A 78-year-old man in France 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, doctors said.

According to a report of the man's case published in the journal Neurocase, the man said he noticed a stranger in his house who stayed in the bathroom mirror.

"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," researchers said in the report.

The man, identified in the report as Mr B, talked to the stranger but eventually told his daughter that he had become aggressive.

The daughter drove him to the hospital where he was diagnosed with a condition called atypical Capgras syndrome.

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, said in a regular case of Capgras syndrome, 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'.

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.

Doctors believe that people with atypical Capgras may have impairments in two different brain pathways