Wilderness Medicine Menu: True Morels and False Morel Poisoning
/Disclaimer: I am not a mycologist, I just grew up in the woods and read some books. This is not a mushrooming guide. Consume at your own risk as mushroom misidentification will kill you. Eat only what you are 100% certain is edible. In the words of the legendary Dr. Otten, “There are old mushroom hunters, and there are bold mushroom hunters. But there are no old, bold mushroom hunters.”
Delicacy or Deadly?
A True (O.G.) Morel Mushroom. (Richard Steih, CC BY-NC 2.0, via Flickr)
Morel mushrooms commonly refer to any of the roughly 80 species of edible mushroom in the genus Morchella. These honeycomb-shaped fungi typically appear during March, April and May throughout the Northern Hemisphere. However, to refer to these mushrooms as [just] edible is a bit of an understatement, as these fungi are coveted by gourmet cooks and entire festivals are dedicated to morel “hunting” and gastronomy. Quality shrooms can fetch a street value upward of $20 per pound.
Pale and palate pleasing. (Peter Stevens from Seattle, CC BY 2.0, via Wikimedia Commons)
Dark and delicious. (Owlatlas, CC BY-SA 4.0, via Wikimedia Commons)
When I was in elementary school, my father took me into the woods of northern Michigan for a crash course in Morchella mycology. He taught me about morel identification and how to cook them (you haven’t really experienced surf-n-turf until you’ve had brook trout paired with venison steaks smothered in sautéed morels and mushroom gravy). Worth noting at this point that morel mushrooms are poisonous in their raw form, as they contain varying levels of heat-labile toxins. Roasting, sautéing, baking or boiling will suffice. It is also worth noting that there are commonly mistaken look-a-likes that are quite toxic and land the overconfident in ERs +/- the morgue each year.
Identification
Morels look like upside-down pinecones which exhibit a spongy, porous labyrinth of deeply-ridged craters and pits, as seen on the left below:
Tubular! (“Morel Slice” by Odalaigh, CC BY-NC-ND 2.0, via Flickr)
Easy, right? Maybe not. Their caps vary significantly. They can be fat and stumpy, skinny and slender. They come in many colors: yellow, gray, brown, black and orange.
Ok, so now it seems less straight forward. Good.
Next step, if we want to definitely identify a morel from the poisonous poser, we must get surgical. A mid-sagittal plane with a 10-blade should do the trick.
Morel mushrooms will be completely hollow inside, from cap to stem. Note the cap is hollow. The stem attaches only at the base of the cap. The stem itself is hollow. This makes an entire hollow cavity from root to tip of the cap which is uninterrupted and a unique feature of Morchella. “If it isn’t hollow, don’t swallow”.
The Imposter
False morel (Gyromitra spp., most commonly G. esculenta). This fungus is not you friend. (Toffel, CC BY-SA 3.0, via Wikimedia Commons)
But enough about getting it right, let’s talk about getting it wrong. Enter our antagonist.
Gyromitra will typically appear rufous, mahogany, or crimson - colors which are quite atypical for Morchella. Also, the cap appears wavy, folded, and cerebral in appearance, distinct from the craters and pits typical of morels.
It’s not hollow, So do not swallow! (Brian Adamo (adamo588), CC BY-SA 3.0, via Wikimedia Commons)
Cut one of these bad boys in half, and you will not find a hollow interior. You see the difference. But your patients might not. No one ever told them “if it’s wavy, don’t make gravy.” So, let’s talk tox.
Gyromitra exhibit their toxicity primarily via the toxin gyromitrin, which is hydrolyzed into monomethylhydrazine (MMH). If reading that made your eyes glaze over, you are obviously not a rocket scientist, as MMH is quite literally rocket fuel. It’s a badass little mushroom, especially when you eat it.
When you eat it, bad things happen, but not for a while. Most people feel pretty good for 5-10 hours. At first, they are satisfied that they fed themselves off the land. But then they feel very not good.
They start feeling a little nauseated, and their abdomen starts to cramp. Then the vomiting and diarrhea begins. Perhaps then they realize their mistake and come to your ED [1]. Perhaps they wait until the headache and ataxia begins. Perhaps they lay down and their roommate calls 911 when they begin having tonic-clonic seizures. Or maybe they are found comatose and nearly dead the following morning [2]. Let’s delve into the biochemistry to see what can save these patients from such a fate.
The Treatment
As we said, gyromitrin is hydrolyzed in the body into MMH. MMH itself reacts with pyridoxal phosphate (vitamin B6) to form hydrazone. While nobody seems to care much about hydrazone itself, we all know that things go wrong when you don’t have your vitamins. It turns out that vitamin B6 is a critical cofactor for the production of GABA, and when B6 is not available GABA production ceases. Less GABA means less inhibitory neurotransmission, and voila, seizures commence [3]!
A hefty dose of IV vitamin B6 treats and prevents seizures in cases of Gyromitra poisoning. Interestingly, this is the same reason why the international space station stockpiles vitamin B6 – to be able to treat cases of rocket fuel poisoning.
Sadly, the breakdown of MMH also leads to the production of oxidative chemicals and free radicals which are particularly destructive to the liver and red blood cells. These processes are not disrupted by B6 supplementation; methemoglobinemia, hemolysis and hepatic failure may ensue . While methemoglobinemia may respond to treatment with methylene blue, no current therapy prevents or treats hemolysis or hepatic failure from Gyromitra poisoning [4].
Mushrooms, rocket fuel, vitamins, blue lightning. Stay safe my friends.
Post by Jim Makinen, MD
Dr. Makinen is an attending physician of Emergency Medicine in Pittsburgh, PA and a member of the UC EM Class of 2021
Editing by Brandon Berger, MD
Dr. Berger is a PGY-4 in Emergency Medicine at the University of Cincinnati and soon to be Wilderness Medicine Fellow at MGH in Boston.
References
Noble H, Smith J. Poisoning due to raw Gyromitra esculenta (false morels) west of the Rockies. CJEM. 2007;9:127–30. doi.org/10.1017/S1481803500014937
Michelot D, Toth B. Poisoning by Gyromitra esculenta - a review. J Appl Toxicol. 1991 Aug;11(4):235-43. doi: 10.1002/jat.2550110403.
Goldfrank LR. Mushrooms. In: Flomenbaum NE, Howland MA, Goldfrank LR, Lewin NA, Hoffman RS, Nelson LS, editors. Goldfrank’s Toxicologic Emergencies. 8th ed. New York: McGraw-Hill; 2006. p. 1564–76.
Howland MA. Antidotes in Depth: Antituberculosis Medications. In: Flomenbaum NE, Howland MA, Goldfrank LR, Lewin NA, Hoffman RS, Nelson LS, editors. Goldfrank’s Toxicologic Emergencies. 8th ed. New York: McGraw-Hill; 2006. p. 861–75.
