Paxillus involutus — Poison pax, brown roll-rim

Poison pax

Poison pax2, photograph by Ludovic Le Renard.

Poison pax

Poison pax13 young, unbruised specimens, photograph by David Carmean.

Poisonous


Gills: Decurrent, pale yellow to red-brown
Spore print: Brown


Odour: Indistinct
Cap: 5–10 (–20) cm in diameter. When young, convex with deeply inrolled margin. Expands and becomes flatter with age, the centre commonly becoming depressed, sometimes with a central umbo while the margin remains inrolled. The surface is a slightly greenish brown, becoming brown with age. The inrolled edge may be distinctly grooved or striate.
Gills: Rather crowded, thick, pale yellow then brown, rapidly bruising red-brown when touched. The gills are easily peeled off from the underside of the cap.
Stem: 3–7 (–12) cm long x 1–3 (–4) cm wide and in many cases shorter than the cap is wide, with solid flesh. The colour is similar to that of the cap, and the stem also bruises easily.
Ring or veil: None.
Cup: None.
Spores: ~7–9 x 5–6 µm, brown.
Habitat: In various forest types, with coniferous and deciduous trees. Ectomycorrhizal
Geographical range: The name Paxillus involutus has been used for at least three different Paxillus species of western North America4. As a result of the taxonomic confusion, the range extent and habitat of each individual species is unclear. The poison pax, Paxillus involutus, is widespread in temperate and boreal Europe and barcode sequencing shows that it occurs in BC.

Paxillus cuprinus, the coppery pax, is common in parks and lawns growing with planted birch (Betula) from California to BC. Two other species grow in natural habitats, but their names and identities have yet to be sorted out. They differ in subtle macroscopic and microscopic characters from each other. All Paxillus species are considered toxic.

Coppery pax

Coppery pax, Paxillus cuprinus14, photograph by Ludovic Le Renard.

Poisonings by Paxillus species are due to the formation of antibodies against the mushrooms. Severe hemolysis and renal failure, followed by death, may occur. The severe symptoms might happen the first time these mushrooms are eaten, or after the nth time, when the threshold of antibodies is reached. Paxillus species also accumulate mercury from the soil10.

Symptoms: Cardiovascular collapse and severe stomach aches, nausea and vomiting develop a few hours after having eaten the mushrooms.
 

Treatment: Contact your regional Poison Control Centre if you realize you or someone you know may have been poisoned by the poison pax or its relatives. Poison centres provide free, expert medical advice 24 hours a day, seven days a week. If possible, save the mushrooms or some of the leftover food containing the mushrooms to help confirm identification.
 

Poison Control:
British Columbia: 604-682-5050 or 1-800-567-8911.
United States (WA, OR, ID): 1-800-222-1222.

Cases: In Washington and Oregon, one person experienced kidney failure and two had muscle spasms and vomiting as a result of eating poison pax mushrooms11. In BC, a couple ate poison pax, became ill, and then a few days later, one of the two required hospitalization after again barbecuing and eating a large quantity (>12) of the mushrooms in Brandywine Falls Provincial Park12.

1
UBC. University of British Columbia Herbarium Database, <http://bridge.botany.ubc.ca/herbarium/database.php> accessed February 1, 2018.
2
Specimen Paxillus involutus UBC F33239, GenBank #MG953978.
3
Trudell, S. & Ammirati, J. F. Mushrooms of the Pacific Northwest. Timber Press, Portland, Oregon (2009).
4
Siegel, N. & Schwarz, C. Mushrooms of the Redwood Coast. A Comprehensive Guide to the Fungi of Coastal Northern California. Ten Speed Press, Berkeley, California (2016).
5
Jargeat, P., Chaumeton, J. P., Navaud, O., Vizzini, A. & Gryta, H. The Paxillus involutus (Boletales, Paxillaceae) complex in Europe: Genetic diversity and morphological description of the new species Paxillus cuprinus, typification of P. involutus s.s., and synthesis of species boundaries. Fungal Biology 118, 12-31, doi:10.1016/j.funbio.2013.10.008 (2014).
6
Flammer, R. Paxillus syndrome: immunohemolysis following repeated mushroom ingestion. Schweizerische Rundschau für Medizin Praxis 74, 997–999 (1985).
7
Bschor, F., Kohlmeyer, J. & Mallach, H. J. Neue Vergiftungsfälle durch Paxillus involutus. Zeitschrift für Pilzkunde 29, 1–3 (1963).
8
Winkelmann, M., Stangel, W., Schedel, I. & Grabensee, B. Severe hemolysis caused by antibodies against the mushroom Paxillus involutus and its therapy by plasma-exchange. Klinische Wochenschrift 64, 935-938, doi:10.1007/bf01728620 (1986).
9
Winkelmann, M., Borchard, F., Stangel, W. & Grabensee, B. Tödlich verlaufene immnunhämolytische Anämie nach Genuß des Kahlen Kremplings (Paxillus involutus). Dtsch med Wochenschr 107, 1190-1194, doi:10.1055/s-2008-1070100 (1982).
10
Falandysz, J. & Brzostowski, A. Mercury and its bioconcentration factors in Poison Pax (Paxillus involutus) from various sites in Poland. Journal of Environmental Science and Health Part a-Toxic/Hazardous Substances & Environmental Engineering 42, 1095-1100, doi:10.1080/1093452071418599 (2007).
11
Beug, M. W., Shaw, M. & Cochran, K. W. Thirty-plus years of mushroom poisoning: Summary of the approximately 2,000 reports in the NAMA case registry. McIlvainea 16, 47-68 (2006).
12
UBC. Paxillus involutus UBC Herbarium Database F13305 <http://bridge.botany.ubc.ca/herbarium/database.php> accessed April 30 2018.
13
Paxillus involutus mb20181020.3 UBC F3XXXX.
14
Specimen Paxillus cuprinus UBC F33267, GenBank #MH718247.