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Achondroplasia

(Achondroplastic Dwarfism)

Definition

Achondroplasia (ACH) is a genetic bone disorder. It is the most common type of dwarfism. Key features are a large head, short limbs, a narrow chest, and short fingers.

Causes

ACH is caused by changes (mutations) in the FGFR3 gene. These changes prevent normal growth. This also leads to shorter and abnormally shaped bones.

Risk Factors

This problem can happen in people who do not have any known risk factors.

The gene changes can also be passed through a family, though this is not as common. If a parent has the gene mutations, there is a 50% chance the child will have it.

Things that may raise the risk are:

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

Symptoms

Problems are often seen at birth. Key features are a large head, short limbs, a narrow chest, and short fingers.

Other problems may be:

  • Short stature—adult height will be 4 to 4½ feet
  • Bowlegs
  • Short toes
  • Underdeveloped parts of the face
  • Arms that may not be fully straight at the elbow
  • An excessive lower back curve

Diagnosis

A prenatal ultrasound may point to ACH. Genetic testing may be done to confirm it.

ACH may also be suspected during a physical exam at birth. It can be confirmed through x-rays. Rarely, genetic testing may be done if the exam and x-rays are not certain.

Treatment

There is no cure. The goal of treatment is to manage related health problems. Some options are:

Medication

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

Surgery

Some people may need surgery to treat related health problems. Some common options are:

  • Spinal fusion —connects spinal bones to make them more stable
  • Laminectomy —removes parts of spinal bones to ease pressure on the spinal cord
  • Osteotomy—repairs severe bowlegs
  • Bone lengthening—cuts and divides a bone to encourage more growth

Counseling

Families may be referred to support groups.

Prevention

There are no known guidelines to prevent ACH.

RESOURCES:

Healthy Children—American Academy of Pediatrics
http://www.healthychildren.org

Little People of America
http://www.lpaonline.org

CANADIAN RESOURCES:

Caring for Kids—Canadian Paediatrics Society
http://www.caringforkids.cps.ca

Little People of Ontario
http://www.lpo.on.ca

REFERENCES:

Achondroplasia. EBSCO DynaMed website. Available at:https://www.dynamed.com/condition/achondroplasia. Accessed September 16, 2020.

Achondroplasia. Genetic and Rare Diseases Information Center website. Available at: https://rarediseases.info.nih.gov/diseases/8173/achondroplasia. Accessed September 16, 2020.

Pauli, RM, Legare JM. Achondroplasia. GeneReviews 2018 May 10.

Last reviewed March 2020 by EBSCO Medical Review Board Kari Kassir, MD  Last Updated: 9/16/2020