Last revised by Lee Hancox on 21 Jul 2017

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

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

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

There are several recognized subtypes:

Mutations in the SLC26A2 and COL2A1 genes cause achondrogenesis types 1B and 2, respectively. The genetic cause of achondrogenesis type 1A is still unknown. The patterns of inheritance are autosomal recessive in types 1A and 1B, and autosomal dominant with de-novo mutations in type B.

Sonographic diagnosis may be possible after 13 weeks of gestation, where nuchal edema may be evident as an early (though non-specific) sign.

The fetal bony structures are often unable to be identified. There may also be extreme micromelia 5. Calvarial ossification may be preserved with the type II subtype 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.

M Fracaro first described a case of achondrogenesis in 1952.

General considerations for mild cases include hypochondrogenesis. For absent calvarial bone(s) (type 1A/1B) on antenatal ultrasound, consider acrania.

  • achondroplasia: a common cause of dwarfism; not to be confused with achondrogenesis

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Cases and figures

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