Talk about a nightmare condition.

Struggling to sleep is a common issue, with nearly 1 in 5 adults tossing and turning all night long.

But trouble sleeping may be the least of your worries if you’re dealing with fatal familial insomnia (FFI), a rare and incurable, deadly genetic condition.

While insomnia can be caused by several triggers, including what you eat before bedtime, it’s just one sign of FFI.

A rare condition that affects the brain and nervous system, FFI can lead to trouble sleeping, muscle twitching and memory loss or dementia.

And the symptoms get worse over time.

Other signs can include high blood pressure, anxiety, faster-than-normal heart rate and hallucinations.

While many early symptoms can resemble Alzheimer’s disease or dementia, you should talk to your doctor if you’re experiencing memory loss and loss of motor skills combined with difficulty sleeping.

These symptoms can begin between the ages of 20 and 70, with an average onset age of 40.

The condition is inherited from a mutated PRNP gene passed down by biological parents, and while extremely rare, it can occur in people without a family history.

The PRNP gene that exists in the brain is responsible for making the prion protein PrPC, which regulates several bodily functions, including sleep.

When the PRNP gene is changed, the PrPC proteins can’t be built correctly, accumulating in the brain and becoming toxic to nervous system cells.

The disruption to sleep caused by FFI can lead to a vicious cycle of deteriorating health, as sleep is crucial to physical and mental health.

As the condition worsens over time, life expectancy is poor after symptoms start, ranging from a few months to a couple of years.

While there’s no cure for FFI, symptoms can be managed or medications may provide temporary relief.

Treatments include medications like gamma-hydroxybutyrate or phenothiazines to induce deep sleep, clonazepam for muscle spasms, vitamins like B12 or iron, psychosocial therapy and potentially hospice care.

However, other medications and supplements that are used for sleep — such as melatonin or sedatives like barbiturates or benzodiazepines — are ineffective for managing FFI symptoms.

New treatment options are currently being researched, including the use of the antibiotic doxycycline to prolong lifespan in those with fatal familial insomnia.