hemoglobin in the blood and overall anemia. The resulting rapidly lowered blood pressure can, at times, induce shock, followed by blood clotting in the vascular system. Victims typically complain of lower back pain as their kidneys become overwhelmed attempting to clean the cell fragments and free hemoglobin from the system, which may eventually lead to kidney failure.⁵ Severe cases have led to extensive hospitalizations and, occasionally, death. Rapid intervention to support kidney function and to flush the toxic components from the blood can assist in recovery. By the mid-1980s, central European doctors were using plasma exchange therapy to rid the blood of the antibody–antigen complexes as an effective life-saving method along with rapid response to mitigate the effects of shock.⁶ Poison pax consumption has led to a number of deaths in Europe over the years. The antibody–antigen reaction does not happen often or in many of the people who historically have eaten these mushrooms. This intermittent negative reinforcement leads some rural people in countries such as Poland to continue to eat poison pax in spite of warnings regarding the danger involved.

No deaths have been attributed to poison pax in the United States. However, Michael Beug reports that at least two cases of serious poisoning involving three adults have been reported in the United States over the past thirty years. These cases involved kidney failure and associated symptoms.⁷ One can ask why we would worry about a mushroom, rarely eaten in the United States and with only three reported serious poisonings in over thirty years? Beyond the need to save lives is the need to understand the course poison pax can take so we can treat the victims in these rare cases and because there is a risk that cases may become more frequent in the future. In the Northeast, poison pax is one of a large group of mushrooms and slime molds found growing in wood mulch in increasing numbers or with extended range. Though poison pax is a mycorrhizal species, growing in close symbiotic association with the roots of trees, it appears also to benefit from energy gained by the rotting organic matter in wood mulch. This combination of mycorrhizal and saprobic activity is likely the norm in many mushroom species. In the late fall, I have observed heavy flushes of poison pax fruiting in mulch, generally beneath birch trees or shrubs. In several instances, there were many dozens of caps present in a very small area. The increased abundance may pose a threat to recent Eastern European immigrants, toddlers, and people who eat mushrooms without adequate knowledge about the dangers.

Today, anyone who consults a recently published mushroom guide will learn about poison pax’s toxicity. Field guides published prior to 1980 in the United States and perhaps even later in some Eastern European countries, however, may refer to the risk of gastrointestinal distress, but generally not report the risk of potentially fatal hemolytic anemia. In 1902, Charles McIlvaine stated that P. involutus was “considered to be edible throughout Europe and considered esteemed in Russia.”⁸ Rene Pomerleau refered to this mushroom as “edible” and is representative of mycologists of his time, though some emphasize the need for cooking. Following 1960, it is interesting to see the slow infiltration of initial caution, mixed messages, and finally, in the late 1980s, a clear message regarding toxicity. Here is a sampling of the recommendations of field guide authors over time:

• 1963: “Harmless if cooked, of little value; slightly poisonous to some when raw.”⁹

• 1972: “There are conflicting stories about the edibility of this dull brown plant.”¹⁰

• 1973: “Good edible, but toxic in the raw state. It is recommended to blanch this mushroom in a very large volume of water for a long time and to throw away the strongly coloured cooking water.”¹¹

• 1974: “Edible, but not highly regarded. Reported as highly esteemed in the U.S.S.R.”¹²

• 1977: “ . . . poisonous . . . Nature of toxin—Type III, gastrointestinal. This should be considered as dangerous, since deaths have been reported from it. The toxin is apparently most potent in raw specimens. Other authorities cite poisoning by this species from a gradually acquired allergic sensitivity that can one day suddenly lead to severe hemolysis, shock and acute kidney failure following a meal of P. involutus.”¹³

• 1981: “Although this species is eaten in some places, in other parts of its range it can have a decidedly acid-sour taste. There are reports that it can produce a gradually acquired hypersensitivity that causes kidney failure.”¹⁴

• 1982: “Harmless if cooked, slightly poisonous if eaten raw; best avoided.”¹⁵

• 1986: “Dangerous! It is often eaten in Europe and by transplanted Europeans in America, but it can cause hemolysis and kidney failure if eaten raw and sometimes when thoroughly cooked!”¹⁶

• 1987: “There are conflicting reports regarding the edibility of this mushroom; because of reports of poisonings, we have listed it as a poisonous species.”¹⁷

In general, North American and western European guides published after 1990 give clear cautionary warnings, but not all do. Luigi Fenaroli, the author of a 1998 Italian pocket guide to mushrooms called Funghi, states, “Edible mushroom of good quality (high value), not easily confused with other noxious species. It is also successfully used in the preparation of dried mushrooms. Some authors have signaled the potential toxicity if consumed in its raw state and they recommend eating them only after a cooking period of at least 25 minutes, even though this recurrence has never been reported in the Southern European countries.”¹⁸ Clearly this author has not kept abreast of European mushroom poisoning reports.

I can only hope, given the potentially severe nature of the toxic reaction, that we do not see an increased number of poison pax cases in our hospital emergency departments. As for me—let the record be clear—I do not recommend collecting and eating the poison pax.