What is pseudoachondroplasia?

Pseudoachondroplasia is a rare, inherited disorder that affects bone growth. It affects one in 30,000 people. The condition is also referred to as pseudoachondroplastic dysplasia or pseudoachondroplastic spondyloepiphyseal dysplasia. It is a form of dwarfism.

People with pseudoachondroplasia have normal intelligence, head size, and facial features. However, they are small in stature: an average male is around 3 feet 11 inches tall and a female about 3 feet 9 inches.

Signs of pseudoachondroplasia are not visible at birth; they usually develop around the age of 2 or 3 when a child’s growth rate decreases due to the disorder.


Pseudoachondroplasia is caused by mutations in a gene called cartilage oligomeric matrix protein (COMP). Normally, COMP is found in the spaces between cartilage-forming cells called chondrocytes where it works with other proteins. When there is a mutation in the COMP gene, abnormal protein builds up inside the chondrocyte. This leads to early cell death and prevents normal bone growth.

Most cases of pseudoachondroplasia result from new mutations of the gene and occur in families with no history of the disorder, however, pseudoachondroplasia can be inherited. The condition follows an autosomal dominant pattern, meaning if one parent has the disorder, each of their children has a 50 percent chance of inheriting it.

Signs and symptoms

Signs of pseudoachondroplasia can vary from child to child, but may include:

  • Short arms and legs
  • Delay in crawling and walking
  • Waddling walk
  • Joint pain at an early age
  • Limited range of motion at the elbows and hips
  • Abnormally large range of joint movement (hyperextendibility) in the hands, knees and ankles
  • Knee deformities, such as bow-legs (knees that point outward) or knock-knees (knees that point inward)
  • Curvature of the spine, including scoliosis or lordosis, an inward curvature of the cervical (top) and lumbar (middle) portions of the spine

Testing and diagnosis

Diagnostic evaluation usually begins with a thorough medical history and physical examination of your child. At Children’s Hospital of Philadelphia (CHOP), clinical experts use a variety of diagnostic tests to diagnose pseudoachondroplasia and possible complications, including:

  • X-rays, which produce images of bones.
  • Magnetic resonance imaging (MRI), which uses a combination of large magnets, radiofrequencies and a computer to produce detailed images of organs and structures within the body.
  • Computed tomography (CT) scan, which uses a combination of X-rays and computer technology to produce cross-sectional images ("slices") of the body.
  • Genetic testing, in which a sample of your child’s saliva or blood is used to identify your child’s DNA.
  • EOS imaging, an imaging technology that creates 3-dimensional models from two planar images. Unlike a CT scan, EOS images are taken while the child is in an upright or standing position, enabling improved diagnosis due to weight-bearing positioning.

All of these tests allow clinicians to gather a full picture of your child’s medical health and help them decide on an individualized care plan.


Treatment for pseudoachondroplasia varies because the condition affects several body systems, and each child’s case is different. Some children will only require careful monitoring. Others will need, non-surgical or surgical treatments to address specific aspects of their condition.

At Children’s Hospital of Philadelphia, we practice collaborative, family-centered care. A team of expert clinicians — including leading orthopaedic surgeons and physicians, pediatric nurses, physical and occupational therapists, psychologists and other specialists — will partner with you in the care of your child.

Many children with pseudoachondroplasia are also diagnosed with a variety of orthopaedic conditions including: scoliosis, hip pain, joint stiffness and limb shortening. In most cases, these conditions only become evident – or problematic – as your child grows. Depending on your child’s needs, orthopaedic specialists from our Spine Program, our Hip Disorders Program and/or our Leg and Foot Program will treat your child.

Every child’s condition is different, so treatment is determined on a case-by-case basis. For example, if your child has scoliosis, our team of specialists will consider the severity of the curve, where it occurs in the spine, and your child's age and stage of growth, before determining the best course of action.

Treatment may include non-surgical options such as bracing and physical therapy, or surgical options such as spinal fusion or implanting growing rods to stabilize your child’s spine as he continues to grow.

For other effects of pseudoachondroplasia, in general, treatment may include:

  • Bracing and/or surgery for scoliosis
  • Medication or pain relievers for joint pain
  • Bracing and/or surgery for knee and lower-leg deformities
  • Bracing and/or surgery to treat hip pain
  • Physical therapy to help your child remain limber

Follow-up care

Your child with pseudoachondroplasia should be monitored by an orthopaedic physician throughout his development, into adulthood.

Doctors will watch for degenerative joint disease and neurological problems (such as weakness in an arm or leg), and assess lower-limb alignment and joint pain. It is not uncommon for children with pseudoachondroplasia to have legs that are slightly different lengths, which can affect the way the child walks (gait) in the short-term, and can affect hip function in adulthood.

If your child had spine, hip or leg surgery, he or she will need to see the orthopaedic surgeon about one to two weeks after surgery, then again at three and six months post-surgery. After that, annual monitoring by trained clinicians is strongly encouraged to ensure any problems are spotted and treated as soon as possible.

Additionally, physicians may recommend your child see several specialists because other body systems may be affected by pseudoachondroplasia.

For example, your child may see:

  • An orthopaedist for any bone-, muscle- and joint-related issues
  • Physical therapists and occupational therapists to expand your child’s physical dexterity and skill
  • A neurologist or neuromuscular specialist to address any nerve or muscle weakness
  • A psychologist or social worker to address any body-image and related mental health issues

During follow-up visits, X-rays and other diagnostic testing may be done. The goal of continued monitoring is to help spot any irregularities in growth or development and to address health issues as they develop.

Follow-up care and ongoing support and services are available at our Main Campus and throughout our CHOP Care Network. Our team is committed to partnering with parents and referring physicians to provide the most current, comprehensive and specialized care possible for your child.


Children with pseudochondroplasia can lead relatively normal lives. They have normal intelligence and an average life span.

Ongoing medical monitoring is important for people with pseudoachondroplasia. About half will eventually require hip replacement, and some may develop arthritis or further spine problems.

If you have questions about how your child’s condition and any related health issues may affect your child’s prognosis or long-term goals, talk to your child’s healthcare provider.

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