Achondrogenesis refers to a group of rare and extreme skeletal dysplasias.

The estimated incidence is 1:40,000 with no recognised gender predilection.

It is classified as an osteochondrodysplasias, meaning deficiency of both bone and cartilage development.


There are several recognised sub types:


There are various patterns of inheritance ranging from autosomal dominant to autosomal recessive forms. Type II achondrogenesis is thought to be sporadic.

Antenatal ultrasound

Sonographic diagnosis may be possible after 13 weeks where nuchal oedema may be evident as an early (although non-specific) sign. 

The fetal bony structures are often unable to be identified. There may also be extreme micromelia 5. Calvarial ossification can be preserved with the type II sub type which can in turn give a floating head appearance.

Additional sonographic findings include:

Other ancillary sonographic features that may be present include:

The prognosis is generally poor with most infants being stillborn or dying soon after birth. 

General considerations for mild cases include hypochondrogenesis. For an absent calvarial bone(s) (type Ia/Ib) on antenatal ultrasound, consider acrania.

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Article Information

rID: 13275
Section: Pathology
Tag: cases
Synonyms or Alternate Spellings:
  • Achondrogenesis : general

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