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What Is Pseudoachondroplasia?

Pseudoachondroplasia (sue-doe-ay-kon-druh-PLAY-zhuh) is a skeletal dysplasia. Skeletal dysplasias are conditions that cause problems with how cartilage and bone grow.

Children growing up with pseudoachondroplasia can live long and productive lives. Treatment can help with related problems, and new research offers hope for even better treatments.

What Are the Signs & Symptoms of Pseudoachondroplasia?

Children with pseudoachondroplasia have:

  • dwarfism (height less than 4 feet, 10 inches [145 cm] as an adult)
  • arms and legs that are short compared with the body
  • short fingers
  • waddling gait
  • unusually flexible joints (except for the elbows) 
  • a curved spine
  • bow legs (knees curve out) or knock-knees (knees curve in)
  • arthritis and joint pain

Pseudoachondroplasia does not affect thinking and learning abilities. Note: Pseudoachondroplasia is similar to achondroplasia but has a different genetic cause and leads to slightly different signs and symptoms.

What Problems Can Happen?

Pseudoachondroplasia can cause mild problems in some kids and more serious ones in others. Health problems vary with age, but can include:

  • instability of the neck bones, which can lead to spinal cord problems if not found and corrected
  • a curved spine that may need bracing or surgery
  • sleep apnea (breathing problems during sleep)
  • obesity

Kids who have pseudoachondroplasia should get regular health checkups. This helps doctors find and treat any medical problems right away.

What Causes Pseudoachondroplasia?

Pseudoachondroplasia happens because of a mutation (change) in a gene called COMP. This change causes a problem with how bone and cartilage grow. The bones end up shorter than they typically would be.

A child can inherit pseudoachondroplasia if either parent has it. But most children born with it have a new (or spontaneous) genetic mutation that happened before birth, and neither parent has the condition.

A genetic counselor can help families understand how the condition can run in families.

How Is Pseudoachondroplasia Diagnosed?

Kids with pseudoachondroplasia usually are noticeably shorter than other kids at around age 2. Then, doctors will do an exam and order tests to find the cause. Tests usually include X-rays and, sometimes, genetic testing.

How Is Pseudoachondroplasia Treated?

A team of specialists cares for people with pseudoachondroplasia. They usually include:

Treatments for pseudoachondroplasia might include:

  • avoiding repetitive pounding activities that can wear down joints and increase joint pain
  • taking hot baths (with swirling water, if possible) after a long day of activity to help with joint pain
  • taking ibuprofen or naproxen as needed for joint pain
  • weight management
  • sleep apnea treatment
  • surgery to straighten the legs
  • surgery for curvature of the spine or unstable neck bones
  • joint replacement in adulthood

When Should I Call the Doctor?

Call the doctor right away if your child has:

  • a loss of motor skills (for example, was crawling but has stopped)
  • pain, tingling, numbness, or weakness in the arms or legs
  • trouble peeing or pooping (after being toilet trained)

How Can Parents Help?

To help your child:

  • Treat your child according to their age, not their size, and encourage others to do the same.
  • Talk about pseudoachondroplasia as a difference rather than a problem. Your attitude can help your child develop good self-esteem.
  • Find ways to adapt. For example, get a light switch extender and a stepstool so your child can turn the lights on and off. Encourage school staff to make similar changes to help your child, such as lower chairs and/or feet support. The physical education teacher should let your child decide which activities are comfortable.
  • Teach your child that being teased or bullied is not OK. If they're teased or bullied at school, work with your child, teachers, and administrators to end it.
  • Answer questions from others as simply as possible. If someone asks why your child is short, for example, say, “Stephen is shorter because his bones grow differently.” Then, mention something special about your child. For example, “Nothing holds Stephen back. He’s the biggest sports fan I know.” This shows your child that many things make them special.
  • Get plenty of physical activity together as a family. If needed, choose or adapt the activity so your child can join in.

What Else Should I Know?

Your child can live a full and happy life. Regular medical care will help your child stay well and let doctors treat any health problems right away. Talk to anyone on the care team or a hospital social worker about resources that can help you and your child.

Support groups can be helpful for kids and their families. Ask the care team for recommendations. You also can find support and more information online at:

Reviewed by: Amy W. Anzilotti, MD
Date Reviewed: Apr 10, 2022

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