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Genetics Home Reference: your guide to understanding genetic conditions
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Achondroplasia

Reviewed June 2006

What is achondroplasia?

Achondroplasia is a disorder of bone growth. Although achondroplasia literally means "without cartilage formation," the problem is not in forming cartilage but in converting it to bone, particularly in the long bones of the arms and legs.

All people with achondroplasia have short stature. The average height of an adult male with achondroplasia is 131 centimeters (4 feet, 4 inches), and the average height for adult females is 124 centimeters (4 feet, 1 inch). Characteristic features of achondroplasia include an average-size trunk, short arms and legs with particularly short upper arms and thighs, limited range of motion at the elbows, and an enlarged head (macrocephaly) with a prominent forehead. Fingers are typically short and the ring finger and middle finger may diverge, giving the hand a three-pronged (trident) appearance. People with achondroplasia are generally of normal intelligence.

Health problems commonly associated with achondroplasia include episodes in which breathing slows or stops for short periods (apnea), obesity, and recurrent ear infections. In adulthood, individuals with the condition usually develop a pronounced and permanent sway of the lower back (lordosis) and bowed legs. Older individuals often have back pain, which can cause difficulty with walking.

How common is achondroplasia?

Achondroplasia is the most common type of short-limbed dwarfism. The condition occurs in 1 in 15,000 to 40,000 newborns.

What genes are related to achondroplasia?

Mutations in the FGFR3 gene cause achondroplasia.

The FGFR3 gene provides instructions for making a protein that is involved in the development and maintenance of bone and brain tissue. This protein limits the formation of bone from cartilage (a process called ossification), particularly in the long bones. Two specific mutations in the FGFR3 gene are responsible for almost all cases of achondroplasia. Researchers believe that these mutations cause the protein to be overly active, which interferes with skeletal development and leads to the disturbances in bone growth seen with this disorder.

How do people inherit achondroplasia?

Achondroplasia is inherited in an autosomal dominant pattern, which means one copy of the altered gene in each cell is sufficient to cause the disorder. About 80 percent of people with achondroplasia have average-size parents; these cases result from a new mutation in the FGFR3 gene. In the remaining cases, people with achondroplasia have inherited an altered FGFR3 gene from one or two affected parents. Individuals who inherit two altered copies of this gene typically have very severe problems with bone growth, and are usually stillborn or die shortly after birth from respiratory failure.

Where can I find information about treatment for achondroplasia?

You may find information on treatment or management of achondroplasia or some of its symptoms in the links below, particularly the links for Gene Reviews, MedlinePlus Encyclopedia, Educational resources, and Patient support.

Where can I find additional information about achondroplasia?

You may find the following resources about achondroplasia helpful. These materials are written for the general public.

  • MedlinePlus - Health information
    • Encyclopedia: Achondroplasia (http://www.nlm.nih.gov/medlineplus/ency/article/001577.htm)
    • Encyclopedia: Lordosis (http://www.nlm.nih.gov/medlineplus/ency/article/003278.htm)
    • Health Topic: Dwarfism (http://www.nlm.nih.gov/medlineplus/dwarfism.html)
  • Additional NIH Resources - National Institutes of Health
    National Center for Biotechnology Information: Genes and Disease (http://www.ncbi.nlm.nih.gov/books/bv.fcgi?rid=gnd.section.256)
  • Educational resources - Information pages
    • Ask the Geneticist: Inheritance of achondroplasia (http://www.askthegen.org/question.php?question_id=692)
    • Centre for Genetics Education (http://www.genetics.com.au/pdf/factsheets/fs38.pdf)
    • Children's Hospital Boston (http://www.childrenshospital.org/az/Site558/mainpageS558P0.html)
    • Department of Orthopaedic Surgery, Johns Hopkins University (http://www.hopkinsmedicine.org/orthopedicsurgery/achondroplasia.html)
    • KidsHealth from the Nemours Foundation (http://kidshealth.org/parent/medical/bones/dwarfism.html)
    • Madisons Foundation (http://www.madisonsfoundation.org/index.php/component/option,com_mpower/diseaseID,260/)
    • Nemours Foundation (http://www.nemours.org/hospital/de/aidhc/service/skeletal/disorder/achondroplasia.html)
    • Orphanet (http://www.orpha.net/consor/cgi-bin/OC_Exp.php?Lng=EN&Expert=15)
    • The Wellcome Trust (http://genome.wellcome.ac.uk/doc_WTD020861.html)
    • University of Virginia Health System (http://www.healthsystem.virginia.edu/UVAHealth/peds_diabetes/achondro.cfm)
  • Patient support - For patients and families
    • Genetic Alliance (http://www.geneticalliance.org/ws_display.asp?filter=infosearch_results&info_keyword=Achondroplasia&expand=Treatment)
    • Human Growth Foundation (http://www.hgfound.org)
    • International Skeletal Dysplasia Registry, Cedars-Sinai Medical Center (http://www.csmc.edu/3805.html)
    • Little People of America, Inc. (http://www.lpaonline.org)
    • March of Dimes (http://www.marchofdimes.com/pnhec/4439_1204.asp)
    • National Organization for Rare Disorders (http://www.rarediseases.org/search/rdbdetail_abstract.html?disname=Achondroplasia)
    • Resource list from the University of Kansas Medical Center (http://www.kumc.edu/gec/support/dwarfism.html)
    • The MAGIC Foundation (http://www.magicfoundation.org/)

You may also be interested in these resources, which are designed for healthcare professionals and researchers.

  • Gene Reviews - Clinical summary (http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=achondroplasia)
  • Gene Tests - DNA tests ordered by healthcare professionals (http://www.genetests.org/query?testid=2789)
  • ClinicalTrials.gov - Linking patients to medical research (http://clinicaltrials.gov/search/condition=%22achondroplasia%22)
  • PubMed - Recent literature (http://www.ncbi.nlm.nih.gov/pubmed?term=(Achondroplasia[MAJR])+AND+(achondroplasia[TIAB])+AND+english[la]+AND+human[mh]+AND+"last+1440+days"[dp])
  • OMIM - Genetic disorder catalog (http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=100800)

What other names do people use for achondroplasia?

  • ACH
  • Achondroplastic dwarfism
  • Chondrodystrophia fetalis
  • Chondrodystrophy syndrome
  • Congenital osteosclerosis
  • Dwarf, achondroplastic
  • Osteosclerosis congenita

See How are genetic conditions and genes named? (http://ghr.nlm.nih.gov/handbook/mutationsanddisorders/naming) in the Handbook.

What if I still have specific questions about achondroplasia?

  • See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.
  • Ask the Genetic and Rare Diseases Information Center (http://rarediseases.info.nih.gov/GARD/).
  • Submit your question to Ask the Geneticist (http://www.askthegen.org/).

What glossary definitions help with understanding achondroplasia?

apnea ; autosomal ; autosomal dominant ; cartilage ; cell ; congenital ; dwarf ; dwarfism ; gene ; infection ; lordosis ; macrocephaly ; mutation ; new mutation ; ossification ; protein ; respiratory ; short stature ; stature ; syndrome ; tissue

You may find definitions for these and many other terms in the Genetics Home Reference Glossary (http://ghr.nlm.nih.gov/glossary).

References
  • Gene Review (http://www.ncbi.nlm.nih.gov/bookshelf/br.fcgi?book=gene&part=achondroplasia)
  • Horton WA, Lunstrum GP. Fibroblast growth factor receptor 3 mutations in achondroplasia and related forms of dwarfism. Rev Endocr Metab Disord. 2002 Dec;3(4):381-5. Review. No abstract available. (http://www.ncbi.nlm.nih.gov/pubmed/12424440?dopt=Abstract)
  • Horton WA. Recent milestones in achondroplasia research. Am J Med Genet A. 2006 Jan 15;140(2):166-9. No abstract available. (http://www.ncbi.nlm.nih.gov/pubmed/16353253?dopt=Abstract)
  • Scriver, Charles R; The metabolic & molecular bases of inherited disease; 8th ed.; New York : McGraw-Hill, c2001. p5379-5395.
  • Vajo Z, Francomano CA, Wilkin DJ. The molecular and genetic basis of fibroblast growth factor receptor 3 disorders: the achondroplasia family of skeletal dysplasias, Muenke craniosynostosis, and Crouzon syndrome with acanthosis nigricans. Endocr Rev. 2000 Feb;21(1):23-39. Review. (http://www.ncbi.nlm.nih.gov/pubmed/10696568?dopt=Abstract)

 

The resources on this site should not be used as a substitute for professional medical care or advice. Users seeking information about a personal genetic disease, syndrome, or condition should consult with a qualified healthcare professional. See How can I find a genetics professional in my area? (http://ghr.nlm.nih.gov/handbook/consult/findingprofessional) in the Handbook.

 
Reviewed: June 2006
Published: November 20, 2009