On Apr. 29, 2024, Oregon Health Sciences University (OHSU) reported a patient with the first documented case of illicit fentanyl inhalation causing toxic leukoencephalopathy, where large sections of white matter in his brain became inflamed to the point that he had lost consciousness and risked irreversible loss of brain function, or possibly death. In the case report, published online in the journal BMJ Case Reports, clinicians laid out the surprising and unprecedented diagnosis: toxic leukoencephalopathy by fentanyl inhalation.

the 47-year-old arrived by ambulance to the emergency department at Oregon Health & Science University on Feb. 25, 2023. He was found collapsed in his hotel room, where he was staying during a business trip. Medical experts had documented previous cases caused by inhaling heroin, but the OHSU patient is believed to be the first documented case involving inhalation of illicit fentanyl.