Achondroplasia Dwarfism: Rare Disease Health Guide

Medically Reviewed by Melinda Ratini, MS, DO on July 02, 2024
Written by Rachel Reiff Ellis
10 min read

Achondroplasia dwarfism is a bone growth disorder you have from birth. Achondroplasia means “no cartilage growth.” Cartilage is the strong, flexible connective tissue that protects your joints and bones. When you have the disorder, you don’t grow to a typical height.  

Achondroplasia vs. dwarfism (skeletal dysplasia)

Skeletal dysplasia is the broad term for conditions that cause problems with the way bones and cartilage grow. Achondroplasia dwarfism is the most common type of skeletal dysplasia. It’s the cause for 90% of cases of markedly short stature in people.  

Achondroplasia targets bone growth in the arms and legs.

Is achondroplasia hereditary?

It’s possible to inherit a gene for achondroplasia from one or both of your parents. The trait is autosomal dominant, which means there’s a 50% chance of getting it from a parent if one of your parents has the gene. But most cases aren’t inherited. 

Anyone can be born with achondroplasia. Most children – around 80% – born with it have a new (spontaneous) genetic mutation that happens before birth, and neither parent has the condition.

It’s also rare for people of normal height who have a child with achondroplasia to have another child with the disorder.

Achondroplasia risk factors

Achondroplasia is caused by a spontaneous mutation in a specific gene called FGFR3. About 98% of cases result from the exact same change in the DNA in this gene.

Achondroplasia happens in males and females equally. You may be at slightly higher risk if your father is 40 years or older when you’re born. 

Around 1 in every 20,000 to 30,000 babies born have achondroplasia. 

While everyone with the disorder will experience it slightly differently, there are some symptoms that are common.

  • Shortened thigh bone and upper arm bone
  • Short hands and feet
  • Short fingers
  • Larger than normal head size
  • Prominent forehead that curves outward above the eyebrows (frontal bossing)
  • Flattened bridge of the nose
  • Bowlegs (knees splay out) or knock-knees (knees turn in)
  • Limited elbow mobility and loose joints everywhere else
  • Large separation between the middle finger and ring finger (trident hand)
  • Curvature of the spine

What’s the first sign of achondroplasia?

At birth, babies with achondroplasia have a bigger than usual head with a broad forehead and flatter face. Their chests are slightly narrow and arms and legs are shorter than normal. 

What are the long-term symptoms of achondroplasia?

As children with achondroplasia get older, it can cause:

  • Delayed growth and motor milestones
  • Sleep apnea
  • Frequent ear infections
  • Obesity
  • Crowded or crooked teeth
  • Smaller than usual vertebral spaces that can lead to spinal compression

A small percentage of babies born with achondroplasia have fluid buildup in the brain (hydrocephalus). 

Most adults with achondroplasia grow to be around 4 feet 6 inches or less. 

Doctors can diagnose achondroplasia during pregnancy using ultrasound imaging to measure bones. DNA testing can confirm the diagnosis. Typically doctors do this if one or both parents have achondroplasia themselves. 

Testing for achondroplasia

To test DNA before birth, your doctor might use amniocentesis (using a needle to remove fluid from the amniotic sac for testing) or chorionic villus sampling (taking tissue from the placenta for testing).

Most cases are diagnosed after birth. Typically, a physical exam is all that’s needed for a doctor to diagnose your child with the disorder. But because there are treatments now available for achondroplasia, some parents and doctors prefer a DNA confirmation so they can use those treatments.

DNA testing looks for a mutation in the FGFR3 gene.

To diagnose your child with achondroplasia, a doctor may order several tests, including:

  • X-rays
  • MRI or CT scan to identify muscle weakness or spinal cord compression

What to expect after a diagnosis

If your baby is diagnosed with achondroplasia, their doctor will monitor them closely for their first 2 years of life. 

Children with achondroplasia tend to crawl and walk later than children without the disorder. They’re also prone to more ear infections. They may need X-rays periodically to look at their spine for compression issues.

When you get a diagnosis for achondroplasia, you’ll likely have many questions for your doctor. You might ask:

How does a child get achondroplasia?

Your doctor can explain the cause of your child’s achondroplasia. If you’ve had genetic testing, they can go over the results.

What’s the life expectancy of someone with achondroplasia?

Most people with the disorder live a normal life span, but there are factors that can affect this. If the disorder causes the bones that join the head and neck to compress the brain stem or upper spinal cord (craniocervical junction compression), this can shorten life expectancy. 

Can two parents with achondroplasia have an average-height baby?

People who have achondroplasia have one gene for the disorder and one gene for "average size." If both parents have achondroplasia, there’s a 25% chance their child will get a non-achondroplasia gene from each parent and be average size. 

Does achondroplasia affect IQ?

Even though the disorder can affect physical development and motor skills, people born with achondroplasia have normal intelligence. 

What organs are affected by achondroplasia?

The primary effect on the body in achondroplasia is bone growth that prevents the changing of cartilage. In rare cases (around 5%), babies born with achondroplasia can get hydrocephalus (fluid buildup on the brain). 

People with achondroplasia are also at a higher risk of heart disease and death from heart disease. Between ages 25 and 35, that risk is 10 times higher than people without the disorder. 

Can achondroplasia be cured?

Because most cases come from unexpected new mutations, there is no way to cure or prevent achondroplasia. 

Other typical questions might include:

  • Does my child need diagnostic tests?
  • What specialists will we need to see?
  • Are there screenings for symptoms or complications that my child will need?
  • Can you suggest educational materials and local support services for dwarfism?

Your child can live a full and healthy life with achondroplasia. The disorder itself does not need treatment, but doctors are working on medicines that promote bone growth, as well as gene therapy. 

Most of achondroplasia management involves monitoring symptoms caused by the disorder and treating any that interfere with health or daily activities. 

Managing achondroplasia symptoms

C-type natriuretic peptide (CNP) analog (vosoritide) is a medication you take by injection that can help increase bone growth. It is approved for children of any age with open growth plates. Other medications to increase height are in development.

Some doctors may prescribe growth hormones, but this doesn’t typically add significant height for people with achondroplasia. 

If sleep apnea is a problem, you can use a continuous positive airway pressure (CPAP) nasal mask that helps get more oxygen to the body while you sleep.

Weight management is part of achondroplasia care. Obesity is common, and maintaining a healthy weight can also help with sleep apnea. 

Some kids may need tubes in their ears to help with frequent ear infections and prevent hearing loss. 

Sometimes people with achondroplasia have a curved spine and may need a brace or even surgery to help straighten it.

Procedures for achondroplasia

You may need surgical help with some of the complications of achondroplasia. Some surgeries you might need include:

  • Surgery to remove your adenoids and tonsils to help with breathing
  • Surgery to lengthen legs or correct bowing of the legs
  • Procedure to put a shunt in the brain to decrease fluid pressure in case of hydrocephalus
  • Surgery to relieve the narrowing of the spine

Children diagnosed with achondroplasia can thrive. There are ways you can support their development and create a healthy environment for them. 

Provide a safe ride. Infants need a car seat with firm neck and back supports that face the rear of the car. Children and even adolescents need car seats or boosters longer than children without achondroplasia. 

Support loose joints. Use equipment for your baby that holds them safely. Avoid swings, strollers, slings, or jumper seats that don’t brace their neck or curve their back into a C shape. Always hold their head and neck safely as they’re developing muscles to support their head on their own.  

Watch for complications. Know what problems to look for, such as ear infections and sleep apnea. 

Adapt your home for shorter height. If you’re a parent of average height, your home will need modification so it’s accessible to your child as they get older. You can make changes such as putting extensions on light switches, lowering rails on stairs, supplying stools, and buying other adaptive products. 

Stay on top of your child’s health with regular checkups with the pediatrician to look for issues that can arise with the disorder.  

Almost all people with achondroplasia have a normal life span and normal intelligence. While some complications can happen, and certain symptoms may need management, you can live a full life with the disorder. 

Achondroplasia complications

Certain brain and spine issues can happen as children grow faster than their bones, especially the bones at the base of the skull and spine. If the spinal cord and brain stem are compressed, complications can happen. These include:

Cervicomedullary myelopathy. The small hole at the base of the skull where the spinal cord extends from the brain down along the spine is called the foramen magnum. When compression happens here, it “kinks” the brain stem, causing symptoms such as numbness, weakness, problems eating and sleeping, loss of bladder control, and trouble walking.

Compression of the brain stem can cause death if it’s not treated. It’s important to know the symptoms and call your doctor right away if you see them. 

Hydrocephalus. The fluid that surrounds your brain and spinal cord is meant to flow freely. When narrowing at the base of the skull blocks the flow, the fluid collects in spaces of the brain called ventricles. 

If your baby has this, you’ll notice their head getting larger in a short amount of time. Your child may also have headaches, be irritable, vomit, or be lethargic. A doctor can diagnose the problem with an MRI or CT scan.

Spinal cord myelopathy. Vertebrae that don’t grow enough can press on nerves coming in and out of the spinal cord. Depending on which nerve is compressed, your child may have numbness or tingling in one arm or leg. They may favor one side over the other, or complain of back pain. 

Sometimes, spinal cord myelopathy can cause bladder and bowel issues. 

In addition to your health care team, you may find connection and support through organizations focused on growth disorders. You can find information and support for people with achondroplasia and their families at:

Human Growth Foundation has social media groups for people to stay current on all things related to growth and bone disorders. You can also find private member-based groups and discussion forums. 

Little People of America is a national nonprofit organization with over 7,500 members that provides support and information to people of short stature and their families. They offer information on employment, education, disability rights, adoption, medical issues, clothing, adaptive products, and the many stages of parenting a short-statured child from birth to adult. 

The MAGIC Foundation is a charitable nonprofit organization created to provide support services for the families of children afflicted with a wide variety of chronic or critical disorders, syndromes, and diseases that affect a child's growth.  

Understanding Dwarfism is an online resource “dedicated to changing the world’s perception of a group of people who throughout history have been misunderstood and stigmatized because of their profound short stature.” Their resources educate families and others with personal stories, facts about people of short stature, and advocacy materials.

It can be hard for kids to look different from their peers. As your child grows, they may grapple with stares or even bullying. You can support their emotional growth and give them tools to thrive.

Talk about achondroplasia as normal. It’s a difference, not a problem. Help your child understand that they’re just right the way they are. 

Be age-appropriate. Small doesn’t always mean young or immature. Treat your child according to their age and not their size. Other people may need encouragement to do the same.

Have set answers to questions. When other people ask about your child’s height, have a script ready. You can say “They’re shorter than you are because their bones grow at a different speed than yours do.” 

Teach your child to report bullying. Let them know that it’s not OK if someone is teasing them and that an adult needs to know about it.

Educate your child’s teachers and caregivers about achondroplasia. The more they know, the better they can support your child at school or daycare.

Watch for signs of stress. Check in with your child and take note if they’re no longer doing things they enjoy, sleeping more than usual, or showing other signs of emotional distress. 

You may see several different types of specialists when you have achondroplasia. In addition to your child’s pediatrician, who will give them routine care and monitor overall health, other specialists can help you manage some of the symptoms and complications of the disorder.

These include:

  • An orthopedic surgeon for bone problems
  • A genetics doctor to help you understand how genes are involved in your child’s diagnosis and recommend future care
  • A pulmonologist if you’re dealing with sleep apnea
  • An ear, nose, and throat doctor (ENT or otolaryngologist) to keep tabs on extra fluid and infection in ears 
  • A neurosurgeon for brain and spinal cord problems
  • An occupational therapist for help with writing, eating, and other everyday activities
  • An endocrinologist, who can help with hormone-related issues
  • A developmental therapist, who specializes in therapy to help your child develop age-appropriate behaviors, social skills, and interpersonal skills
  • An orthodontist, who can help correct bite and teeth issues
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