Klippel-Feil (KF) syndrome is a rare condition that causes some of the bones in the neck to fuse before birth. Many people with the condition have a typical life expectancy, but it can sometimes lead to complications, such as compression of the spinal cord.

Klippel-Feil syndrome in neck shown in a photo collage.Share on Pinterest
Design by Medical News Today, photograph Sonkaya AR, Kaya E, Firtina S, Mehmet AK, CC BY 3.0, via Wikimedia Commons

KF syndrome occurs when the bones that make up the upper spine — the cervical spine — do not divide and separate the way they should during pregnancy. Important neurologic and vascular structures interact with the cervical spine. Treatment cannot cure the condition but can stabilize the spine and relieve symptoms.

Read on to learn more about KF syndrome, its symptoms, causes, and treatments.

KF syndrome causes two or more bones in the neck to remain fused instead of separating into distinct bones. It occurs during the early stages of fetal development.

Health experts may refer to the condition using one of several other names, which include:

  • cervical fusion syndrome
  • cervical vertebral fusion
  • cervical vertebral fusion syndrome
  • congenital dystrophia brevicollis
  • dystrophia brevicollis congenita
  • fusion of cervical vertebrae
  • Klippel-Feil sequence
  • vertebral cervical fusion syndrome

Estimates suggest that KF syndrome affects one in 40,000 newborns worldwide.

The life expectancy for a person with KF syndrome is the same as it is for someone in the general population, as long as they receive prompt diagnosis and treatment.

However, due to the shape of the vertebrae in KF syndrome, people with the condition have an increased risk of neurological problems. Therefore, people should attend regular checkups with their doctor so they can monitor for signs of this.

Symptoms of KF syndrome begin to show between birth and around 2 years of age. People with the condition commonly have:

  • a shorter neck
  • a low hairline at the back of their head
  • difficulty moving the top of their spine

The fused cervical vertebrae can also cause:

  • nerve pain or damage in the head, neck, or back
  • joint pain
  • hearing impairment
  • differences in the development of the:
    • head and face
    • muscles
    • sex organs
    • brain and spinal cord
    • arms and legs
    • fingers

A person with KF syndrome may also have other conditions, such as:

  • scoliosis, or curvature of the spine
  • spina bifida, a condition where the bones in the vertebral column do not fully cover the spinal cord
  • cleft palate
  • breathing problems
  • heart conditions

Doctors do not know what causes KF syndrome in most cases. However, some people have a variant in one copy of the GDF6 or GDF3 genes. These genes influence bone development and the division of the spine into individual bones.

Others may have a variant in both copies of the MEOX1 gene, which also plays a role in forming body structures in the early stages of fetal development.

For some people, KF syndrome is a feature of another condition. These health issues may include Wildervanck syndrome, which also affects the bones of the neck, eyes, and ears, or hemifacial microsomia, where half of one side of the face does not grow as it should.

In these cases, a person inherits KF syndrome along with this condition.

Some researchers have suggested a link between KF syndrome and problems with blood flow to the fetus, as well as neural tube abnormalities, which form the brain and spine of the fetus early in pregnancy.

Doctors may diagnose a newborn with KF syndrome following a thorough physical examination and specialized tests. For instance, an MRI scan can show doctors:

  • the spaces between the vertebrae
  • the degree to which the vertebrae have joined together
  • whether the vertebrae are compressing the spinal cord

Other imaging tools to help doctors diagnose KF syndrome include CT scans and X-rays.

If a doctor is concerned that a person also has hearing, heart, kidney, or eye conditions, they may order further specialized tests to check for these problems.

If a person has only mild symptoms of KF syndrome, or the symptoms do not become apparent until later in life, they may not receive a diagnosis for years.

Doctors provide treatment for KF syndrome according to a person’s individual symptoms. For some people, this might include surgery to:

  • make the neck, or head and neck, more stable
  • relieve pressure on the spinal cord
  • reduce curving of the spine

Other therapies that may help relieve a person’s symptoms include:

  • physical therapy
  • collars or braces for the neck
  • traction, a treatment that involves lightly pulling on the head to create space between the cervical vertebrae
  • nonsteroidal anti-inflammatory drugs
  • other pain medications
  • hearing aids, if a person has a hearing impairment

Currently, there is no cure for KF syndrome.

Most people with KF syndrome can expect positive outcomes if they receive prompt treatment. However, doctors may recommend avoiding activities that might cause a neck injury.

If the fused part of the person’s spine is below vertebrae C3 — the bone third from the top — they can play contact sports. If the fused part is above vertebrae C3, they should avoid contact sports due to having a heightened risk for spinal injury.

KF syndrome occurs when two or more bones in the spine and neck do not separate into distinct vertebrae during fetal development. This can lead to a range of possible symptoms, including joint pain, hearing impairment, and changes in facial structure.

Around one in 40,000 infants develop KF syndrome before birth. People with the condition may have alterations in the GDF3, GDF6, or MEOX1 gene, which affect growth. There is no cure, but surgery and other therapies may help relieve a person’s symptoms.