An Overview of Pseudoachondroplasia

This rare type of dwarfism affects 1 in 30,000 people

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Pseudoachondroplasia is a bone disorder and type of dwarfism. It is mainly characterized by an average head and face size but a short stature, typically under 4 feet tall for both men and women. Although pseudoachondroplasia is caused by a genetic mutation, signs of the disorder aren’t visible until around age 2 when a child’s growth rate begins to drastically decrease.

The disease can be inherited from a parent, but in most cases, it’s a result of a new gene mutation that has no tie or family history. Pseudoachondroplasia was first referenced in 1959 by doctors and was originally believed to be a type of spondyloepiphyseal dysplasia. It’s now its own disorder caused by specific gene mutations.

Pseudoachondroplasia is extremely rare, affecting 1 in 30,000 people.

Symptoms

Infants who have pseudoachondroplasia won’t show any signs of the disease until around 9 months through 2 years of age, when growth drastically slows down compared to the standard growth curve, ranking in the fifth percentile or less.

Children with pseudoachondroplasia will still walk within the average timeframe (between 12 and 18 months) but tend to waddle and have an irregular gait due to bone and hip abnormalities.

Other Signs

  • Detection of scoliosis
  • Abnormal curvatures in the spine, such as an S-shaped or inward curve
  • Cervical instability, with limited, strained, or abnormal neck motion
  • Joint pain, primarily in the hips, ankles, shoulders, elbows, and wrists
  • Limited range of motion at the elbows and hips
  • Hip displacement, with the hips coming out of the sockets
  • Knee deformities
  • Possible delay in crawling or walking

Your pediatrician will be closely monitoring your child with regular well visits every few months for the first year of their life and will flag any issues they see for additional monitoring and possible testing. If you are concerned about your child’s growth and development, make sure to discuss it with them.

Causes

Pseudoachondroplasia is caused by a mutation of the cartilage oligomeric matrix protein (COMP). The COMP gene is responsible for helping in the production of the COMP protein, which surrounds cells that make up ligaments and tendons, as well as the cells that aid in bone formation.

While a baby can inherit the gene defect if one or both of their parents have it, the mutation can also happen on its own with no family history.

Diagnosis

Because pseudoachondroplasia is extremely rare, a specialist may perform several tests on a child to confirm the diagnosis. These include a combination of x-rays, MRIs, CT scans, and in some cases EOS imaging—technology that can create a 3-D image and is taken when a child is standing upright, which can help doctors see weight-bearing positions and, in the case of dwarfism, help to diagnose the condition more accurately.

An arthrogram may also be used, which is when dye is injected into the hips, knees, or ankles to asses the cartilage. This is useful in diagnosing as well as for surgical planning once a diagnosis is established. Children who may have pseudoachondroplasia will also go through genetic testing to help identify any deformities in their DNA.

Treatment

Pseudoachondroplasia affects many body systems in any given child, so each treatment plan is personalized to the patient on a case-by-case basis. Since many children with pseudoachondroplasia also suffer from osteoarthritis and spine problems, these factors are taken into consideration before determining treatment.

Depending on the severity of the symptoms associated with pseudoachondroplasia, there are both surgical options, like spinal fusion and non-surgical options, such as braces for spinal support, physical therapy, and medication for joint pain.

Because each treatment plan is personalized, you should work closely with your child’s orthopedist, physical therapist, neurologist, and psychologist if needed to map out the best plan for them.

Even after a treatment plan is determined, your child's specialists will be monitoring them for degenerative joint diseases over time. Children with pseudoachondroplasia tend to have legs that are different lengths, which in the short-term affects their gait but in the long-term may cause hip issues. It's not uncommon for someone with pseudoachondroplasia to need hip or knee replacements as they get older, due to the gait problems associated with the disease.

Neurological problems may also occur over time, such as arm and leg weakness due to limited or abnormal neck motion, so even though an initial treatment plan will be determined, it's likely it will need to be altered over time to help adjust as the child grows and new issues arise.

Coping

People with pseudoachondroplasia have no intellectual disabilities or intelligence delays with the disease, but it can still be isolating to deal with. There are many organizations that can help give support and information to pseudoachondroplasia patients and their families, the primary one being Little People of America, a nonprofit for all types of dwarfism that focus on peer interaction, education, and scholarships and grants.

It may also be beneficial for someone with pseudoachondroplasia to get support from the arthritis community since joint pain is a large part of the disease. The Arthritis Foundation provides resources for those suffering from all types of arthritis, along with ways to get involved in the community and resources for dealing with arthritis in your relationships, at work, and with friends and family.

A Word From Verywell

While a diagnosis of pseudoachondroplasia will require life-long medical monitoring, children who have the disease have an average life span and with a proper treatment plan can expect to lead a relatively normal life. It can be stressful to see your child missing growth milestones at the pediatrician every few months, but by diagnosing the disease early on, you and your child will have the tools you need to handle the hurdles that come with pseudoachondroplasia, making it easier to live day-to-day life and find the support with the proper specialists and groups you need.

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Article Sources
  • Pseudoachondroplasia. Children’s Hospital of Philadelphia website.

  • Pseudoachondroplasia. National Institute of Health’s Genetic and Rare Diseases Information Center website. Updated October 30, 2012.

  • Pseudoachondroplasia. National Organization for Rare Disorders website. Updated 2017.

  • Gene Reviews. Pseudoachondroplasia. Updated August 16, 2018. 

  • Pseudoachondroplasia. U.S. National Library of Medicine Genetics Home Reference website. Updated October 30, 2018.