Fatal Familial Insomnia (FFI) is a genetic sleep disorder - but it is a rare one. It has been diagnosed in less than 40 families worldwide, including the Chicago music teacher, Michael Corke, who featured in the BBC documentary The Man Who Never Slept. 

FFI begins as an unexplained sleeplessness during middle age and rapidly develops into a fatal insomnia and it’s caused by a genetic mutation.

Fatal insomnia is a baffling condition (and only officially discovered 10 years ago) because its symptoms resemble many common diseases - like dementia, end-stage alcoholism and encephalitis. The main symptom of FFI is the inability to sleep, and this causes high pulse and blood pressure, excessive sweating and a loss of coordination and motor skills. The disease manifests itself in four deteriorating stages: 

STAGE ONE - The sudden and inexplicable onset of insomnia causes panic attacks and unfounded phobias, lasting for about four months.

STAGE TWO - As sleep deprivation takes hold, the panic attacks and hallucinations become severe, lasting for a further five months.

STAGE THREE - The total insomnia causes rapid weight loss and limited mental functioning, lasting for up to three months.

STAGE FOUR - Finally, the patient suffers from dementia and unresponsiveness, lasting for up to six months.

Eventually the patient falls into a coma and dies from total insomnia. One of the most tragic aspects of FFI is that though the sufferer shows signs of dementia, they have a clear understanding of what is happening to them, while enduring the physical agony of total sleeplessness.

Fortunately, a diagnostic test is now available, but there is no known cure for FFI. The only hope is that gene therapy will offer a solution to future generations.