Undercooked Yunnan mushroom linked to tiny-people hallucinations, new study finds

Lanmaoa asiatica in Yunnan markets sends diners into hallucinations of tiny people, plus nausea, vomiting, and other neuropsychiatric symptoms, when it is eaten undercooked. A retrospective review at the First People’s Hospital of Yunnan Province tracked 81 poisoning patients admitted from January 2023 through December 2023, and the cases clustered in midsummer.

Patients were 14 to 84 years old, with a median age of 42.5, and 72.8% were female. July was the danger month, with 55 cases, or 67.9% of the total. The most common presentation was mixed neuropsychiatric and gastroenteritic symptoms, seen in 64.2% of patients, while visual hallucination was the most common first symptom at 69.1%. No fatalities were reported, and the median hospital stay was 3 days.

Lilliputian hallucinations are the perception of pint-sized figures that patients often describe as elf-like people moving across furniture, crawling, or marching through the room. The mushroom, locally called Jian shou qing, is sold in markets, served in homes and restaurants, and eaten during the June-to-August mushroom season in Yunnan, where local diners warn one another to cook it thoroughly before eating.

University of Utah mycologists Colin Domnauer and Bryn Dentinger sequenced 53 mushroom samples across the broader Lanmaoa genus and searched for genes tied to psilocybin and ibotenic acid. They found no close genetic matches to those known psychedelic pathways, pointing to a different, as-yet-unidentified metabolite.

Lanmaoa asiatica is the type species of Lanmaoa, a genus established in 2015, and NCBI lists the current accepted name as Lanmaoa asiatica G. Wu & Zhu L. Yang, 2015. University of Utah researchers put the figure at hundreds of these cases every year, and earlier literature, including a 1991 Chinese Academy of Sciences paper, had already flagged similar hallucinations in the region.