Orellanine

Orellanine is a potent nephrotoxin produced by several Cortinarius mushrooms, most notably Cortinarius orellanus (fool's webcap) and Cortinarius rubellus (deadly webcap). In humans, ingestion can lead to delayed-onset acute kidney injury, sometimes with lasting renal damage.

Toxicology and mechanism are not fully understood. Orellanine is taken up by renal proximal tubular cells and is thought to induce oxidative stress and disrupt cellular energy production, leading to tubular necrosis. The toxin is relatively stable and cooking does not reliably destroy it, contributing to its danger when misidentified mushrooms are consumed.

Clinical presentation typically includes a latent period of about 3 to 14 days after ingestion. Early symptoms, such as nausea or abdominal discomfort, may be non-specific. Renal symptoms then predominate, with reduced urine output, edema, electrolyte disturbances, and a rising serum creatinine and BUN. The course can progress to significant kidney injury requiring renal replacement therapy, such as dialysis, in severe cases.

Diagnosis relies on a history of ingestion of a Cortinarius-containing mushroom and laboratory evidence of acute kidney injury. Identification of the specific mushroom can support the diagnosis, but routine clinical tests for orellanine are not widely available.

Treatment is supportive, as there is no specific antidote. Management includes careful fluid balance, electrolyte management, and renal replacement therapy as indicated. Prognosis varies; some patients recover renal function over weeks to months, while others sustain long-term or permanent impairment.

Prevention centers on avoiding consumption of wild Cortinarius species and educating foragers about the risks associated with these mushrooms.