Achondroplasia

What is Achondroplasia?

Achondroplasia is a bone growth disorder that causes dwarfism.

Dwarfism is defined as a condition of short stature as an adult. People with achondroplasia are short in stature with a normal sized torso and short limbs. It’s the most common type of disproportionate dwarfism.

The word “achondroplasia” means “without cartilage formation.” Cartilage is the tissue that makes up much of the skeleton during early development. In achondroplasia, individuals have a problem with  how cartilage converts to bone (ossification), particularly in the extremities.

The average height of an adult male with achondroplasia is 4 feet, 4 inches while the average height for adult females is 4 feet, 1 inch.

What are the symptoms of Achondroplasia?

During early fetal development, much of the skeleton is made up of cartilage, which eventually converts to bone – except for those with achondroplasia.

Physical symptoms include:

• Short stature
• Short arms and legs
• Short fingers in which the ring and middle fingers may also point away from each other
• Disproportionately large head compared to the body
• Abnormally large forehead
• Underdeveloped area of the face between the forehead and upper jaw

Health problems include:

• Decreased muscle tone, which can cause delays in walking and other motor skills
• Apnea, which involves brief periods of slowed breathing or breathing that stops
• Hydrocephalus, or “water on the brain”
• Spinal stenosis

Children and adults with achondroplasia may experience or develop:

• Difficulty bending elbows
• Obesity
• Chronic ear infections
• Bowed legs
• Abnormal curvature of the spine

What causes Achondroplasia?

Achondroplasia is caused by mutations in the FGFR3 gene.  The FGFR3 gene instructs the body to make a protein necessary for bone growth and maintenance. Mutations in the FGFR3 gene cause the protein to become overactive, which interferes with normal skeletal development.

Most cases of the genetic mutation is random, while in some cases, it is inherited. In these cases, it is an autosomal dominant inheritance.

How is Achondroplasia diagnosed?

Achondroplasia is diagnosed by characteristic clinical and X-ray findings.

Furthermore, genetic testing can be used to identify a mutation in the FGFR3 gene.  Genetic testing can identify mutations in 99 percent of individuals who have Achondroplasia. Testing for the FGFR3 gene mutation is available in clinical laboratories.

What are the treatments for Achondroplasia?

No specific treatment is available for Achondroplasia.

Related abnormalities, including spinal stenosis and spinal cord compression, can be treated when they cause problems.

Where can I find out more about Achondroplasia?

• NIH
• National Organization for Rare Diseases (NORD)
• National Human Genome Research Institute
• The MAGIC Foundation