Pseudoachondroplasia (Dwarfism)

What is pseudoachondroplasia?

Pseudoachondroplasia is a form of dwarfism that impacts bone growth. This rare genetic disorder may be inherited (passed on in families) or occur randomly. People with pseudoachondroplasia have short stature, including arms and legs that are abnormally short. But they have typical facial features, head size and intelligence.

The disorder is sometimes called:

• PSACH.
• Pseudoachondroplastic dysplasia.
• Pseudoachondroplastic spondyloepiphyseal dysplasia syndrome.

How tall will I get with pseudoachondroplasia?

People born with pseudoachondroplasia aren’t short at birth. They usually start to fall behind on growth charts around age 2.

Eventually, everyone with the condition has short stature. Men and people assigned male at birth (AMAB) with pseudoachondroplasia reach an average height of 3 feet and 11 inches (1.19 meters). Women and people assigned female at birth (AFAB) reach an average height of 3 feet and 9 inches (1.14 meters).

What’s the difference between pseudoachondroplasia vs achondroplasia?

Both pseudoachondroplasia and achondroplasia are forms of dwarfism that impact bone growth. The two conditions used to be considered the same. But more recent research has shown that they’re two different types of dwarfism.

A mutation in a different gene causes achondroplasia, which also involves distinctive facial features.

How common is pseudoachondroplasia?

Pseudoachondroplasia is rare. Scientists estimate that 1 out of every 30,000 to 100,000 babies is born with pseudoachondroplasia.

What causes pseudoachondroplasia dwarfism?

A mutation (change) in a gene called cartilage oligomeric matrix protein (COMP) causes pseudoachondroplasia. COMP is important to cells that create cartilage called chondrocytes.

During normal fetal development, a lot of cartilage develops into bone. But some cartilage remains, serving as connective tissue and protecting the joints and ends of bones. If you have a COMP mutation, abnormal proteins build up inside chondrocytes. That makes the cells die early, causing problems in joints and preventing bones from growing normally.

Some COMP mutations leading to pseudoachondroplasia are inherited. A parent who has the condition has a 50% chance of passing it down to each child. One parent can pass it down even if the other parent doesn’t have the condition. But most mutations are spontaneous (random).

What are the symptoms of pseudoachondroplasia?

You can usually detect the signs of pseudoachondroplasia at birth. Facial features, head size and intelligence are all typical. But skeletal abnormalities start to appear when your child is 9 months to 3 years of age, then become more obvious throughout early childhood.

Over time, the following signs may develop:

• Bowed legs that curve outward, knock knees that curve inward or one of each (called windswept deformity).
• Curved spine, such as scoliosis or kyphosis.
• Joint laxity (looseness) in most joints, but stiffer elbows and hips.
• Joint pain that progresses to osteoarthritis.
• Odontoid hypoplasia, which involves underdevelopment at the top of your spine and can cause neck instability.
• Short hands and toes.
• Short stature.
• Skin folds.
• A walk that looks a bit like a waddle, due to skeletal abnormalities in your hips.

How is pseudoachondroplasia diagnosed?

A healthcare provider can diagnose pseudoachondroplasia based on a physical exam and X-rays that provide pictures of the bones and joints.

Genetic testing, which usually requires a small sample of blood, can confirm the genetic mutation. In a family with increased risk of pseudoachondroplasia, genetic testing can be performed on a fetus. This involves chorionic villus sampling or amniocentesis.

How is pseudoachondroplasia treated?

Treatment for pseudoachondroplasia depends on how severe the condition is and how healthy you are otherwise. You may only need to be monitored over time to make sure no complications occur. Or you may need treatment, which can include:

• Analgesics or other medications to lessen joint pain.
• Braces or surgery to correct a curved spine.
• Counseling to address the psychosocial effects of short stature.
• Genetic counseling for family members who may be affected.
• Physical or occupational therapy to help improve strength and the ability to perform everyday activities.
• Surgeries to correct bone and joint problems, such as hip replacement, other joint replacements and knee osteotomy.

Surgical fusion to connect two or more vertebrae and stabilize the neck and spine.

How can I prevent pseudoachondroplasia?

Because a genetic mutation usually causes pseudoachondroplasia, you can’t prevent it.

If you have the condition and get pregnant, there’s a 50% chance of passing on the gene to your baby. Prenatal genetic testing can check for the genetic mutation. Your healthcare provider may also recommend genetic counseling for close family members.

What is the outlook for people with pseudoachondroplasia?

Pseudoachondroplasia doesn’t affect intellectual development or lifespan. People with pseudoachondroplasia usually live active, productive lives. Most have families of their own.

How do I take care of myself or my child with pseudoachondroplasia?

To care for yourself or your child with pseudoachondroplasia:

• Attend all follow-up appointments to monitor health and catch complications early.
• Avoid activities that cause pain or put stress on your joints, such as contact sports and excessive jumping.
• Don’t bend your neck too much as it can contribute to spinal issues.
• Encourage physical activities that put less stress on bones and joints, like walking and swimming.

How can I help my child cope with pseudoachondroplasia?

Visible abnormalities such as short stature can make children feel self-conscious and affect their social interactions. To help:

• Consider meeting with a mental health professional to help your child understand their emotions.
• Discuss the condition openly with your child, using simple language.
• Discuss the disorder openly with the people your child interacts with frequently.
• Join a support group or national advocacy organization, where you can meet other families who understand.
• Make sure teachers provide a supportive plan for your child to learn and socialize, free from bullying.
• Practice how to respond to people who ask about it. For example, “I was born with a condition that made my bones stop growing.”

A note from Cleveland Clinic

Pseudoachondroplasia is a form of dwarfism that affects bone growth. It causes short stature, abnormally short arms and legs, joint pain and skeletal abnormalities. But your facial features and head size are as expected. If you or your child has pseudoachondroplasia, a healthcare team can help you prevent and treat complications. They can also help you understand the risk of passing the condition on to the next generation.