What Is Achondroplasia? Resources + Tools
What Is Achondroplasia? Resources + Tools

What Is Achondroplasia?

What Is Achondroplasia?

Introduction

Achondroplasia is the most common type of skeletal dysplasia, occurring in about 1 in every 25,000 people. It is a rare genetic condition caused by a change in the FGFR3 (fibroblast growth factor receptor 3) gene, which slows bone growth, leading to disproportionate short stature. Children and adults with achondroplasia can lead healthy, happy, and fulfilling lives. Some may also face certain health needs associated with bone growth and development, which can be managed with the right care and support.

How Does Achondroplasia Impact Bone Growth?

Chondrocytes (cartilage cells) are a type of cell in the bones that are essential for growth and development. These cells contain a protein called FGFR3. FGFR3 plays an important role in how the bones in the body grow.

FGFR3’s job is to work like brakes on a car, slowing down bone growth.

In typical growth and development, it helps control the car’s speed (or regulate bone growth)—not too fast or too slow.

In achondroplasia, the genetic change causes FGFR3 to be overactive—acting like a brake that is pressed too hard and for too long.

Instead of keeping bone growth steady, the extra braking slows bone growth too much, which leads to short stature, shorter arms and legs, and other distinct physical features.

Is Achondroplasia Genetic?

Achondroplasia is a genetic condition, but it doesn’t always run in the family

Achondroplasia is passed down in an autosomal dominant manner. This means a child only needs to inherit the achondroplasia gene from one parent to be born with achondroplasia. A genetic counselor can help you understand your likelihood of having a child with achondroplasia.

Understanding your chances of having a
child with achondroplasia

If one parent has achondroplasia: There is a 50% chance their child will be born with achondroplasia

Understanding your chances of having a
child with achondroplasia

If both parents have achondroplasia: There is a 50% chance their child will be born with achondroplasia

Understanding your chances of having a
child with achondroplasia

If both parents have achondroplasia: There is a 25% chance their child will be born without achondroplasia

Understanding your chances of having a
child with achondroplasia

Average-height parents who have a child with achondroplasia have a less than 1% chance of having another child with achondroplasia

How Is Achondroplasia Diagnosed?

Achondroplasia is typically diagnosed in early infancy, but in some cases may be diagnosed prenatally (before birth).

Before Birth (prenatal)

Typical features, such as shorter arms and legs and a larger head size, can usually be seen on ultrasound after about 24 weeks of pregnancy.

After Birth (postnatal)

Babies with achondroplasia often have shorter upper arms and thighs, a larger head with a prominent forehead, and a smaller midface. Their chest may be smaller and their fingers are short, sometimes with extra space between the middle and ring fingers (sometimes called a “trident hand”). They may also have joints that are more flexible than usual at the hips and knees and lower muscle tone.

X-rays can show bones that are shorter and wider than average, with characteristic changes in the spine, pelvis, and skull. For example, the opening at the base of the skull (foramen magnum) may be smaller, and the lower back bones can appear closer together.

Genetic Testing

Genetic testing can play an important role in diagnosing and managing achondroplasia. A specific change (variant) in the FGFR3 gene is found in almost all people with achondroplasia, so testing can confirm the diagnosis with very high accuracy. This is helpful because it can rule out other similar bone conditions, provide clarity for families, and guide medical care.

There are a few ways testing can be done: during pregnancy (such as through noninvasive blood testing or when an ultrasound shows certain findings), shortly after birth to confirm what doctors see on exam or imaging, or even before pregnancy in special cases like in vitro fertilization or when there is a family history. Parents may also be offered testing if one of them has achondroplasia or if there is a chance of recurrence.

The benefits of genetic testing include:

  • Confirming a clinical diagnosis of achondroplasia
  • Helping doctors distinguish it from other skeletal conditions
  • Providing useful information for care planning and future family decisions

Learn more:

How does achondroplasia affect health?

Not all children with achondroplasia will experience these health concerns, and some may experience others not listed here. If you have any questions about what you or your child are experiencing, talk with your health care provider.

Achondroplasia can affect health in different ways, including

  • Narrowing at the base of the skull (foramen magnum stenosis), which can lead to compression of the spinal cord and build-up of fluid in the brain (hydrocephalus)
  • Differences in shape of head and face as well as in the airways can contribute to chronic ear infections
  • Airway differences related to facial structure can affect breathing during sleep (obstructive sleep apnea). Sleep apnea can also have other causes and should be evaluated by your doctor
  • Narrowing of the spinal canal (spinal stenosis), causing compression on the spinal cord and nerves

To learn more about potential health needs at different stages of life, select an age group:

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HEAR FROM THE COMMUNITY

“My friends would describe me as someone with a big personality, very outgoing, and someone that always is smiling. I’m a people person, and I love making people happy.”

- Young adult living with achondroplasia

“Typically, with achondroplasia, people focus on height, but there are other important aspects of the condition that impact quality of life.”

- Father of a teenager living with achondroplasia

“My joy is seeing my child’s daily progress. There were many things she couldn’t do like other children. She is gradually becoming capable of those things, little by little. I realized that it’s okay to grow slowly.”

- Mother of a child living with achondroplasia

“Our daughter is a person. She has feelings. Yes, she may be physically different than other children or other people, but I think that it is important to be aware of those differences without necessarily calling attention to them.”

- Father of a teenager living with achondroplasia

“What I want to convey to society is that rare conditions exist, and there are many people in the world who need help. I genuinely wish that the world would be kinder. I hope people have a level of knowledge that allows them to understand the condition when they see a child that is smaller or looks different.”

- Mother of a child living with achondroplasia

“The greatest joy as a parent is seeing my son be energetic and cheerful. I hope that my son will continue to look forward proudly, hold his head high, and live confidently and cheerfully.”

- Mother of a child living with achondroplasia

“Really, we are just like everyone else. We may look different, but we like being treated like everyone else.”

- Teenager living with achondroplasia

“I see in my future pretty much what anyone else would: graduating school, graduating college, going on to a job I like, starting a family.”

- Teenager living with achondroplasia

“I would tell myself back then [at time of diagnosis], just take a deep breath and let go of the fear a little bit. Fear is normal. Once you are over that fear, you kind of just dive in. You dive into the information, and you educate yourself and learn everything you can learn about achondroplasia and really try to be your kid’s biggest advocate.”

- Mother of a teenager living with achondroplasia

“Having achondroplasia, you are going to come across challenges consistently. The way you are going to deal with them is really going to impact your life. Yes, I have challenges; obstacles get thrown at me all the time, but it’s the way of going about it and realizing there is so much more to life than having achondroplasia.”

- Young adult living with achondroplasia

“I was four years old when my younger brother was born. I was young and didn’t understand what achondroplasia was. I don’t care if my brother is tall or short. I was simply happy to have a younger brother.”

- Sibling of a person living with achondroplasia

“We were always outside, we always were being competitive, playing sports, just being kids.”

- Young adult living with achondroplasia

“We have relied heavily on the community. We are quite appreciative of the community and the resources that are available to help parents, siblings and individuals with achondroplasia. The diversity within this community has been quite enriching on many levels.”

- Father of a teenager living with achondroplasia

“What we have seen is that she has done a great job of adapting herself, getting creative, doing things a little bit differently, but she always finds a way to be successful.”

- Father of a teenager living with achondroplasia