• Disease Overview
  • Synonyms
  • Signs & Symptoms
  • Causes
  • Affected Populations
  • Disorders with Similar Symptoms
  • Diagnosis
  • Standard Therapies
  • Clinical Trials and Studies
  • References
  • Programs & Resources
  • Complete Report



Last updated: December 08, 2021
Years published: 1986, 1990, 1992, 1993, 1994, 1995, 1997, 2001, 2004, 2007, 2018


NORD gratefully acknowledges Sarah Zhou, MD Candidate, McGill University School of Medicine, and Richard M. Pauli, MD, PhD, School of Medicine and Public Health, University of Wisconsin, for assistance in the preparation of this report.

Disease Overview


Achondroplasia is the most commonly occurring abnormality of bone growth (skeletal dysplasia), occurring in approximately 1 in 20,000-30,000 live births. This genetic disorder is caused by a change (mutation) in the fibroblast growth factor receptor 3 (FGFR3) gene. Achondroplasia occurs as a result of a spontaneous genetic mutation in approximately 80 percent of patients; in the remaining 20 percent it is inherited from a parent. This genetic disorder is characterized by an unusually large head (macrocephaly), short upper arms (rhizomelic dwarfism), and short stature (adult height of approximately 4 feet). Achondroplasia does not typically cause impairment or deficiencies in mental abilities. If the bones that join the head and neck do not compress the brainstem or upper spinal cord (craniocervical junction compression), life expectancy is near normal.

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  • ACH
  • achondroplastic dwarfism
  • dwarf, achondroplastic
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Signs & Symptoms

This rare genetic disorder is characterized by distinctive features: short stature (usually under 4 feet 6 inches); an unusually large head (macrocephaly) with a prominent forehead (frontal bossing) and flat (depressed) nasal bridge; short arms and legs; prominent abdomen and buttocks (due to inward curve of the spine); and short hands with fingers that assume a “trident” or three-pronged position during extension.

Infants born with achondroplasia typically have a “dome-like” (vaulted) skull, and a very broad forehead. In a small proportion there is excessive accumulation of fluid around the brain (hydrocephalus). Low muscle tone (hypotonia) in infancy is typical of achondroplasia. Acquisition of developmental motor milestones may be delayed.

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Achondroplasia results from specific changes (mutations) of a gene known as fibroblast growth factor receptor 3 (FGFR3).

For most patients, there is no apparent family history of the condition. Increased age of the father (advanced paternal age) may be a contributing factor in cases of sporadic achondroplasia.

Less commonly, familial cases of achondroplasia follow an autosomal dominant pattern of inheritance. Dominant genetic disorders occur when only a single copy of an abnormal gene is necessary to cause a particular disorder. The abnormal gene can be inherited from either parent or can be the result of a mutated (changed) gene in the affected individual. The risk of passing the abnormal gene from an affected parent to an offspring is 50% for each pregnancy. The risk is the same for males and females.

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Affected populations

Achondroplasia appears to affect males and females in equal numbers. This disorder begins in the developing fetus and is one of the most common forms of skeletal dysplasia that causes dwarfism. The estimated frequency of achondroplasia has ranged from about one in 15,000 to one in 35,000 births.

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Clinical and radiologic features of achondroplasia are well-characterized. Those with typical findings generally do not need molecular genetic testing to confirm the diagnosis. When clinical features raise suspicion in a newborn, X-ray (radiography) findings can be used to help confirm the diagnosis. However, if there is uncertainty, identification of the genetic variant of the FGFR3 gene by molecular genetic testing can be used to establish the diagnosis. Below is a list adapted from Pauli and Legare (2018) that provides clinical signs that may be used in the diagnosis of achondroplasia.

  • Disproportionate short stature
  • Macrocephaly with frontal bossing
  • Backward displacement of the midface and depressed nasal bridge
  • Shortening of the arms with redundant skin folds on limbs
  • Limitation of elbow extension
  • Shortened fingers and toes (brachydactyly)
  • Trident configuration of the hands
  • Bow legs
  • Exaggerated inward curve of the spine (lumbar lordosis)
  • Joint laxity
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Standard Therapies

Recommendations for managing children with achondroplasia are outlined by the American Academy of Pediatrics Committee on Genetics, which are designed to supplement guidelines for children with average stature.

As outlined in Pauli and Legare (2018), the recommendations for the manifestations of achondroplasia include:

  • Hydrocephalus: If signs/symptoms of increased intracranial pressure arise (accelerated head growth, bulging fontanelle, vision changes, headache), referral to a neurosurgeon is required. Computerized tomography (CT) or magnetic resonance imaging (MRI) of the brain in infancy may be done to determine the presence of hydrocephalus.
  • Craniocervical junction constriction: Predictors of the need for suboccipital decompression require evaluation by a medical professional. Indication of symptomatic compression requires urgent referral to a neurosurgeon.
  • Obstructive sleep apnea: Can be treated with weight reduction, surgery to remove tonsils and adenoids (adenotonsillectomy), positive airway pressure, and, rarely, surgery to create an opening in the neck (tracheostomy).
  • Middle ear dysfunction: Ear tubes may be needed until the age of seven or eight to manage frequent middle ear infections and prevent potential hearing loss.
  • Short stature: Studies on the use of growth hormone have shown initial acceleration of growth, but with lessening effect over time and little lasting benefit.
  • Obesity: Measures to avoid obesity should begin in early childhood. Standard weight-by-height grids specific for achondroplasia should be used to monitor progress.
  • Varus deformity: Symptomatic bowing of the legs (varus deformity) requires referral to an orthopedist. However, asymptomatic bowing does not usually warrant surgical correction.
  • Spinal deformities: Preventive measures including prohibition of unsupported sitting in the first 12-18 months of life decrease risk of developing a fixed backwards curve in the mid-spine (kyphosis). Bracing or surgery may be necessary, depending on the degree of severity of such a deformity if preventive measures are unsuccessful.
  • Spinal stenosis: If signs/symptoms of spinal stenosis arise, urgent surgical referral is appropriate.
  • Immunization: All routine immunizations are necessary.
  • Adaptive needs: Environmental modifications of the home and school may be necessary to accommodate for short stature.
  • Socialization: Patients with achondroplasia may encounter difficulties in socialization and school adjustment. Support groups (such as Little People of America) can help assist families with these issues through peer support, personal example, and social awareness programs.

In 2021, Voxzogo (vosoritide) was approved for children five years of age and older with achondroplasia and open epiphyses (growth plates), allowing the potential for growth.

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Clinical Trials and Studies

Information on current clinical trials is posted on the Internet at https://clinicaltrials.gov/. All studies receiving U.S. Government funding, and some supported by private industry, are posted on this government web site.

For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:

Toll-free: (800) 411-1222
TTY: (866) 411-1010
Email: [email protected]

Some current clinical trials also are posted on the following page on the NORD website:

For information about clinical trials sponsored by private sources, contact:

For information about clinical trials conducted in Europe, contact:

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Pauli RM, Botto LD (2018) Achondroplasia. In: Management of Genetic Syndromes. 4 ed. New York, NY: John Wiley & Sons. In press.

Miccoli M, Bertelloni S, Massart F. Height outcome of recombinant human growth hormone treatment in achondroplasia children: a meta-analysis. Horm Res Paediatr. 2016;86:27–34.

Pauli RM, Legare JM. Achondroplasia. 1998 Oct 12 [Updated 2018 May 10]. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2018. Available from: https://www.ncbi.nlm.nih.gov/books/NBK1152/ Accessed July 26, 2018.

Bober MB, Bellus GA, Nikkel SM, et al. Hypochondroplasia. 1999 Jul 15 [Updated 2013 Sep 26]. In: Adam MP, Ardinger HH, Pagon RA, et al., editors. GeneReviews® [Internet]. Seattle (WA): University of Washington, Seattle; 1993-2018.Available from: https://www.ncbi.nlm.nih.gov/books/NBK1477/ Accessed July 26, 2018.

Bacino C. Achondroplasia. UpToDate. topic last updated: Nov 15, 2017. https://www.uptodate.com/contents/achondroplasia Accessed July 12, 2018.

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Programs & Resources

RareCare® Assistance Programs

NORD strives to open new assistance programs as funding allows. If we don’t have a program for you now, please continue to check back with us.

Additional Assistance Programs

MedicAlert Assistance Program

NORD and MedicAlert Foundation have teamed up on a new program to provide protection to rare disease patients in emergency situations.

Learn more http://rarediseases.org/patient-assistance-programs/medicalert-assistance-program/

Rare Disease Educational Support Program

Ensuring that patients and caregivers are armed with the tools they need to live their best lives while managing their rare condition is a vital part of NORD’s mission.

Learn more http://rarediseases.org/patient-assistance-programs/rare-disease-educational-support/

Rare Caregiver Respite Program

This first-of-its-kind assistance program is designed for caregivers of a child or adult diagnosed with a rare disorder.

Learn more http://rarediseases.org/patient-assistance-programs/caregiver-respite/

Patient Organizations

IAMRARE® Patient Registry

Powered by NORD, the IAMRARE Registry Platform® is driving transformative change in the study of rare disease. With input from doctors, researchers, and the US Food & Drug Administration, NORD has created IAMRARE to facilitate patient-powered natural history studies to shape rare disease research and treatments. The ultimate goal of IAMRARE is to unite patients and research communities in the improvement of care and drug development.

Learn more >