Thanatophoric Dysplasia

What is thanatophoric dysplasia?

Thanatophoric dysplasia is a genetic condition that affects the development of a fetus’ bones and lungs.

The term “thanatophoric” is ancient Greek for “death bearing.” This is because many children are stillborn or die during or shortly after birth due to breathing problems/respiratory failure because of lung underdevelopment before birth.

Rarely, a child with this condition may survive into childhood with extensive treatment to address respiratory failure. Respiratory failure happens when there’s not enough oxygen or too much carbon dioxide in your child’s body.

What are the types of thanatophoric dysplasia?

There are two types of thanatophoric dysplasia characterized by how bones form:

• Type 1: Babies born with type 1 have very short limbs, a narrow chest, curved thigh bones and a flat spine (platyspondyly) and, rarely, craniosynostosis (skull bones close too soon). Thanatophoric dysplasia type 1 is more common than type 2.
• Type 2: Babies born with type 2 have very short limbs, a narrow chest, straight thigh bones and joints in the skull that close too soon and cause bulges at the front and sides of their head (cloverleaf skull).

How common is thanatophoric dysplasia?

Thanatophoric dysplasia is rare and occurs in an estimated 1 out of every 20,000 births.

What are the signs and symptoms of thanatophoric dysplasia?

Thanatophoric dysplasia affects how a fetus’ lungs, bones and joints grow and develop in the uterus. This can lead to signs that include:

• Underdeveloped lungs due to short ribs and a narrow chest that keeps lungs from growing fully.
• Extra folds of skin on arms and legs.
• A large head with a prominent forehead and a flat face.
• Short stature (skeletal dysplasia) and very short arms and legs (micromelia).
• Wide-set eyes.

The leading cause of death among infants diagnosed with thanatophoric dysplasia is respiratory failure. This makes it difficult for a baby to breathe.

Babies who survive infancy may experience additional symptoms, including:

• Abnormal bone growth.
• Difficulty breathing.
• Hearing loss.
• Seizures.

What causes thanatophoric dysplasia?

A mutation (genetic change) of the FGFR3 gene causes thanatophoric dysplasia. The FGFR3gene is responsible for giving the fetus instructions to develop and maintain bones. Your body tells this gene to do its job by turning on a light switch. A mutation of the FGFR3 gene permanently leaves the gene’s light switch to stay in the on position. When this occurs, the proteins that make up the gene are overactive. This limits the growth and formation of bones from cartilage (ossification) in the long bones of the body.

Almost all cases of thanatophoric dysplasia are due to a mutation in FGFR3 that’s new to the fetus and not inherited from a biological parent. It’s typically not present in a person’s biological family. While rare, the gene change can pass from one biological parent to a fetus in an autosomal dominant pattern.

Who does thanatophoric dysplasia affect?

Thanatophoric dysplasia can happen to any child, as the gene change happens randomly. Very rarely, a child could inherit the mutation from a biological parent.

Genetic changes aren’t the result of something a biological parent did while pregnant to cause the condition.

How is thanatophoric dysplasia diagnosed?

Diagnosis for thanatophoric dysplasia begins during pregnancy and is typically detected on prenatal ultrasounds. Your healthcare provider will offer tests to identify possible genetic conditions during pregnancy. They’ll look for symptoms during prenatal ultrasounds like too much amniotic fluid surrounding the fetus (polyhydramnios) and bone growth symptoms.

If your healthcare provider finds a mutation of the FGFR3 gene after a test, they’ll take steps to avoid potential pregnancy complications.

After your baby is born, an X-ray of your baby’s bones and an ultrasound of their internal organs, especially their lungs, may be ordered to determine if any treatment for breathing might be helpful.

What tests diagnose thanatophoric dysplasia?

During pregnancy, your provider will offer different tests to diagnose genetic conditions. These tests include:

• Amniocentesis: Your healthcare provider will take a small sample of amniotic fluid to identify potential health conditions between 15 and 20 weeks of pregnancy.
• Chorionic villus sampling (CVS): Your provider will take a small sample of cells from your placenta to look for genetic conditions between 10 and 13 weeks of pregnancy.

How is thanatophoric dysplasia treated?

Babies who survive birth will immediately receive treatment to support underdeveloped lungs. This helps them breathe better. Respiratory support could include:

• Inserting a tube in their windpipe (tracheostomy).
• Receiving supplemental oxygen through their nostrils (continuous positive airway pressure or CPAP).
• Taking medicine to open airways (bronchodilators).
• Using a ventilator, which is a machine that helps get air into their lungs.

Additional treatments alleviate symptoms of the condition, including:

• Using hearing aids for hearing loss.
• Taking antiseizure medicine for seizures.
• Undergoing surgery to adjust bone growth abnormalities.

While most babies diagnosed with thanatophoric dysplasia don’t survive, your care team will recommend resources and support to comfort you and your loved ones through this diagnosis. Grief counseling or bereavement counseling helps individuals cope with loss and navigate challenging experiences that accompany a loss. Mental health providers are available to help you navigate grief as well.

How can I reduce my risk of having a child with thanatophoric dysplasia?

There’s no way to prevent thanatophoric dysplasia because it’s often the result of a new genetic mutation that occurs randomly. If you plan on becoming pregnant, talk with your healthcare provider about genetic testing to understand your risk of having a child with a genetic condition.

What can I expect if I have a baby diagnosed with thanatophoric dysplasia?

The prognosis (outlook) is poor for babies diagnosed with thanatophoric dysplasia. This is due to the underdevelopment of their lungs. Their life expectancy is short. Many babies are stillborn or don’t survive during their first few weeks of life.

Babies who survive undergo intensive care to support their lungs and stabilize their breathing. Ventilator use is necessary throughout childhood.

Losing a child is extremely difficult and painful. This outcome can have a significant impact on your emotional well-being and mental health. Support services are available for grieving parents and family members to cope with the loss.

How do I take care of myself if I have a child diagnosed with thanatophoric dysplasia?

Learning that your baby has thanatophoric dysplasia is challenging and difficult. Your care team will help you and your loved ones say goodbye. They’ll also provide follow-up care to make sure you and your family are doing as well as you can after the loss of your child.

If you feel sad, anxious, depressed or hopeless and are having a difficult time grieving the loss of your child, reach out to your healthcare provider. They can connect you to a mental health professional or a bereavement support group where you can share your feelings with others who’ve had similar losses. Surrounding yourself with a network of support can help you manage the grief you’re feeling.

When should I visit the ER?

If your child born with thanatophoric dysplasia has trouble breathing, has an irregularly fast heartbeat or their skin turns a blue, purple or a pale color around their lips, mouth and fingers, they’re showing signs of respiratory distress and a lack of oxygen. Call 911 (or your local emergency services number) or visit the emergency room immediately.

What questions should I ask my doctor?

• Can I get genetic testing done if I plan on becoming pregnant?
• If I try to have another child, is it likely that they’ll have thanatophoric dysplasia?
• Can you recommend resources to help me grieve the loss of my child?