The case of a Belgian woman who believed that she was a chicken has been cited by psychiatrists as an example of a potentially under-reported mental health disorder linked to depression.
The 54-year-old woman, who had no history of drug or alcohol abuse, was found by her brother in her garden clucking and blowing her cheeks before crowing like a rooster.
On arrival at an accident and emergency ward, the woman had expressed her conviction and had spoken of feeling new sensations in her limbs.
Following a seizure, the thoughts no longer plagued the woman and she was said to be embarrassed by the episode, of which her memory was impaired.
There have been only 56 case descriptions in medical and historical literature in the period between 1850 to 2012.
Patients have reported believing they are a dog, lion, tiger, hyena, shark, crocodile, frog, bovine, cat, goose, rhinoceros, rabbit, horse, snake, bird, wild boar, gerbil and a bee.
The woman cited by the researchers had been in a relationship for two decades and had a stable job in a pharmacy where she returned to work a year later.