Achondroplasia (ACH) is a disorder of the genes. The changes in the genes causes short stature and a large head. It is the most common cause of dwarfism.

People with ACH reach a full-grown height of around 4-4½ feet. The arm bone between the shoulder and the elbow and the leg bone between the hip and the knee are most affected. It may also affect how the face develops.


ACH is caused by a change in the FGFR3 gene. This gene controls how bones and cartilage grow. A defect in the gene prevents normal growth and leads to shorter and abnormally shaped bones.

The defect can occur suddenly, for no known reason. It early in pregnancy when the sperm and egg meet. The gene can also be passed through a family, though this is less common. If a parent has the defective gene, there is a 50% chance the child will have it. You can carry the gene and not have ACH.


Factors that may increase the chance of ACH include:

  • Parent with ACH
  • Parents without who carry a mutated FGFR3 gene
  • Advanced age of father


Characteristics of ACH include:

  • Short stature, a normal trunk, and shortened limbs, which are noticeable at birth
  • An adult height around 4-4½ feet
  • A head that is large and large forehead
  • Some of face may be underdeveloped
  • Knees have inward or bow-legged appearance once child starts to walk
  • Fingers and toes are short and stubby
  • Arm may not be fully straight at elbow
  • May be an excessive curve of the lower back
  • Waddling walking pattern
  • Problems with mouth like overcrowding of teeth

Other common symptoms include:

  • Weight control problems
  • Problems of the nervous system
  • Respiratory problems
  • Fatigue, pain, and numbness in the:
    • Lower back
    • Spine


Signs of ACH may be visible during prenatal testing. If the doctor suspects ACH, other tests may be recommended. An amniocentesis can remove a small amount of fluid from around the baby. Genetic testing can be done to confirm ACH.

After birth, the doctor will do a physical exam. Images of the bones may be taken with:

A genetic counselor can help you understand the risk of having a child with ACH. You may consider it if you have a family history or you know you have the altered gene.


At this time, there is no cure for ACH. The goal of treatment is to manage related health issues. The child's care team with check for common issues such as:

  • Problem with fluid around the brain—may be problems with amount or flow
  • Chronic ear infections
  • Sleep apnea
  • Orthopedic problems like excessive curve in spine, spinal stenosis, or bow legs.

Spinal Stenosis

Stenosis of spine with punched nerve
Copyright © Nucleus Medical Media, Inc.

Regular appointments will help to find any problems early. Early treatment may improve outcomes. General treatments may include:


Human growth hormone may help to increase adult height. It is given during childhood.


Surgery is sometimes needed to correct some bone deformities. Some common options include:

  • Spinal fusion—connect spinal bones for more stability
  • Laminectomy—remove parts of spinal bones to relieve pressure on the spinal cord
  • Osteotomy—to repair severe knock-knee or bowed legs
  • Bone lengthening—type of osteotomy. The bone is cut and fixed with a gap to encourage more growth in the bone. It is a lengthy and difficult process.


There are no steps to prevent ACH. The change in the gene appears random.