A man who thought he saw a "stranger" in the bathroom mirror, when he was actually looking at his own reflection, turned out to have a rare neurological condition, a new case report finds.
The 78-year-old man in France, identified in the report as Mr. B, noticed a stranger in his house. Mr. B said that the stranger looked just him, but stayed in the bathroom mirror, according to the authors of the report published online Aug. 25 in the journal Neurocase.
"The stranger was a double of himself: he was the same size, had the same hair, body shape, and features, wore the same clothes and acted the same way," the researchers wrote in the report. "Mr. B. talked with this stranger and was puzzled because he knew much about him. Mr. B. even brought food to the mirror with cutlery for two persons." [Senses and Non-Sense: 7 Odd Hallucinations]
"Eventually, the patient told his daughter that the stranger [had] became aggressive, and she decided to drive her father to the hospital," said Dr. Capucine Diard-Detoeuf, a neurologist at the University Hospital of Tours in France, who treated the man and is one of the co-authors of the report.
After a checkup, doctors diagnosed Mr. B with a condition called atypical Capgras syndrome. In a regular case of Capgras syndrome (named after French psychiatrist Joseph Capgras, who first published a report on the disorder in 1923), a person thinks that a friend or family member has been replaced with an identical imposter.
Mr. B's case was atypical because his delusion did concern another person, but himself, Diard-Detoeuf told Live Science in an email.
Doctors prescribed Mr. B an antipsychotic medication for his delusions. They also gave him anti-anxiety medication because he felt anxious and nervous about living with an "aggressive stranger" in his home, Diard-Detoeuf said.
After taking the medications for three months, Mr. B recovered, and reported that the stranger had disappeared.
Man in the mirror
Two similar cases of Capgras have been reported in the literature. According to a 1968 report, a 61-year-old woman in New Zealand became frightened by a double of herself who only appeared when she looked into the mirror, the authors said.
The other case involved a 77-year-old woman. That woman actually imagined that she talked with her "double" in the mirror — a woman just so happened to be identical to her in appearance, age, background and education, according to a 1989 case report.
It's not clear why people develop Capgras syndrome, but one idea is that it's similar to a condition called prosopagnosia, in which people become unable to recognize familiar people's faces. (Prosopagnosia is also known as face blindness, and has been diagnosed in people such as the late neurologist Oliver Sacks and primatologist Jane Goodall.)
But the authors of the new case report, who are all neurologists and psychiatrists at the University Hospital of Tours, said that atypical Capgras is likely more complicated. They speculated in their report that people with the condition have impairments in two different brain pathways, not just one.
People with face blindness might not be able to recognize familiar faces, but tests of their skin conductance, which reveal the body's physiological reaction to a stimulus, show that they still react to these faces emotionally. It is likely that people with face blindness, the "overt," or direct pathway, that sustains face recognition is impaired, Diard-Detoeuf said.
In contrast, patients with regular Capgras syndrome can identify familiar faces, but don't show any emotional reaction to them in skin conductance tests, Diard-Detoeuf said. It's likely people with regular Capgras have brain damage to a different pathway, called the covert pathway, which sustains familiarity. If they see a familiar face but don't feel a sense of familiarity, a subsequent feeling of strangeness will ensue, Diard-Detoeuf said. [10 Things You Didn't Know About the Brain]
However, Mr. B and the other patients who didn't recognize themselves likely had problems with both their covert and overt pathways, the authors said.
"The case reports describe a very rare and fascinating condition, where the patient recognized himself [or herself] as a stranger," said Dr. Paul Wright, the chairman of neurology at North Shore University Hospital and Long Island Jewish Medical Center in New York, who was not involved with the report.
Even though the syndrome appears similar to face blindness, the study's authors urged doctors to be careful not to misdiagnose it.
"This clinical condition could be interpreted as an atypical Capgras syndrome… and should be distinguished from prosopagnosia," Diard-Detoeuf said.
People with any condition that falls into the category researchers call "misidentification syndromes," such as atypical and typical Capgras, may be helped by taking antipsychotic medications, although more research is needed to know for sure, he said.
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Laura is the archaeology and Life's Little Mysteries editor at Live Science. She also reports on general science, including paleontology. Her work has appeared in The New York Times, Scholastic, Popular Science and Spectrum, a site on autism research. She has won multiple awards from the Society of Professional Journalists and the Washington Newspaper Publishers Association for her reporting at a weekly newspaper near Seattle. Laura holds a bachelor's degree in English literature and psychology from Washington University in St. Louis and a master's degree in science writing from NYU.