Cortinarius species
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A very large genus of brown mushrooms, two members of which cause irreversible kidney destruction weeks later. All have a cortina, a cobwebby partial veil, and a rusty spore print. The genus is a good reason to treat 'small brown mushroom with a rusty print' as a hard stop.
If you may have eaten this: get to an emergency department now and say you may have eaten an amatoxin-containing mushroom. Don’t wait for symptoms, the symptom-free window is part of the poisoning, not a sign you’re fine. Bring a sample if you can. Treatment works far better before liver damage sets in.
What it does
- Toxin
- Orellanine, in C. rubellus and C. orellanus. It destroys the kidneys rather than the liver, and there is no antidote.
- Time to symptoms
- The longest delay of any mushroom poisoning: 2 days to 3 weeks before symptoms. Thirst, then declining urine output, then kidney failure.
- Outcome
- Permanent kidney failure requiring dialysis or transplant. The delay is so long that people rarely connect the illness to the meal.
Decisive characters
Each of these settles the question on its own. If one says no, the answer is no, regardless of what everything else says.
Supporting characters
Useful corroboration. Not sufficient alone.