Mushrooms containing amatoxins generate the highest number of fatal mycete poisonings on the planet. These toxins are produced not only by Amanita species, such as the well-known Amanita phalloides, but also by other genera, including Lepiota. In this work we report the treatment of a 51-year-old male patient weighing 79 kg who was referred to the hospital after 36 h of ingesting mushrooms. The mushrooms were identified as Lepiota brunneoincarnata, found for the first time in Argentina. The patient presented general malaise, nausea and repeated vomiting, abdominal pain, and diarrhea. Thanks to a quick anamnesis and early and accurate identification of the fungus, he was administered a nasogastric tube and serial activated charcoal. Additionally, N-acetylcysteine, phytomenadione and penicillin G EV were administered. The patient was discharged 11 days after admission. This case highlights the importance of obtaining a correct and sufficient anamnesis on fungi, enabling rapid analysis of them, and initiation of timely treatment for intoxication. Once again, the importance of having Toxicological Information and Advice Centers (CIAT) with experience and knowledge of micetisms is demonstrated.