What Is Fatal Familial Insomnia?

Medically Reviewed by Christopher Melinosky, MD on March 07, 2024
3 min read

Fatal familial insomnia (FFI) is a rare genetic condition that causes progressively worsening insomnia — an inability to sleep. The insomnia worsens to the point that it severely impacts daily functioning, eventually causing coma and then death.

If you have trouble sleeping, it's highly unlikely that you have FFI. Experts estimate that only 100 people in 30 families across Europe, China, Japan, Australia, and the U.S. are carriers of the gene that causes this disease.

There’s a non-genetic version of this disease called sporadic fatal insomnia (sFI). Experts don’t know what causes sFI.

FFI isn’t actually a sleep disorder, even though it contains the word insomnia. FFI is a prion disease, which means it’s caused by a malfunction of proteins in the brain. Some prion diseases are genetic — like FFI — while others are caused by infections.

A mutation to the PRPN gene causes the prion malfunction in people with FFI. Most of the time, this mutation is passed down from a parent. However, in rare cases, the gene spontaneously mutates. This mutation occurs in the egg or sperm that forms the baby.

The PRPN gene controls the creation of the PrP protein. Experts aren’t sure exactly what this protein does, but when you have this specific genetic mutation, the protein forms in the incorrect shape. This makes it toxic to your body. The malformed protein builds up in your thalamus over your lifetime, damaging it.

Your thalamus typically controls how you sleep and eat. It also helps regulate your body temperature. The damage that occurs over time affects these processes in people with FFI.

The PRPN mutation that causes FFI is an autosomal dominant mutation. That means that you only need to receive one copy of this gene to get the disease.

If you have this genetic mutation, you have a 50% chance of passing on the disease to your child with each pregnancy.

Symptoms of FFI usually appear when you’re between ages 40 and 60. They start off mild but progress quickly.

The first symptom most people experience is insomnia, or difficulty sleeping. This may come with confusion and trouble focusing. The insomnia worsens over time, and other symptoms may start to appear. These include:

As the disease progresses further, other fatal familial insomnia symptoms include:

Many of the symptoms that happen after insomnia begins are caused by a lack of sleep.

Most people with FFI die within 6 months to 36 months of the onset of symptoms from heart problems or infections caused by the underlying condition.

The symptoms of sporadic fatal insomnia are similar but have a different progression. If you have sFI, you may first experience issues with balance or memory. 

Your doctor will perform a series of tests to determine if you have FFI.

They’ll likely start with a physical exam and take your family history. They may do genetic testing, spinal fluid testing, or a sleep study.

When a person dies undiagnosed, an autopsy can confirm FFI.

Fatal familial insomnia treatment focuses on managing symptoms. There’s currently no cure.

Because FFI is so rare, there’s no standard protocol for how to manage the symptoms. You’ll work with a team that usually includes a neurologist, psychiatrist, social worker, and other health professionals to address your specific symptoms.

Treatments include:

  • Taking vitamins and supplements
  • Eating a balanced diet
  • Stopping or changing medications that make symptoms worse
  • Using sedatives, antipsychotics, or melatonin to help with sleeping
  • Seeing a therapist

To prevent future cases of FFI, your doctor may recommend genetic testing for your entire family. Because this disease comes on in middle age, without genetic testing, your family members could pass it on before they know they have the PRPN gene mutation.

While your insomnia isn’t likely to be FFI unless you have a family history, see your doctor if you’re having trouble sleeping, or are having confusion or problems controlling your movements. These symptoms may be signs of other conditions.