Orellanine Mushroom Toxicity

Updated: May 11, 2023
  • Author: Reed Brozen, MD; Chief Editor: Sage W Wiener, MD  more...
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Practice Essentials

Cortinarius orellanus, the poznan cort mushroom, is one of the few types of mushrooms that can cause fatal poisonings. Of the thousands of mushroom species that are increasingly studied and collected by amateur mushroom hunters, about 100 can cause serious illness, but only about 10 cause death.

People become sick after ingesting mushrooms for several reasons. They may have ingested toxin-containing mushrooms or mushrooms that cause Antabuse-type reactions to alcohol; they may experience difficulty digesting large amounts of mushrooms or have immunologic reactions to mushroom-derived antigens.

Cortinarius species (corts) that may contain the orellanine toxin include the following:

  • C orellanus
  • C speciosissimus
  • C rainierensis
  • C callisteus
  • C gentilis (deadly cort; in Europe, gentle cort)
  • C splendens
  • C cinnamomeus group
  • C semisanguineus group

The most common of these in North America is probably C gentilis, although C orellanus and C speciosissimus are most often implicated in documented exposures. Presence of C orellanus in North America remains unconfirmed.

Orellanine is the major toxin found in these mushrooms. Orellanine (3,3',4,4'-tetrahydroxy-2,2'-bipyridine-1,1'-dioxide) is a colorless, crystalline, nephrotoxic compound. [1, 2]  Orelline is a possibly toxic product of orellanine.

Three other polypeptides have been identified: cortinarin A, cortinarin B, and cortinarin C. At least two of those appear to be nephrotoxic in experimental animals.

Mushroom identification is beyond the scope of this text, but the existence of corts is one of the many reasons not to eat little brown mushrooms (LBMs).



Patients with orellanine exposure may experience early symptoms because of other components of the mushroom; orellanine appears to be renal specific. Inhibition of alkaline phosphatase decreases production of adenosine triphosphate and disrupts cellular metabolism. Reaction is specific to the epithelium of cells in the proximal tubules and results in tubulointerstitial nephritis and acute kidney injury, with concomitant symptoms and complications. Orellanine seems to cause almost no reaction in glomeruli, although in an animal model, elimination of orellanine was almost exclusively by glomerular filtration. [3]

Studies of orellanine poisoning in rats have shown no signs of acute toxicity apart from kidney injury, but a study of orellanine poisoning in mice showed tubular necrosis as well as effects on other organs, as follows [4] :

  • Liver injury, demonstrated by reduced liver weight, elevated liver enzymes, and histopathology characterized by mild hepatocellular vacuolation
  • Splenic atrophy, characterized by lymphocytolysis
  • Thrombocytopenia.

However, a study of 28 patients with orellanine poisoning noted that no signs of acute damage were present in any other organ except the kidney. [5]



In 2021, 9 exposures of orellanine-containing mushrooms were reported to the American Association of Poison Control Centers' (AAPCC) Toxic Exposure Surveillance System. [6]  A range of 0-9 exposures per year have been reported over the past 14 years. The reports by year can be found at the APPC site.

Unknown mushroom type makes up most mushroom exposures each year, usually accounting for over 70% of mushroom exposures (eg, 4887 in 2021). However, deaths in this group remain remarkably low (0-2 per year since 1996). [6]

A study published in May 2000 that used data from the National Center for Health Statistics found no difference when compared with AAPCC data in numbers of deaths caused by mushroom exposures. [7]

No accurate global database exists, but mushroom gathering is more common in Eastern and Western Europe than in North America. Most documented cases of orellanine toxicity are from Europe.

Mushroom poisoning is the leading cause of foodborne disease outbreaks and foodborne-related deaths in China. The Chinese Foodborne Disease Outbreak Surveillance System reported a total of 10,036 mushroom poisoning outbreaks in 2010-2020. These outbreaks resulted in a cumulative 38,676 illnesses and 788 deaths during that period. In 2020, 2075 mushroom outbreaks were reported. [8] Three outbreaks and no deaths were attributed to Cortinarius species, but over 60% of the outbreaks involved unidentified mushrooms. [9] The majority of the outbreaks (84.6%) were associated with consumption in the home and were related to self-harvesting of wild mushrooms. [8, 9]



A short latent period before onset of illness and kidney injury portends more severe renal insult and prolonged period of renal failure than delayed onset of illness. Relatively mild degrees of kidney insufficiency may resolve within weeks to months. Some patients may be treated expectantly without need for hemodialysis. In more severe cases, kidney failure can persist months to years requiring chronic hemodialysis or kidney transplantation. [5]

Few data are available to estimate incidence of orellanine poisoning. Most reported cases of kidney failure are from Europe. The AAPCC last reported a recognized Cortinarius exposure with a major effect in outcome (ie, exposure resulted in life-threatening signs or symptoms or resulted in significant residual disability) in 1999. Since 1999 no outcomes have occurred in the major category and only 3 total in the moderate class (ie, signs or symptoms more pronounced, more prolonged, or more systemic in nature than minor symptoms usually indicating the need for some form of treatment, but the patient had no residual disability). [6]