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Genetics Home Reference: your guide to understanding genetic conditions     A service of the U.S. National Library of Medicine®


Reviewed July 2008

What is hypochondrogenesis?

Hypochondrogenesis is a rare, severe disorder of bone growth. This condition is characterized by a small body, short limbs, and abnormal bone formation (ossification) in the spine and pelvis.

Affected infants have short arms and legs, a small chest with short ribs, and underdeveloped lungs. Bones in the skull develop normally, but the bones of the spine (vertebrae) and pelvis do not harden (ossify) properly. The face appears flat and oval-shaped, with widely spaced eyes, a small chin, and, in some cases, an opening in the roof of the mouth called a cleft palate. Individuals with hypochondrogenesis have an enlarged abdomen and may have a condition called hydrops fetalis in which excess fluid builds up in the body before birth.

As a result of these serious health problems, some affected fetuses do not survive to term. Infants born with hypochondrogenesis usually die at birth or shortly thereafter from respiratory failure. Babies who live past the newborn period are usually reclassified as having spondyloepiphyseal dysplasia congenita, a related but milder disorder that similarly affects bone development.

How common is hypochondrogenesis?

Hypochondrogenesis and achondrogenesis, type 2 (a similar skeletal disorder) together affect 1 in 40,000 to 60,000 newborns.

What genes are related to hypochondrogenesis?

Hypochondrogenesis is one of the most severe conditions in a spectrum of disorders caused by mutations in the COL2A1 gene. This gene provides instructions for making a protein that forms type II collagen. This type of collagen is found mostly in the clear gel that fills the eyeball (the vitreous) and in cartilage. Cartilage is a tough, flexible tissue that makes up much of the skeleton during early development. Most cartilage is later converted to bone, except for the cartilage that continues to cover and protect the ends of bones and is present in the nose and external ears. Type II collagen is essential for the normal development of bones and other connective tissues that form the body's supportive framework. Mutations in the COL2A1 gene interfere with the assembly of type II collagen molecules, which prevents bones and other connective tissues from developing properly.

Related Gene(s)

Changes in this gene are associated with hypochondrogenesis.

  • COL2A1

How do people inherit hypochondrogenesis?

Hypochondrogenesis is considered an autosomal dominant disorder because one copy of the altered gene in each cell is sufficient to cause the condition. It is caused by new mutations in the COL2A1 gene and occurs in people with no history of the disorder in their family. This condition is not passed on to the next generation because affected individuals do not live long enough to have children.

Where can I find information about diagnosis or management of hypochondrogenesis?

These resources address the diagnosis or management of hypochondrogenesis and may include treatment providers.

  • Genetic Testing Registry: Hypochondrogenesis (
  • MedlinePlus Encyclopedia: Achondrogenesis (

You might also find information on the diagnosis or management of hypochondrogenesis in Educational resources and Patient support.

General information about the diagnosis ( and management ( of genetic conditions is available in the Handbook. Read more about genetic testing (, particularly the difference between clinical tests and research tests (

To locate a healthcare provider, see How can I find a genetics professional in my area? ( in the Handbook.

Where can I find additional information about hypochondrogenesis?

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

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

What other names do people use for hypochondrogenesis?

  • achondrogenesis type II/hypochondrogenesis

For more information about naming genetic conditions, see the Genetics Home Reference Condition Naming Guidelines ( and How are genetic conditions and genes named? ( in the Handbook.

What if I still have specific questions about hypochondrogenesis?

Ask the Genetic and Rare Diseases Information Center (

What glossary definitions help with understanding hypochondrogenesis?

autosomal ; autosomal dominant ; bone formation ; cartilage ; cell ; cleft palate ; collagen ; dysplasia ; gene ; hydrops fetalis ; ossification ; palate ; pelvis ; protein ; respiratory ; spectrum ; tissue

You may find definitions for these and many other terms in the Genetics Home Reference Glossary.


  • Castori M, Brancati F, Scanderbeg AC, Dallapiccola B. Hypochondrogenesis. Pediatr Radiol. 2006 May;36(5):460-1. Epub 2006 Jan 24. (
  • Körkkö J, Cohn DH, Ala-Kokko L, Krakow D, Prockop DJ. Widely distributed mutations in the COL2A1 gene produce achondrogenesis type II/hypochondrogenesis. Am J Med Genet. 2000 May 15;92(2):95-100. (
  • Spranger J, Winterpacht A, Zabel B. The type II collagenopathies: a spectrum of chondrodysplasias. Eur J Pediatr. 1994 Feb;153(2):56-65. Review. (
  • Suzumura H, Kohno T, Nishimura G, Watanabe H, Arisaka O. Prenatal diagnosis of hypochondrogenesis using fetal MRI: a case report. Pediatr Radiol. 2002 May;32(5):373-5. Epub 2002 Mar 9. (


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? ( in the Handbook.

Reviewed: July 2008
Published: February 1, 2016