What Is Hypochondroplasia?

Hypochondroplasia is a skeletal dysplasia. Skeletal dysplasias are conditions that cause problems with how cartilage and bone grow.

Children growing up with hypochondroplasia (hi-po-kon-dro-PLAY-zhuh) can live long, productive lives. Treatment can help with related problems, and new research offers hope for even better treatments.

What Are the Signs & Symptoms of Hypochondroplasia?

People with hypochondroplasia have short stature (height less than other people of the same age). They might also have:

• a larger head
• a stocky build
• arms and legs that are short compared with the body
• short fingers
• bow legs (knees curve out)
• curved spine

What Problems Can Happen?

Medical problems that someone with hypochondroplasia can have include:

• sleep apnea
• obesity
• seizures (temporal lobe epilepsy)
• learning disabilities
• in young children: a narrowing of the opening at the bottom of the skull (called foramen magnum stenosis)
• in adults: a narrowing of the lower spinal canal (called lumbar spinal stenosis)

Most children with hypochondroplasia do not have every sign and symptom listed here. There is a lot of variability. People who have hypochondroplasia should get regular medical checkups. This helps doctors find and treat any medical problems right away.

What Causes Hypochondroplasia?

Hypochondroplasia usually happens because of a gene mutation (change). It makes bones grow slower and end up shorter than they typically would be.

Sometimes no gene change is found even though someone has the signs and symptoms of hypochondroplasia. This doesn’t necessarily mean that someone does not have hypochondroplasia. Their gene change just might not be found by today’s technology. Or, they may have a change in a different gene that causes signs and symptoms like hypochondroplasia.

A child can inherit hypochondroplasia 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 hypochondroplasia can run in families.

How Is Hypochondroplasia Diagnosed?

Doctors might diagnose hypochondroplasia before birth with a prenatal ultrasound, genetic testing (through amniocentesis), and/or chorionic villus sampling (CVS).

Most of the time, doctors diagnose it at birth or early in childhood. If a child is shorter than other kids the same age, or has short arms and legs, doctors do an exam and tests to find the cause. These tests usually include X-rays and sometimes genetic testing.

Sometimes the growth differences are so small that hypochondroplasia is not diagnosed until later in life.

How Is Hypochondroplasia Treated?

There’s no cure for hypochondroplasia, but doctors and scientists are working on medicines that can help with bone growth. Gene therapies are also being studied.

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

• an orthopedic surgeon: for bone problems
• a neurologist/neurosurgeon: for brain and spinal cord problems
• a pulmonologist: for sleep apnea
• developmental pediatrician: for the screening and treatment of any learning problems
• a genetics doctor: to help families understand the genetic changes and recommend future care
• a pediatrician: for routine care
• an occupational therapist: for help with writing, eating, and other everyday activities

Treatments for hypochondroplasia may include:

• weight management (after 2 years of age)
• sleep apnea treatment
• surgery for leg bowing
• surgery for spinal stenosis, compression, or curvature

When Should I Call the Care Team?

It is important to call someone on your care team if your child:

• has a loss of motor skills (for example, has stopped crawling), or only uses one arm or leg
• has pain, tingling, numbness, or weakness in the arms or legs
• has seizures
• struggles in school
• has pauses in breathing while asleep or loud constant snoring

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 hypochondroplasia as a difference rather than a problem. Your attitude can help your child develop good self-esteem.
• Find ways to help your child 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 changes that will help your child, such as lower chairs with foot support.
• If someone asks a question about your child’s hypochondroplasia, answer as simply as possible. For example, if someone asks why your child is short, say, “Joseph is shorter because his bones do not grow as fast as yours.” Then, mention something special about your child. For example, “Nothing holds Joseph back. You should see his artwork.” This shows your child that many things make them special.
• 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.
• Encourage your child to find a hobby or activity to enjoy. Help them try different activities, like sports, music, art, computers, writing, and photography. Be sure to check with your doctor about any sports your child should avoid.

What Else Should I Know?

Your child can live a full and happy life. Regular medical care will help them 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:

• Understanding Dwarfism
  
• Little People of America