Hypochondroplasia

What is hypochondroplasia?

Hypochondroplasia is a genetic condition that slows bone growth, especially in the long bones of the arms and legs. This condition is a type of skeletal dysplasia, and depending on a person’s final height, can be considered a form of dwarfism. Hypochondroplasia is related to achondroplasia, another form of dwarfism and skeletal dysplasia, but the signs are usually less obvious.

What causes hypochondroplasia?

A change in the message sent by the FGFR3 gene, which helps turn cartilage into bone, causes hypochondroplasia. This gene change slows the bone growing process, called ossification, making the bones grow more slowly. Compared to achondroplasia, children with hypochondroplasia usually have faster bone growth, and are generally a bit taller.

Who gets hypochondroplasia?

A child can inherit hypochondroplasia from either parent if they also have the condition. However, most children have a new or spontaneous gene change, meaning neither parent passed along the genetic change.

How common is hypochondroplasia?

Somewhere between 1 in 15,000 to 40,000 people have the condition, although the exact number is unknown as not everyone with the condition gets diagnosed.

What are the signs and symptoms of hypochondroplasia?

Children with hypochondroplasia are shorter than people of their age, and their arms and legs are short compared to their body length, which is called disproportionate short stature. Other signs and symptoms of hypochondroplasia include:

• A larger head
• A stocky build, sometimes with broad shoulders
• Shorter fingers and toes
• Bowed legs where knees bend outwards
• An exaggerated S-shape to the curve in their back known as lumbar lordosis or swayback
• Learning differences
• Seizures

When should I reach out to my child’s care team?

It’s important to reach out to our skeletal dysplasia experts or your healthcare provider if you see the following signs in your child:

• Loss of motor skills like stopping crawling, or losing bladder or bowel control
• Complaints of pain, tingling, numbness or weakness in the arms or legs
• Struggling in school
• Pauses in breathing or loud constant snoring while asleep
• Seizures

How do we diagnose hypochondroplasia?

Providers don’t usually recognize hypochondroplasia at birth unless there’s a family history. Around two years old, most children with hypochondroplasia will fall behind the typical growth curve for height. We typically diagnose children between one and four years old. However, some people don’t receive a diagnosis until adulthood because the signs and symptoms can be subtle.

Our specialists in the Skeletal Dysplasia Program use a physical exam and X-rays to identify symptoms of the condition and diagnose hypochondroplasia. We also provide genetic counseling services and offer genetic testing to identify the condition at a genetic level.

How do we treat hypochondroplasia?

While there isn’t a cure for hypochondroplasia, many treatments relieve the symptoms caused by the diagnosis, including:

• A sleep study may find sleep apnea that we can treat through tonsil removal or a continuous positive airway pressure (CPAP) device
• Ear tube surgery for fluid build-up or constant ear infections
• Surgery for leg bowing
• Surgery for spinal stenosis, compression or curvature
• Nutritional and lifestyle consultations

Why choose Children’s Colorado for treatment of hypochondroplasia?

We created the first pediatric skeletal dysplasia program in the Rocky Mountain region. So our experience and understanding of how hypochondroplasia affects kids and families is unmatched. Our multidisciplinary approach  means your child can see many specialists in one place, at one time, to ensure a comprehensive care journey. We're also designated as a Rare Disease Center of Excellence by the National Designation of Rare Disorders, meaning we have an elite level of expertise and experience in treating rare conditions, including hypochondroplasia.

Our care also extends far beyond our walls to help bring families with skeletal dysplasia together. We work with many groups such as Little People of America to expand research, education and awareness of rare types of skeletal dysplasia.

Helpful resources

• Parent Toolkit: Managing Your Child's Medical Illness at School
• Little People of America
• Dwarf Athletic Association of America
• Courageous Parents Network
• Parent-to-Parent
• Family Voices
• Make-A-Wish Foundation