These terrifying images are what it's like to have extraordinarily rare condition 'demon face syndrome'

Long misdiagnosed as schizophrenia, the details of what a patient actually sees while enduring 'demon face syndrome,' or prosopometamorphopsia (PMO), has long remained a mystery — until now.

Only about 75 cases have ever been documented of the syndrome, in which a person perceives unusual, often grotesque distortions when staring at a human face.

But a rare individual with the condition, a 58-year-old male who reached out to neuropsychologists at Dartmouth, has the unique ability to see faces normally on paper and on screens, despite seeing more eerie 'demon faces' in his real life.   

This split allowed him and the researchers to reliably illustrate, for the first time, what faces can look like for a person living with the haunting vision of PMO. 

'Most of the articles about PMO have been brief case reports about individual cases,' Dartmouth Professor Brad Duchaine told DailyMail.com, 'written by the neurologists who happened to encounter them in their clinical practice.'

'Our report is especially interesting,' he said, 'because [...] we can be confident that the distortions of his visualizations accurately reflect what he experiences.'

A rare individual with a variation of the 'demon face syndrome' has the unique ability to see faces normally on paper and on screens, despite seeing more eerie 'demon faces' in his real life. The divide allowed researchers to properly illustrate, for the first time, what faces look like to a person living with the demon-tinted glasses of prosopometamorphopsia (PMO) 

Damage that led to PMO was often found in the form of lesions on the occipital and temporal lobes in the back of the brain, near areas that neuroscientists have classified as face-recognizing areas, marked in green above. But some mysterious cases are harder to trace

'It's not uncommon for people who have PMO to not tell others about their problem with face perception,' Duchaine, a coauthor on the new study, said in a statement. 

'They fear others will think the distortions are a sign of a psychiatric disorder,' he added. 'It's a problem that people often don't understand.'

Duchaine and Dartmouth PhD student Antônio Mellon ran their 58-year-old PMO patient through a series of tests not unlike modern 'police sketch artists.'

The researchers, who work with Dartmouth's Social Perception Lab, first took a photograph of a volunteer participant's face. 

They then showed their case study patient that photo on a computer screen, asking him to stare at the real face of that same participant and give them feedback on the differences he perceived.  

'The distortions he perceives,' Prof. Brad Duchaine (above) told DailyMail.com, 'provide a nice illustration that we do not have access to the world. Instead, all of our experiences are constructed by the brain'

Using that real-time feedback from their 58-year-old, Mellon and Duchaine used computer software to adjust the photograph of the volunteer participant to match how his PMO condition was altering the faces that he was seeing.

Their results, published today in medical journal The Lancet, look almost goblin-like — faces with pointy ears; sharp noses; and wide, reptilian mouths. 

'The distortions he perceives,' Duchaine told DailyMail.com via email, 'provide a nice illustration that we do not have access to the world. Instead, all of our experiences are constructed by the brain.'

While the study is a breakthrough in understanding how this one person with PMO sees the world, a broad understanding of the condition is only beginning to emerge. 

The visual distortions classified as PMO can vary widely. 

One 52-year-old woman, according to a previous study in The Lancet, suffered all her life seeing human faces morph into dragon-like visages. In another case, a 44-year-old woman described seeing faces that 'look almost like a caricature.'

'Distortions in the great majority of the PMO cases in the literature began after an obvious neurological event and nearly all of those who were scanned had brain damage in visual regions of the brain,' Duchaine told DailyMail.com.

The damage was often found in the form of lesions on the occipital and temporal lobes, near areas that neuroscientists have classified as face-recognizing areas.

But, as his Social Perception Lab has continued to search for new manifestations of the syndrome — with an open call for new applicants on their dedicated web page — the lab is starting to learn of still more mysterious cases.

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'We are hearing through our website from many people who are unaware of a neurological event that coincided with the onset of their distortions,' he said. 

'We have also heard from a handful of people who report having distortions their entire lives and even two cases with family members who have also experienced face distortions.'

Psychologists and other clinicians have been aware of the condition since at least 1953, when a sympathetic neurologist first coined its unwieldy official name, 'prosopometamorphopsia.'

'MacDonald Critchley, one of the giants of 20th-century UK neurology, coined the term,' according to Duchaine. 

'Interestingly, Critchley was himself prosopagnosic — he had great difficulty recognizing facial identity.' 

The name is derived from the Greek word for face, 'prosopon,' and a preexisting medical term for perceptual or vision-based distortions 'metamorphopsia.'

The variance in symptoms includes not only shapes and sizes, but colors and even positions of facial features.

Taken along with the documented fact that PMO can arrive suddenly, lasting for just days, or for many years, or in some cases arriving at birth as a lifelong issue, Duchaine noted that mental health professionals have often struggled to correctly identify it.

'We've heard from multiple people with PMO that they have been diagnosed by psychiatrists as having schizophrenia and put on anti-psychotics,' Duchaine said, 'when their condition is a problem with the visual system.'